1. Status of This Document
+ This specification was published by the [HydraCG]. +It is not a W3C Standard, nor it is on the W3C Standards Track. +Please note that under the W3C Community Contributor License Agreement (CLA) there is a limited opt-out and other conditions apply. +Learn more about W3C Community and Business Groups. +1.1. Conventions
+Within this document, the following namespace prefix bindings are used:
+| Prefix + | Namespace + |
|---|---|
| hydra: + | http://www.w3.org/ns/hydra/core# + |
| rdf: + | http://www.w3.org/1999/02/22-rdf-syntax-ns# + |
| rdfs: + | http://www.w3.org/2000/01/rdf-schema# + |
| xsd: + | http://www.w3.org/2001/XMLSchema# + |
| owl: + | http://www.w3.org/2002/07/owl# + |
| vs: + | http://www.w3.org/2003/06/sw-vocab-status/ns# + |
| dc: + | http://purl.org/dc/terms/ + |
| cc: + | http://creativecommons.org/ns# + |
| schema: + | http://schema.org/ + |
2. Introduction
+Note: This section is non-normative.
+Coping with the ever-increasing amount of data becomes increasingly +challenging. To alleviate the information overload put on people, +systems are progressively being connected directly to each other. +They exchange, analyze, and manipulate humongous amounts of data +without any human interaction. Most current solutions, however, +do not exploit the whole potential of the architecture of the World +Wide Web and completely ignore the possibilities offered by Linked Data +technologies.
+The combination of the REST architectural style, and the Linked +Data principles offer opportunities to advance the Web of machines +in a similar way that hypertext did for the human Web. Most +building blocks exist already and are in place, but they are rarely +used together. Hydra tries to fill that gap. It allows data +to be enriched with machine-readable affordances which enable interaction. +This not only addresses the problem that Linked Data is still mostly +read-only, but it also paves the way for a completely new breed +of interoperable Web APIs. The fact that it enables the creation +of composable contracts means that interaction models of Web APIs +can be reused at an unprecedented granularity.
+3. Hydra at a Glance
+Note: This section is non-normative.
+The basic idea behind Hydra is to provide a vocabulary which enables a +server to advertise valid state transitions to a client. A client can +then use this information to construct requests (i.e. compliant with +an HTTP protocol) which modify the server’s state so that a certain +desired goal is achieved. Since all the information about the valid state +transitions is exchanged in a machine-processable way at runtime +instead of being hardcoded into the client at design time, clients +can be decoupled from the server and adapt to changes more easily.
+The namespace of the Hydra core vocabulary
+is http://www.w3.org/ns/hydra/core#, and the suggested prefix
+is hydra. The figure below illustrates the vocabulary
+(the figure’s goal is to show how Hydra is used rather than its precise
+definition).
An alphabetical index of the classes and properties of Hydra +is given below. All the terms are hyperlinked to their detailed +description for quick reference.
+4. Using Hydra
+Throughout this section, a simple Web API featuring an issue tracker +will be used to illustrate how Hydra can be used. The Web API enables +its users to file new issues, modify or delete existing ones, and +to comment them. For the sake of simplicity, orthogonal aspects such +as authentication or authorization are not covered.
+4.1. Adding Affordances to Representations
+The exemplary Web API has to expose representations of issues and +comments. To enable interaction with those resources, a client has +to know which operations the server supports. In human-facing +websites such affordances are typically exposed by links and forms +and described in natural language. Unfortunately, machines can not +interpret such information easily. The solution that presents itself +is to reduce the language to a few unambiguous concepts which are easily +recognizable by a machine client. Hydra formalizes such concepts.
+The simplest and most important affordance on the Web are hyperlinks. +Without them, it would be impossible to browse the Web. +Users typically select the link based on the text it is labeled with. +To give machines a similar understanding, links can be annotated +with a link relation type—a registered token or a URI identifying +the semantics of the link. The following example shows how such +a typed link is used in HTML to reference a stylesheet.
++< link href = "http://www.example.com/styles.css" rel = "stylesheet" />
In Linked Data, the link relation type corresponds to the property itself. +An example in JSON-LD would thus look as follows.
++{ "urn:iana:link-relations:stylesheet" : { "@id" : "http://www.example.com/styles.css" } }
Generally, a client decides whether to follow a link or not based on +the link relation (or property in the case of Linked Data) which +defines its semantics. There are however also clients such as Web crawlers +which simply follow every link intended to be dereferenced. In HTML this +usually means that all links in anchor elements +(the <a> tag) are followed, but most references in link +elements (the <link> tag), such as used in the example +above, are ignored. Since in RDF serializations no such distinction exists, +the best a client can do is to blindly try to dereference all URIs. +It would thus be beneficial to describe in a machine-readable manner +if a property represents a link intended to be dereferenced or +solely an identifier. Hydra’s Link class does just that. It can be +used to define properties that represent dereferencable links. +In the exemplary Web API used throughout this section, it can be +used to define a property linking issues to their comments:
++{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/vocab#comments" , "@type" : "Link" }
In the example above, a property identified with the URL http://api.example.com/vocab#comments is defined to be
+of the type Link. This is enough information for a client understanding
+Hydra to know that the value of the comments property
+in the following example is intended to be dereferenced.
Note: It is recommended to dereference resources that are within an API’s domain. +This may prevent possible issues with cross-site scripting or obtaining +resources which might have no meaning to the client or such that the client +would be unable to interpret. Still, there is no formal prohibition of +dereferencing resources linked with well-known properties, e.g. rdf:seeAlso.
++{ "@context" : { "comments" : "http://api.example.com/vocab#comments" }, "@id" : "http://api.example.com/an-issue" , "title" : "An exemplary issue linking to its comments" , "comments" : { "@id" : "http://api.example.com/an-issue/comments" } }
In the example above, the value of the comments property
+is a JSON object with an @id member. This is JSON-LD’s
+convention to distinguish between strings and IRIs. By using JSON-LD’s
+type-coercion feature, the representation can be made even more idiomatic:
+{ "@context" : { "comments" : { "@id" : "http://api.example.com/vocab#comments" , "@type" : "@id" } }, "@id" : "http://api.example.com/an-issue" , "title" : "An exemplary issue linking to its comments" , "comments" : "http://api.example.com/an-issue/comments" }
While links are enough to build read-only Web APIs, more powerful +affordances are required to build read-write Web APIs. Thus, Hydra +introduces the notion of operations. Simply speaking, an Operation represents the information necessary for a client +to construct valid HTTP requests in order to manipulate the server’s +resource state. As such, the only required property of an Operation is its method. Optionally, it is also possible +to describe what information the server expects or returns, +including additional information about response status codes that +might be returned. This helps a developer to understand what to expect +when invoking an operation. This information has, however, +not to be considered as being complete; it is merely a hint. +Developers should, e.g., expect that other status codes might be returned +and program their clients accordingly.
+The following example illustrates how representations can be +augmented with information that enables clients to interact with +them.
++{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "/an-issue" , "title" : "An exemplary issue representation" , "description" : "This issue can be deleted with an HTTP DELETE request." , "operation" : [ { "@type" : "Operation" , "method" : "DELETE" } ] }
The example above references Hydra’s context to map properties such +as operation and method and values like Operation to URLs +that unambiguously identify these concepts. It would be similarly valid +JSON-LD if these mappings would be directly embedded into the representation +or if the full URLs would be used instead. Typically, however, the context +is the same for a lot of representations in a Web API and it thus makes +sense to reduce the response size by leveraging a remote context that +can easily be cached by a client.
+Note: It is worth mentioning that due to the fact that Hydra is built on +RDF, which is a graph, it may happen that a related resource +(an object of the relation) may not be fully described in the +resource’s payload.
+In several circumstances (i.e. payload terms defined in API documentation sa described in § 4.2 Documenting a Web API or IriTemplate expected as a related resource as described in Templated Links) client may +discover no additional statements describing it. These rules should +be considered by the client in following scenarios:
+-
+
-
+
in case of an object expected to be a hypermedia resource does not have +all the necessary statements for which it is a subject, the client +SHOULD look in the API documentation for more details
+ -
+
in case the mentioned object, after consulting +an API documentation, still does not have +all the necessary statements for which it is a subject and both +mentioned object’s Url and Url of the initially obtained resource +has the same scheme and authority (by means of [RFC3986] sections 3.1 and 3.2), the client SHOULD dereference that URL. +If the resource does not have the same scheme and authority the client +MAY chose to dereference it (for example if the resource originates +from another API well-known to the client)
+ -
+
in case the mentioned object still does not have all the necessary +statements for which it is a subject (i.e. dereferencing it failed +or statements are missing), the client SHOULD either ignore the whole +statement (i.e. for display purposes) or throw an exception +(i.e. an IriTemplate is about to be resolved and dereferenced)
+
Example of each of the situations are as follows:
++HTTP / 1.1 200 OK Content-Type : application/ld+json Link : <http://api.example.com/doc/>; rel="http://www.w3.org/ns/hydra/core#apiDocumentation" { "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@graph" : [{ "@id" : "http://api.example.com/attachments" , "@type" : "hydra:Collection" , "api:attachmentByIssue" : "api:AttachmentByIssueTemplate" }, { "@id" : "http://api.example.com/issues" , "@type" : "hydra:Collection" , "api:issueByName" : "api:IssueByNameTemplate" } }
+HTTP / 1.1 200 OK Content-Type : application/ld+json { "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@graph" : [{ "@id" : "api:AttachmentByIssueTemplate" , "@type" : "hydra:IriTemplate" , "template" : "http://api.example.com/attachments/{issue}" , ...}] }
where:
+-
+
-
+
resource
+http://api.example.com/attachmentsshould have +an IriTemplate available as there is a complete definition +of the template available athttp://api.example.com/doc/ -
+
resource
+http://api.example.com/issuesshould not have +an IRI template exposed as there are no additional details available, +neither in the initial resources' payload nor in the API documentation
Note: Keep in mind that any resource described by any hypermedia control +may fail at runtime due to various reasons. Operation details +such as returns or possibleStatus may also vary at runtime, +which means client SHOULD always verify received payloads at runtime.
+4.2. Documenting a Web API
+In Web APIs, most representations are typically very similar. +Furthermore, resources often support the same operations. It thus +makes sense, to collect this information in a central documentation. +Traditionally, this has been done in natural language which forces +developers to hardcode that knowledge into their clients. Hydra +addresses this issue by making the documentation completely +machine-processable. The fact that all definitions can be identified +by URLs enables reuse at unprecedented granularity.
+Hydra’s ApiDocumentation class builds the foundation for +the description of a Web API. As shown in the following example, +Hydra describes an API by giving it a title, a short description, and +documenting its main entry point. Furthermore, the classes known to +be supported by the Web API and additional information about status +codes that might be returned can be documented. This information +may be used to automatically generate documentations in natural +language.
++{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/doc/" , "@type" : "ApiDocumentation" , "title" : "The name of the API" , "description" : "A short description of the API" , "entrypoint" : "URL of the API’s main entry point" , "supportedClass" : [ // "... Classes known to be supported by the Web API ..." ], "possibleStatus" : [ // "... Statuses that should be expected and handled properly ..." ] }
In Linked Data, properties are, just as everything else, identified +by IRIs and thus have global scope which implies that they have +independent semantics. In contrast, properties in data models as +used in common programming languages are class-dependent. Their +semantics depend on the class they belong to. In data models classes +are typically described by the properties they expose whereas in +Linked Data properties define to which classes they belong. If no +class is specified, it is assumed that a property may apply to every +class.
+These differences have interesting consequences. For example, the +commonly asked question of which properties can be applied to an +instance of a specific class can typically not be answered for +Linked Data. Strictly speaking, any property which is not explicitly +forbidden could be applied. This stems from the fact that Linked Data +works under an open-world assumption whereas data models used by +programmers typically work under a closed-world assumption. The +difference is that when a closed world is assumed, everything that +is not known to be true is false or vice-versa. With an open-world +assumption the failure to derive a fact does not automatically imply +the opposite; it embraces the fact that the knowledge is incomplete.
+Since Hydra may use classes to describe the information expected or +returned by an operation, it also defines a concept to describe the +properties known to be supported by a class. The following example +illustrates this feature. Instead of referencing properties directly, supportedProperty references an intermediate data structure, +namely instances of the SupportedProperty class. This makes +it possible to define whether a specific property is required or +whether it is read-only or write-only depending on the class it is +associated with.
++{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/doc/#Comment" , "@type" : "Class" , "title" : "The name of the class" , "description" : "A short description of the class." , "supportedProperty" : [ // "... Properties known to be supported by the class ..." { "@type" : "SupportedProperty" , "property" : "#property" , // "The property" "required" : true , // "Is the property required in a request to be valid?" "readable" : false , // "Can the client retrieve the property’s value?" "writable" : true // "Can the client change the property’s value?" } ] }
All instances of a specific class typically support the same operations. +Hydra therefore features a supportedOperation property which defines +the operations supported by all instances of a class.
++{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/doc/#Comment" , "@type" : "Class" , "title" : "The name of the class" , "description" : "A short description of the class." , "supportedProperty" : [ // "... Properties known to be supported by the class ..." ], "supportedOperation" : [ // "... Operations known to be supported by instances of the class ..." ] }
The same feature can be used to describe the operations supported +by values of a Link property. This is often helpful when +certain operations depend on the permissions of the current user. It +makes it, e.g., possible to show a "delete" link only if the current +user has the permission to delete the resource. Otherwise, the link +would simply be hidden in the representation.
+Example shown below describes the operation’s expected and returned +value as a dereferencable resource (an RDF resource of a given class), +but the vocabulary is not limited to only those originating +from RDF and is enabled to other types of resources. +Please note that in case of multiple either returned or expected types +provided, client SHOULD assume the set includes any of the types, +but not limited to those types and client SHOULD interpret a received +payload at runtime for possible discrepancies.
++{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/doc/#comments" , "@type" : "Link" , "title" : "Comments" , "description" : "A link to comments with an operation to create a new comment." , "supportedOperation" : [ { "@type" : "Operation" , "title" : "Creates a new comment" , "method" : "POST" , "expects" : "http://api.example.com/doc/#Comment" , "returns" : "http://api.example.com/doc/#Comment" , "possibleStatus" : [ // "... Statuses that should be expected and handled properly ..." ] } ] }
Note: It is worth to mention that Hydra comes with a notion +of a dereferenceability promise, which means that resources marked +with a Resource class can be safely dereferenced by a client. +Unfortunately, the way how the Word Wide Web works it is impossible to +guarantee that the resource finally will be obtained.
+In addition to expected/returned resources, +it is also possible to express similar features for headers with returnsHeader and expectsHeader predicates which provides +a simple set of header names. Client SHOULD apply respective header +semantics when creating or receiving a request natural for the protocol in use.
++{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/doc/#comments" , "@type" : "Link" , "supportedOperation" : [ { "@type" : "Operation" , "method" : "POST" , "expects" : "http://api.example.com/doc/#Comment" , "returns" : "http://api.example.com/doc/#Comment" , "returnsHeader" : [ "Content-Type" , "Content-Length" ], "expectsHeader" : [ "Authorization" ] } ] }
The example above enable an HTTP client to prepare a proper cross-site +pre-flight request, so the server exposes enlisted headers for the client. +The client is also aware of the user authentication requirement necessary +for the operation invocation.
+For more complex scenarios it is also possible to expand selected header +specification with both name and possible values, i.e. when defining +expected Content-Type values of resources that can be uploaded. +In case multiple possible values are provided, client SHOULD assume +that the set includes any of the values, but not limited to those values. +In order to change that default behavior it is possible to use closedSet predicate on the header specification indicating that the set of provided +values is, well, closed and no other values are available. In both cases +the client SHOULD interpret a received payload at runtime for possible +discrepancies.
++{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/doc/#comments" , "@type" : "Link" , "supportedOperation" : [ { "@type" : "Operation" , "method" : "POST" , "expects" : "http://api.example.com/doc/#Upload" , "returns" : "http://api.example.com/doc/#Comment" , "returnsHeader" : [ { "headerName" : "Content-Type" , "possibleValue" : [ "text/turtle" , "application/ld+json" ] } "Content-Length" ], "expectsHeader" : [ "Authorization" , { "headerName" : "Content-Type" , "possibleValue" : [ "image/gif" , "image/png" ] } ] } ] }
To wrap up everything altogether, it is also possible to attach atomic +operations supported by, well, supported property itself. This might +come in handy for scenarios, when resource can be partially modified. +It can be achieved with two approaches, both having advantages and +disadvantages.
+First approach would involve adding a supportedOperation to the +intermediate structure of SupportedProperty. +This way prevents from leaking API specific features from the API itself +to i.e. externally defined properties. Data aggregators won’t assume that +each instance with a given property could have such an operation.
+Another approach would require the API to elevate a specific property +to Link, which can accept a supportedOperation. This +is more intuitive in APIs operating with internally used vocabularies +where assumption that every instance with that very specific property +has the operation attached available.
+Direct usage of supportedOperation on rdf:Property without elevating it to the Link SHOULD NOT be implemented as clients +may not discover such a construct correctly.
+There are rare situations when some supported operations once announced in the +API documentation should be retracted, i.e. to reflect current state of the +application or current user capabilities (or lack of them). It is doable +with the retractedOperation predicate that can be added to the reasorce +the same way as the operation is. By default all operations are available +without limits and it is up for the server to change that, and for the client +to discover any discrepancies compared against the API documentation in the runtime. +Yet server may want to inform the client that at the very moment an operation is either Unavailable or Unauthorized with a reason predicate. +The latter MAY be used to notify client that the user used to invoke +the request that provides operation availability information is currently +not authorized for that very operation to be invoked. The former on the other hand +MAY be used to inform that the operation is currently forbidden and client +SHOULD NOT invoke it. Server MAY also provide more custom reasons for which +the operation is not available but it SHOULD provide at least one of the +_Hydra_ built in reasons.
+The retractedOperation MUST NOT be used in context of the ApiDocumentation. +The retractedOperation predicate also MUST take precedence over both operation and supportedOperation declaration and overrides them. +The operation that comes with retractedOperation predicate SHOULD be identified +using any of the below enlisted methods:
+-
+
-
+
Iri by using object predicate
+ -
+
exact match of a resource described by possibleStatus, method, expects, returns or combination of those
+
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/doc/#comments" , "@type" : "Link" , "supportedOperation" : [ { "@type" : "Operation" , "method" : "POST" , "expects" : "http://api.example.com/doc/#Upload" }, { "@type" : "Operation" , "method" : "POST" , "expects" : "http://api.example.com/doc/#Comment" } ] }
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/doc/" , "@type" : "Collection" , "retractedOperation" : [ { "@type" : "Operation" , "method" : "POST" , "expects" : "http://api.example.com/doc/#Upload" , "reason" : "Unavailable" } ] }
In the example above the operation that expects an uploaded file became Unavailable, while the one expecting a comment remains available as +the expects predicate does not match any supported operations. +It is still recommended to mark operations being subject for further +restrictions with an Iri as from the client perspective this may be +easier to implement simple literal Iri comparison rather than to compare +graphs of objects.
+Note: These are the simple example scenarios and possible usages are not +limited to those described above.
+Due to the fact an ApiDocumentation as all other resources may fail +at runtime, it is important to take countermeasures. A simple strategy +to try to recover from such a situation would be to reload +the ApiDocumentation and redo all pre-computations that were +based on the ApiDocumentation (or at least those that lead +to the current failure). Another, simpler approach would require +an application to show an error message with option to return +to a previous or home screen.
+Hydra also allows enriching both ApiDocumentation and +hypermedia controls with human-readable descriptions by applying title and description (as shown in the examples above). +The former states a name of such a decorated element that could +be displayed as a label. The latter provides its description +to be presented i.e. as a hint.
+Aforementioned title and description SHOULD take precedence +over standard rdfs:label and rdfs:comment.
+There is one more feature related to how Linked Data works. Consider the +example below written in turtle syntax:
++# An example API documentation itself with all the standard bits @base <http://some.app/> . @prefix api: <http://some.api/> . @prefix ex: <http://ontology.example/> . @prefix hydra: <http://www.w3.org/ns/hydra/core> . @prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> . <api> a hydra : ApiDocumentation ; hydra : supportedClass api : ClassOne , api : ClassTwo . # Anything else ex : SomeType a rdfs : Class .
...and how it could be transformed with JSON-LD framing process:
++{ "@context" : { ...}, "@graph" : [ { "@id" : "http://some.app/api" , "@type" : "hydra:ApiDocumentation" , "hydra:supportedClass" : [ { "@id" : "api:ClassTwo" }, { "@id" : "api:ClassOne" } ] } ] }
As you can see, additional details about ex:SomeType went +missing, while this shouldn’t happen. The fact that the IRI mentioned +is an rdfs:Class may be meaningful for a correct interpretation +of the received payload and this is a sole reason of why a Client +SHOULD NOT disregard other parts of the payload that are not directly +related to the API documentation or other hypermedia controls.
+4.3. Discovering a Hydra-powered Web API
+The first step when trying to access a Web API is to find an entry
+point. Typically, this is done by looking for a documentation on the
+API publisher’s homepage. Hydra enables the API’s main entry point
+to be discovered automatically if the API publisher marks his
+responses with a special HTTP Link Header as defined in [RFC8288].
+A Hydra client would look for a Link Header with a relation type http://www.w3.org/ns/hydra/core#apiDocumentation (this is
+the IRI identifying the apiDocumentation property).
In the following example, a Hydra client simply accesses the
+homepage of an API publisher (http://www.example.com/)
+to find the entry point of its API. A client may use an HTTP GET or
+HEAD request. The difference between the two is that the former may
+return a message-body in the response whereas the latter will not;
+otherwise they are identical.
+HEAD / HTTP / 1.1 Host : www.example.com
+HTTP / 1.1 200 OK ...Content-Type: text/html; charset=utf-8Link: <http://api.example.com/doc/>; rel="http://www.w3.org/ns/hydra/core#apiDocumentation"
The response in the example above contains an HTTP Link Header
+pointing to http://api.example.com/doc/. Retrieving that resource,
+the client would obtain a Hydra API documentation defining the API’s main entry point:
+GET /doc/ HTTP / 1.1 Host : api.example.com Accept : application/ld+json
+HTTP / 1.1 200 OK ...Content-Type: application/ld+json{ "@context": "http://www.w3.org/ns/hydra/context.jsonld", "@id": "http://api.example.com/doc/", "title": "The example.com API", "entrypoint": "http://api.example.com/", ...}
Note: Please note that in some cases the entry point will already be +known to the client. Thus, the discovery of the API documentation +using HTTP Link Headers may not be necessary as the concepts +used in responses from the API will dereference to their documentation.
+In another scenario the ApiDocumentation would be discovered from +a bookmarked resource’s representation. +The API implementation SHOULD emit the HTTP Link header on every API response, making the ApiDocumentation (and entry +points it defined) discoverable all the time.
++GET /api/items HTTP / 1.1 Host : api.example.com Accept : application/ld+json
+HTTP / 1.1 200 OK ...Content-Type: application/ld+jsonLink: <http://api.example.com/doc/>; rel="http://www.w3.org/ns/hydra/core#apiDocumentation"{ "@context": "http://www.w3.org/ns/hydra/context.jsonld", "@id": "http://api.example.com/api/items", "title": "Items collection", ...}
4.4. Api versions
+It is common to provide a separate API address after a breaking changes +update. This prevents current clients not to get broken as these may not +support these changes.
+With hypermedia provided in each response payload, it may be unnecessary +to provide such an alternative API. This is due to fact the client follows +what the server provides and with proper margin for errors implemented +within that client, even breaking changes can be published on the fly.
+Still, Hydra does neither have any special support for API versions, nor +prevents them. It’s fully an implementers decision on if and how +to provide the API features.
+5. Advanced Concepts
+5.1. Collections
+In many situations, it makes sense to expose resources that reference +a set of somehow related resources. Results of a search query or +entries of an address book are just two examples. To simplify such +use cases, Hydra defines the two classes Collection and PartialCollectionView.
+A Collection can be used to reference a set of resources +as follows:
++{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/an-issue/comments" , "@type" : "Collection" , "totalItems" : 4980 , "member" : [ { "@id" : "/comments/429" }, { "@id" : "/comments/781" , "title" : "Properties may be embedded directly in the collection" }, ...] }
As shown in the example above, member items can either consist of +solely a link or also include some properties. In some cases embedding +member properties directly in the collection is beneficial as it may +reduce the number of HTTP requests necessary to get enough information +to process the result.
+Since collections may become very large, Web APIs often chose to +split a collection into multiple pages. In Hydra, that can be achieved +with a PartialCollectionView. It describes a specific +view on the collection which represents only a subset of the collection’s +members. A PartialCollectionView may contain links to the first, next, previous, and last PartialCollectionView which allows a client to find all members +of a Collection.
++{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/an-issue/comments" , "@type" : "Collection" , "totalItems" : 4980 , "member" : [ // "... a subset of the members of the Collection ..." ], "view" : { "@id" : "http://api.example.com/an-issue/comments?page=3" , "@type" : "PartialCollectionView" , "first" : "/an-issue/comments?page=1" , "previous" : "/an-issue/comments?page=2" , "next" : "/an-issue/comments?page=4" , "last" : "/an-issue/comments?page=498" } }
Note: It is worth to mention that all those links are optional, +and it is up to server whether to provide these links or not.
+5.2. Member assertions
+A memberAssertion (formerly manages) is a way to declare additional,
+implicit statements about members of a collection.
+Statements which may otherwise be missing from the respective member
+resources inlined in a collection’s representation.
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/an-issue/comments" , "@type" : "Collection" , "memberAssertion" : { "subject" : "http://api.example.com/an-issue" , "property" : "http://api.example.com/vocab#comment" }, "member" : [ { "@id" : "/comments/429" } ] }
In the above example, adding a memberAssertion node to the collection
+instructs the client that every member of this collection is linked
+to the subject by the property. It could be written as a SPARQL
+triple pattern below, where ?m would be substituted by each member
+of the collection.
<http://api.example.com/an-issue> <http://api.example.com/vocab#comment> ?m A memberAssertion MUST use two and only two of the subject, property and object predicates. The memberAssertion predicate +MAY have more than one such blocks, each expressing different relations +between the collection members and other resources.
+Note: It’s important to point out that the subject, property and object predicates are defined within the Hydra namespace +and are not rdfs terms.
+It is also possible to use memberAssertion predicate on the
+API documentation level, by attaching this predicate to subclasses
+of the Collection, like in the example below. Clients would
+understand that all members of collections which are instances
+of api:UserCollections would in fact have rdf:type api:User.
+{ "@context" : [ "http://www.w3.org/ns/hydra/context.jsonld" , { "api" : "http://api.example.com/api/documentation#" } ], "@id" : "http://api.example.com/api/documentation" , "@type" : "ApiDocumentation" , "supportedClass" : [ "api:User" , "api:UserCollection" ], "api:UserCollection" : { "subClassOf" : "Collection" , "memberAssertion" : { "property" : "rdf:type" , "object" : "api:User" }, } }
It is worth to mention that a strongly typed collection instance can have +its own member assertions. In such a scenario, both API documentation level and instance +level assertions should be combined as neither makes the other obsolete.
+More complex scenario would involve a class hierarchy, in which each class +can carry additional member assertions compared to it’s base class. +To discover all available member assertion blocks client SHOULD traverse +whole class hierarchy to gather all the member assertions. In order +to take such a burden from clients it is strongly recommended providing +all member assertion blocks to be provided on each class level including +its base class blocks, so the client does not have to perform +this traversing behavior.
+5.3. Templated Links
+Sometimes, it is impossible for a server to construct a URL because +the URL depends on information only known by the client. A typical +use case are URLs which enable a client to query the server. In such +a case, the server cannot construct the URL because it does not know +the query the client is interested in. What the server can do however, +is to give the client a template to construct such a URL at runtime. +In Hydra, the IriTemplate class is used to do so.
+An IriTemplate consists of a template literal and a set +of mappings. Each IriTemplateMapping maps a variable used in the template to a property and may +optionally specify whether that variable is required or not. +The syntax of the template literal is specified by its datatype and +defaults to the [RFC6570] URI Template syntax, which can be +explicitly indicated by Rfc6570Template.
++{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@type" : "IriTemplate" , "template" : "http://api.example.com/issues{?q}" , "variableRepresentation" : "hydra:BasicRepresentation" , "mapping" : [ { "@type" : "IriTemplateMapping" , "variable" : "q" , "property" : "hydra:freetextQuery" , "required" : true } ] }
The example above maps the variable q to Hydra’s freetextQuery property and marks it as required. As its name suggests,
+the freetextQuery property can be used for free text queries.
A template syntax only details how to fill out simple string values, +but not how to derive such string values from typed values, +language-tagged strings, or IRIs. Hydra addresses this by +specifying how such values are to be serialized as strings. The +serialization of an IriTemplate’s variables can be described +by setting the variableRepresentation property to BasicRepresentation or ExplicitRepresentation. The BasicRepresentation represents values by their lexical form. It +omits type and language information and does not differentiate between +IRIs and literals. The ExplicitRepresentation, on the other +hand, includes type and language information and differentiates +between IRIs and literals by serializing values as follows:
+-
+
-
+
IRIs are represented as-is
+ -
+
literals, i.e., (typed) values and language-tagged strings are +represented by their lexical form, surrounded by a single pair of +doubles quotes (
+") -
+
if a literal has a language, a single
+@symbol is +appended after the double-quoted lexical form, followed by a +non-empty [BCP47] language code -
+
if a literal has a type, two caret symbols (
+^^) are appended +after the double-quoted literal, followed by the full datatype IRI
In both representations characters MUST NOT be escaped. In case the +representation format is not explicitly described, clients SHOULD +use the BasicRepresentation by default.
+ Warning: Although ExplicitRepresentation use of @ and ^^ is similar, it is not the same as the [Turtle] representation for literals. Turtle literals require escaping
+of special characters, surround datatype IRIs with angular brackets
+(< and >), and also allow single quotes (') to indicate literals.
+The ExplicitRepresentation values must not be escaped,
+IRIs must not be surrounded by any character, and only double quotes
+can indicate literals.
Below are some example values serialized in the different
+representations as well as the result of expanding the IRI template http://example.com/find/{value} with the respective value.
The example Description of an IRI Template that was already mentioned +uses a variableRepresentation on the whole IriTemplate, but +each mapped variable represented as an IriTemplateMapping can have +its own variableRepresentation declaration. It MUST override +the declaration from the IriTemplate level for that very IriTemplateMapping as it takes precedence. The example below +depicts such a situation:
++{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@type" : "IriTemplate" , "template" : "http://api.example.com/issues{?q,category}" , "variableRepresentation" : "ExplicitRepresentation" , "mapping" : [ { "@type" : "IriTemplateMapping" , "variable" : "q" , "property" : "hydra:freetextQuery" , "variableRepresentation" : "BasicRepresentation" , "required" : true }, { "@type" : "IriTemplateMapping" , "variable" : "category" , "property" : "schema:category" } ] }
In this example, the variable category will be serialised using the explicit representation, +derived from the template itself. The variable q on the other hand will override that +to use basic representation.
+Similar to how Hydra’s Link class allows the definition of +properties that represent hyperlinks as described in § 4.1 Adding Affordances to Representations, the TemplatedLink class +allows the definition of properties whose value are IRI templates. +Hydra predefines one such property, namely the search property which +can be used to document available search interfaces.
++{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "hydra:search" , "@type" : "hydra:TemplatedLink" }
IRI expansion should be performed with respect to the specification +behind the IRI template type ([RFC6570] by default), and the product +of this process SHOULD be an IRI. When the produced IRI is relative, +the client SHOULD stick to [RFC3986] sections 5.1.3 and 5.1.4 +to be compatible with most RDF serializations that support relative IRIs. +Still, it may be preferred to use another base URI for the expansion +process, which makes the resolveRelativeUsing term useful. It allows +to switch the IRI template expansion algorithm, so the base URI +is established using current link context, which is a subject +of the relation pointing to an IriTemplate instance. In case +that subject is a relative URI, default behavior SHOULD be used as fallback.
+The example below allows to make the product of an IRI template
+expansion relative to the http://api.example.com/an-issue/ resource
+by using it as its base URI, which further enables the some:operation to be moved to i.e. API documentation level rather
+to inline it.
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/an-issue/" , "@type" : "Collection" , "some:operation" : { "@type" : "IriTemplate" , "template" : "{id}" , "resolveRelativeUsing" : "LinkContext" , "variable" : "id" , "mapping" : { ...} } }
When constructed, the IRI would effectively become similar
+to http://api.example.com/an-issue/1234, with the relative part {id} appended to the link context URL.
5.4. IRI template operations
+There are circumstances in which client would like to perform an operation +not knowing the final IRI of the resource to be called. This case +is especially in force when working with collections - client may want +to add a new collection member, or it may need to provide more details +while searching with other protocol’s method (i.e. POST instead of GET +in case of an HTTP).
+This is achievable by attaching a supportedOperation to the property +that connects a subject of that relation with its IriTemplate as described in the previous part of this document. Please note that +client is still allowed to use the defined link and custom operation’s +method is optional.
++{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api-documentation" , "@type" : "ApiDocumentation" , "api:search" : { "@type" : "Link" , "rdfs:subClassOf" : "search" , "supportedOperation" : { "@type" : "SupportedOperation" , "method" : "POST" } } }
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/issues" , "@type" : "Collection" , "api:search" : { "@type" : "IriTemplate" , "template" : "/issues?search={name}" , "mapping" : { ...} } }
The example above allows client to either invoke an HTTP GET or POST
+call on http://api.example.com/issues?search=search_string resource.
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api-documentation" , "@type" : "ApiDocumentation" , "api:find" : { "supportedOperation" : { "@type" : "SupportedOperation" , "method" : "POST" } } }
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/issues" , "@type" : "Collection" , "api:search" : { "@type" : "IriTemplate" , "template" : "/issues?find={name}" , "mapping" : { ...} } }
The example above allows client to invoke only an HTTP POST
+call on http://api.example.com/issues?find=search_string resource as
+the described relation of find is not a Link.
5.5. Supported property data source
+There are circumstances in which an API would like to inform a client on +when to obtain values to feed data structures with details. Having all the +necessary components like supported property, collection and IRI templates, +it is possible to drive the client and direct it with links and operations +to the data sources.
+It is doable by attaching either a collection or search predicate to instance of supportedProperty or to property. +In such case client SHOULD assume that the relation leads to +the collection of values compatible with the supported property’s range +and can be used to feed data structures with the supported property. +It is recommended (but not mandatory) to use freetextQuery variable mapping in case of the search predicate as it has a +well-defined semantics and takes the burden of interpretation from +the client.
+While it is possible to provide such links in both API documentation and within the received payload, +client SHOULD use the latter link first if applicable. +This is due to the fact the server may want to put additional +context to narrow the collection of viable values. Redefinition does not +make the more general one obsolete though and can be used as a fallback.
++{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@type" : "ApiDocumentation" , "supportedClass" : { "@id" : "schema:Event" , "supportedProperty" : { "property" : "schema:actor" , "search" : { "template" : "/api/user{?search}" , "mapping" : { "variable" : "search" , "property" : "freetextQuery" } } } }, ...}
The example above instructs a client that every resource of type schema:Event can have a relation of schema:actor, the objects
+of which the client can obtain using the search link provided.
5.6. Description of HTTP Status Codes and Errors
+In case of the HTTP protocol, status codes have well-defined semantics
+and can be used to signal the outcome of an operation. Unfortunately,
+however, HTTP status codes by themselves are often not specific enough,
+making it difficult to understand the real cause of an error. For instance,
+a 429 Too Many Requests response is rarely informative enough by itself.
+To address this issue, Hydra defines a Status class which allows
+additional information to be associated with the HTTP status code.
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@type" : "Status" , "statusCode" : 429 , "title" : "Too Many Requests" , "description" : "A maximum of 500 requests per hour and user is allowed." , ...}
An ApiDocumentation or an Operation may document the +status codes that might be returned by the server using the possibleStatus property as described in § 4.2 Documenting a Web API. +This allows a developer to understand what to expect when invoking +an operation. It has, however, not to be considered as an extensive +list of all potentially returned status codes; it is merely a hint. +Developers should expect to encounter other HTTP status codes as well.
+A server may also return a Status directly in a response. +When doing so, it often makes sense to subclass the Status to make its semantics more explicit. Hydra defines just one such subclass, +namely the Error class. This provides an extensible framework +to communicate error details to a client.
+Furthermore, a Status or Error returned by the server can also +be given an identifier. When dereferenced, the Error resource +can provide more detailed information or possible ways to resolve +the problem, if applicable.
+Finally, the server SHOULD provide error descriptions using an [RFC9457] standard by using an application/problem+json response. When doing so,
+the server also MUST provide an additional header pointing to either
+the built-in Hydra http://www.w3.org/ns/hydra/error context
+or any JSON-LD context that maps the terms type, title, detail, status and instance the same way as the standard one.
+HTTP / 1.1 400 Bad Request Content-Type : application/problem+json Link : <http://www.w3.org/ns/hydra/error>; rel="http://www.w3.org/ns/json-ld#context" { "type" : "https://example.com/probs/out-of-credit" , "@type" : "http://www.w3.org/ns/hydra/core#Error" , "title" : "You do not have enough credit." , "detail" : "Your current balance is 30, but that costs 50." , "instance" : "/account/12345/msgs/abc" , "balance" : 30 , "accounts" : [ "/account/12345" , "/account/67890" ] }
While the built-in context makes the response fully compatible with
+the mentioned specification, properties not defined in the standard
+Hydra’s error context won’t be visible for Hydra aware processors.
+To overcome this, it is possible to declare a custom context pointed
+the same way, that would combine standard Hydra’s standard error context
+and an additional JSON-LD context with either the @vocab or custom
+property mappings telling the processor on how to interpret those custom
+error properties.
Resources provided may have an additional hint pointing to an Error type like in the example above, but it is not mandatory to do so as all
+resources described with application/problem+json are considered Error.
Note: It is worth to mention that it may happen (i.e. due to proxy behavior) +the value of the status property will differ to the one received +from the protocol layer.
++HTTP / 1.1 400 Bad Request Content-Type : application/ld+json { "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@type" : "Error" , "@id" : "http://api.example.com/error-details/1234" , "title" : "An error occurred" , "description" : "Typically, a specialization of this class is used in practice." , ...}
5.7. Client initiated pagination
+There are situations when a client would like to provide a specific +collection limitations, i.e. by providing query-language like member +offset and limit, or some specific page index and number of members +per page. This is doable with offset/limit or pageIndex/limit predicates.
+With those, it is possible to bind a template variables mapped +with externally obtained values (i.e. user interaction) the same way +as with other mappings.
+While the predicates enlisted above accepts non-negative integer +numbers, there is also a possibility of providing a custom page +reference expressed via pageReference predicate. It is possible +to provide a custom page identifier (i.e. a GUID or a letter) +instead of a number.
+5.8. Extensions
+While Hydra Core Vocabulary allows addressing many usage scenarios, +not every aspect of API behavior can be covered. This +applies especially to querying, resource projection or data structure +description. This is due to fact that Hydra is meant to be as light +as possible forcing to drop some features out of its scope.
+That is why there is a possibility of hinting a client on what kind +of extensions may be found or used in the received payloads. +After discovering an extension predicate in the API documentation, client can assume additional +details are available described with complementary vocabularies.
++{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/doc/" , "@type" : "ApiDocumentation" , "title" : "The name of the API" , "description" : "A short description of the API" , "entrypoint" : "URL of the API’s main entry point" , "extension" : "http://www.w3.org/ns/shacl#" , ...}
It is up to the used vocabulary to define how these additional details +should be interpreted. In case client does not recognize these extensions, +additional details should be ignored and base Hydra interpretation +should be in force.
+Server SHOULD NOT use extensions to add statements that are in +contradiction to base Hydra interpretation, so the client is not confused. +Server SHOULD also keep multiple extensions describing adequate +knowledge in line regarding their description (i.e. data structure +descriptions in various vocabularies should not cause differences).
+Client can express its preferences through the Prefer HTTP header
+by pointing the preferred extensions via IRIs as on the example below.
+The client SHOULD use the Prefer HTTP header [RFC7240] with
+the hydra.extension preference as an iri attribute having
+the IRI of the extension as value to hint the server about the extension
+it supports. Multiple preferences can be expressed by providing multiple Prefer header values.
+GET http://api.example.com/api/people HTTP / 1.1 Prefer : hydra.extension; iri="http://schema.org/"
Server MUST implement Prefer header handling according to
+the [RFC7240] and implementers should proceed with caution.
6. Classes
+6.1. hydra:ApiDocumentation
+| Name: + | ApiDocumentation + |
|---|---|
| Summary: + | The Hydra API documentation class. + |
| Sub-class of: + | Resource + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api?documentation" , "@type" : "ApiDocumentation" , "entrypoint" : "http://api.example.com/api" , "extension" : "https://w3id.org/hydra/extension#shacl" , "supportedClass" : [ { "@id" : "http://api.example.com/vocab#User" , "title" : "User" , "description" : "Describes a system user." , "supportedOperation" : [ { "method" : "PUT" , "title" : "Create new user" , "description" : "Creates a brand new user." , "expects" : "http://api.example.com/vocab#User" , "returns" : "http://api.example.com/vocab#User" , "returnsHeader" : [ { "headerName" : "Content-Type" , "possibleValue" : [ "text/turtle" , "application/ld+json" ], "closedSet" : true } "Content-Length" ], "expectsHeader" : [ "Authorization" , { "headerName" : "Content-Type" , "possibleValue" : [ "image/gif" , "image/png" ], "closedSet" : true } ] } ], "supportedProperty" : [ { "property" : "http://api.example.com/vocab#login" , "writable" : true , "readable" : true , "required" : true } ] } ] }
6.2. hydra:BaseUriSource
+| Name: + | BaseUriSource + |
|---|---|
| Summary: + | Provides a base abstract for base Uri source + for Iri template resolution. + |
| Sub-class of: + | Resource + |
| Named instances: + | Rfc3986, LinkContext + |
6.3. hydra:Class
+| Name: + | Class + |
|---|---|
| Summary: + | The class of Hydra classes. + |
| Sub-class of: + | rdfs:Class
+ |
6.4. hydra:Collection
+| Name: + | Collection + |
|---|---|
| Summary: + | A collection holding references to a number of related resources. + |
| Sub-class of: + | Resource + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api/posts" , "@type" : "Collection" , "view" : { "@id" : "http://api.example.com/api/posts?skip=10" , "@type" : "PartialCollectionView" , "first" : "http://api.example.com/api/posts" , "last" : "http://api.example.com/api/posts?skip=100" , "previous" : "http://api.example.com/api/posts" , "next" : "http://api.example.com/api/posts?skip=20" , "totalItems" : 10 , }, "totalItems" : 100 , "member" : [ { "@id" : "http://api.example.com/api/posts/10" }, { "@id" : "http://api.example.com/api/posts/11" }, { "@id" : "http://api.example.com/api/posts/12" }, { "@id" : "http://api.example.com/api/posts/13" }, { "@id" : "http://api.example.com/api/posts/14" }, { "@id" : "http://api.example.com/api/posts/15" }, { "@id" : "http://api.example.com/api/posts/16" }, { "@id" : "http://api.example.com/api/posts/17" }, { "@id" : "http://api.example.com/api/posts/18" }, { "@id" : "http://api.example.com/api/posts/19" } ], "search" : { "template" : "/api/posts{?search,limit,offset}" , "resolveRelativeUsing" : "hydra:Rfc3986" , "mapping" : [ { "variable" : "search" , "property" : "hydra:freetextQuery" , "required" : true , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "limit" , "property" : "hydra:limit" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "offset" , "property" : "hydra:offset" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" } ] } }
6.5. hydra:Error
+| Name: + | Error + |
|---|---|
| Summary: + | A runtime error, used to report information beyond the returned + status code. + |
| Sub-class of: + | Status + |
+HTTP / 1.1 400 Bad request Content-Type : application/problem+json Link : <http://www.w3.org/ns/hydra/error>; rel="http://www.w3.org/ns/json-ld#context" { "type" : "https://api.example.com/vocab#NullReferenceException" , "@type" : "http://www.w3.org/ns/hydra/core#Error" , "title" : "The request cannot be processed." , "detail" : "Provided value cannot be 'null'." , "instance" : "http://api.example.com/api/posts" , "status" : 404 }
6.6. hydra:HeaderSpecification
+| Name: + | HeaderSpecification + |
|---|---|
| Summary: + | Specifies a possible either expected or returned header values. + |
| Sub-class of: + | Resource + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api?documentation" , "@type" : "ApiDocumentation" , "entrypoint" : "http://api.example.com/api" , "extension" : "https://w3id.org/hydra/extension#shacl" , "supportedClass" : [ { "@id" : "http://api.example.com/vocab#User" , "title" : "User" , "description" : "Describes a system user." , "supportedOperation" : [ { "method" : "PUT" , "title" : "Create new user" , "description" : "Creates a brand new user." , "expects" : "http://api.example.com/vocab#User" , "returns" : "http://api.example.com/vocab#User" , "returnsHeader" : [ { "@type" : "hydra:HeaderSpecification" , "headerName" : "Content-Type" , "possibleValue" : [ "text/turtle" , "application/ld+json" ], "closedSet" : true } "Content-Length" ], "expectsHeader" : [ "Authorization" , { "@type" : "hydra:HeaderSpecification" , "headerName" : "Content-Type" , "possibleValue" : [ "image/gif" , "image/png" ], "closedSet" : true } ] } ], "supportedProperty" : [ { "property" : "http://api.example.com/vocab#login" , "writable" : true , "readable" : true , "required" : true } ] } ] }
6.7. hydra:IriTemplate
+| Name: + | IriTemplate + |
|---|---|
| Summary: + | The class of IRI templates. + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api/posts" , "@type" : "Collection" , "view" : { "@id" : "http://api.example.com/api/posts?skip=10" , "@type" : "PartialCollectionView" , "first" : "http://api.example.com/api/posts" , "last" : "http://api.example.com/api/posts?skip=100" , "previous" : "http://api.example.com/api/posts" , "next" : "http://api.example.com/api/posts?skip=20" , "totalItems" : 10 , }, "totalItems" : 100 , "member" : [ { "@id" : "http://api.example.com/api/posts/10" }, { "@id" : "http://api.example.com/api/posts/11" }, { "@id" : "http://api.example.com/api/posts/12" }, { "@id" : "http://api.example.com/api/posts/13" }, { "@id" : "http://api.example.com/api/posts/14" }, { "@id" : "http://api.example.com/api/posts/15" }, { "@id" : "http://api.example.com/api/posts/16" }, { "@id" : "http://api.example.com/api/posts/17" }, { "@id" : "http://api.example.com/api/posts/18" }, { "@id" : "http://api.example.com/api/posts/19" } ], "search" : { "@type" : "hydra:IriTemplate" , "template" : "/api/posts{?search,limit,offset}" , "resolveRelativeUsing" : "hydra:Rfc3986" , "mapping" : [ { "variable" : "search" , "property" : "hydra:freetextQuery" , "required" : true , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "limit" , "property" : "hydra:limit" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "offset" , "property" : "hydra:offset" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" } ] } }
6.8. hydra:IriTemplateMapping
+| Name: + | IriTemplateMapping + |
|---|---|
| Summary: + | A mapping from an IRI template variable to a property. + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api/posts" , "@type" : "Collection" , "view" : { "@id" : "http://api.example.com/api/posts?skip=10" , "@type" : "PartialCollectionView" , "first" : "http://api.example.com/api/posts" , "last" : "http://api.example.com/api/posts?skip=100" , "previous" : "http://api.example.com/api/posts" , "next" : "http://api.example.com/api/posts?skip=20" , "totalItems" : 10 , }, "totalItems" : 100 , "member" : [ { "@id" : "http://api.example.com/api/posts/10" }, { "@id" : "http://api.example.com/api/posts/11" }, { "@id" : "http://api.example.com/api/posts/12" }, { "@id" : "http://api.example.com/api/posts/13" }, { "@id" : "http://api.example.com/api/posts/14" }, { "@id" : "http://api.example.com/api/posts/15" }, { "@id" : "http://api.example.com/api/posts/16" }, { "@id" : "http://api.example.com/api/posts/17" }, { "@id" : "http://api.example.com/api/posts/18" }, { "@id" : "http://api.example.com/api/posts/19" } ], "search" : { "@type" : "hydra:IriTemplate" , "template" : "/api/posts{?search,limit,offset}" , "resolveRelativeUsing" : "hydra:Rfc3986" , "mapping" : [ { "@type" : "hydra:IriTemplateMapping" , "variable" : "search" , "property" : "hydra:freetextQuery" , "required" : true , "variableRepresentation" : "hydra:BasicRepresentation" }, { "@type" : "hydra:IriTemplateMapping" , "variable" : "limit" , "property" : "hydra:limit" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" }, { "@type" : "hydra:IriTemplateMapping" , "variable" : "offset" , "property" : "hydra:offset" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" } ] } }
6.9. hydra:Link
+| Name: + | Link + |
|---|---|
| Summary: + | The class of properties representing links. + |
| Sub-class of: + | Resource, rdf:Property
+ |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@graph" : [ { "@id" : "http://api.example.com/api?documentation" , "@type" : "ApiDocumentation" , "entrypoint" : "http://api.example.com/api" }, { "@id" : "http://api.example.com/vocab#comments" , "@type" : "hydra:Link" } } }
6.10. hydra:Operation
+| Name: + | Operation + |
|---|---|
| Summary: + | An operation. + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api/posts/1" , "operation" : [ { "@type" : "Operation" , "method" : "DELETE" , "title" : "Remove" , "description" : "Removes post no. 1" } ] }
6.11. hydra:PartialCollectionView
+| Name: + | PartialCollectionView + |
|---|---|
| Summary: + | A PartialCollectionView describes a partial view of a Collection. + Multiple PartialCollectionViews can be connected with + the next/previous properties to allow a client to retrieve + all members of the collection. + |
| Sub-class of: + | Resource + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api/posts" , "@type" : "Collection" , "view" : { "@type" : "PartialCollectionView" , "@id" : "http://api.example.com/api/posts?skip=10" , "@type" : "PartialCollectionView" , "first" : "http://api.example.com/api/posts" , "last" : "http://api.example.com/api/posts?skip=100" , "previous" : "http://api.example.com/api/posts" , "next" : "http://api.example.com/api/posts?skip=20" , "totalItems" : 10 , }, "totalItems" : 100 , "member" : [ { "@id" : "http://api.example.com/api/posts/10" }, { "@id" : "http://api.example.com/api/posts/11" }, { "@id" : "http://api.example.com/api/posts/12" }, { "@id" : "http://api.example.com/api/posts/13" }, { "@id" : "http://api.example.com/api/posts/14" }, { "@id" : "http://api.example.com/api/posts/15" }, { "@id" : "http://api.example.com/api/posts/16" }, { "@id" : "http://api.example.com/api/posts/17" }, { "@id" : "http://api.example.com/api/posts/18" }, { "@id" : "http://api.example.com/api/posts/19" } ], "search" : { "template" : "/api/posts{?search,limit,offset}" , "resolveRelativeUsing" : "hydra:Rfc3986" , "mapping" : [ { "variable" : "search" , "property" : "hydra:freetextQuery" , "required" : true , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "limit" , "property" : "hydra:limit" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "offset" , "property" : "hydra:offset" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" } ] } }
6.12. hydra:Resource
+| Name: + | Resource + |
|---|---|
| Summary: + | The class of dereferenceable resources by means a client + can attempt to dereference; however, the received responses + should still be verified. + |
6.13. hydra:RetractedOperationSpecification
+| Name: + | RetractedOperationSpecification + |
|---|---|
| Summary: + | Describes which and why an operation is retracted. + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/doc/" , "@type" : "Collection" , "retractedOperation" : [ { "@type" : "Operation" , "method" : "POST" , "expects" : "http://api.example.com/doc/#Upload" , "reason" : "Unavailable" } ] }
6.14. hydra:Status
+| Name: + | Status + |
|---|---|
| Summary: + | Additional information about a status code that might be returned. + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api/posts/1" , "operation" : [ { "method" : "DELETE" , "title" : "Remove" , "description" : "Removes post no. 1" , "possibleStatus" : [ { "@type" : "Status" , "statusCode" : 303 } ] } ] }
6.15. hydra:SupportedProperty
+| Name: + | SupportedProperty + |
|---|---|
| Summary: + | A property known to be supported by a Hydra class. + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api?documentation" , "@type" : "ApiDocumentation" , "entrypoint" : "http://api.example.com/api" , "extension" : "https://w3id.org/hydra/extension#shacl" , "supportedClass" : [ { "@id" : "http://api.example.com/vocab#User" , "title" : "User" , "description" : "Describes a system user." , "supportedOperation" : [ { "method" : "PUT" , "title" : "Create new user" , "description" : "Creates a brand new user." , "expects" : "http://api.example.com/vocab#User" , "returns" : "http://api.example.com/vocab#User" , "returnsHeader" : [ { "headerName" : "Content-Type" , "possibleValue" : [ "text/turtle" , "application/ld+json" ], "closedSet" : true } "Content-Length" ], "expectsHeader" : [ "Authorization" , { "headerName" : "Content-Type" , "possibleValue" : [ "image/gif" , "image/png" ], "closedSet" : true } ] } ], "supportedProperty" : [ { "@type" : "SupportedProperty" , "property" : "http://api.example.com/vocab#login" , "writable" : true , "readable" : true , "required" : true } ] } ] }
6.16. hydra:TemplatedLink
+| Name: + | TemplatedLink + |
|---|---|
| Summary: + | A templated link. + |
| Sub-class of: + | Resource, rdf:Property
+ |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@graph" : [ { "@id" : "http://api.example.com/api?documentation" , "@type" : "ApiDocumentation" , "entrypoint" : "http://api.example.com/api" }, { "@id" : "http://api.example.com/vocab#comments" , "@type" : "hydra:TemplatedLink" } } }
6.17. hydra:VariableRepresentation
+| Name: + | VariableRepresentation + |
|---|---|
| Summary: + | A representation specifies how to serialize variable + values into strings. + |
| Named instances: + | BasicRepresentation, ExplicitRepresentation + |
6.18. hydra:UnavailabilityReason
+| Name: + | UnavailabilityReason + |
|---|---|
| Summary: + | Provides reasons why the operation cannot be invoked. + |
| Named instances: + | Unavailable, Unauthorized + |
7. Properties
+7.1. hydra:apiDocumentation
+| Name: + | apiDocumentation + |
|---|---|
| Summary: + | A link to the API documentation. + |
| Domain: + | Resource + |
| Range: + | ApiDocumentation + |
+HTTP / 1.1 200 OK Content-Type : text/html; charset=utf-8 Link : <http://api.example.com/doc/>; rel="http://www.w3.org/ns/hydra/core#apiDocumentation"
7.2. hydra:closedSet
+| Name: + | closedSet + |
|---|---|
| Summary: + | Determines whether the provided set of header values + is closed or not. + |
| Max cardinality: + | 1 + |
| Domain: + | HeaderSpecification + |
| Range: + | xsd:boolean
+ |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api?documentation" , "@type" : "ApiDocumentation" , "entrypoint" : "http://api.example.com/api" , "extension" : "https://w3id.org/hydra/extension#shacl" , "supportedClass" : [ { "@id" : "http://api.example.com/vocab#User" , "title" : "User" , "description" : "Describes a system user." , "supportedOperation" : [ { "method" : "PUT" , "title" : "Create new user" , "description" : "Creates a brand new user." , "expects" : "http://api.example.com/vocab#User" , "returns" : "http://api.example.com/vocab#User" , "returnsHeader" : [ { "headerName" : "Content-Type" , "possibleValue" : [ "text/turtle" , "application/ld+json" ], "closedSet" : true } "Content-Length" ], "expectsHeader" : [ "Authorization" , { "headerName" : "Content-Type" , "possibleValue" : [ "image/gif" , "image/png" ], "closedSet" : true } ] } ], "supportedProperty" : [ { "property" : "http://api.example.com/vocab#login" , "writable" : true , "readable" : true , "required" : true } ] } ] }
7.3. hydra:collection
+| Name: + | collection + |
|---|---|
| Summary: + | Collections somehow related to this resource. + |
| Range: + | Collection + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api" , "collection" : [ { "@id" : "http://api.example.com/api/posts" , "@type" : "Collection" , "memberAssertion" : [ { "property" : "rdf:type" , "object" : "http://api.example.com/vocab#Post" } ] } ] }
7.4. hydra:description
+| Name: + | description + |
|---|---|
| Summary: + | A description. + |
| Max cardinality: + | 1 + |
| Domain includes: + | ApiDocumentation, Status, Class, SupportedProperty, Operation, Link, TemplatedLink + |
| Range: + | xsd:string
+ |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api?documentation" , "@type" : "ApiDocumentation" , "entrypoint" : "http://api.example.com/api" , "extension" : "https://w3id.org/hydra/extension#shacl" , "supportedClass" : [ { "@id" : "http://api.example.com/vocab#User" , "title" : "User" , "description" : "Describes a system user." , "supportedOperation" : [ { "method" : "PUT" , "title" : "Create new user" , "description" : "Creates a brand new user." , "expects" : "http://api.example.com/vocab#User" , "returns" : "http://api.example.com/vocab#User" , "returnsHeader" : [ { "headerName" : "Content-Type" , "possibleValue" : [ "text/turtle" , "application/ld+json" ], "closedSet" : true } "Content-Length" ], "expectsHeader" : [ "Authorization" , { "headerName" : "Content-Type" , "possibleValue" : [ "image/gif" , "image/png" ], "closedSet" : true } ] } ], "supportedProperty" : [ { "property" : "http://api.example.com/vocab#login" , "writable" : true , "readable" : true , "required" : true } ] } ] }
7.5. hydra:entrypoint
+| Name: + | entrypoint + |
|---|---|
| Summary: + | A link to main entry point of the Web API. + |
| Min cardinality: + | 1 + |
| Domain: + | ApiDocumentation + |
| Range: + | Resource + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api?documentation" , "@type" : "ApiDocumentation" , "entrypoint" : "http://api.example.com/api" , "extension" : "https://w3id.org/hydra/extension#shacl" , "supportedClass" : [ { "@id" : "http://api.example.com/vocab#User" , "title" : "User" , "description" : "Describes a system user." , "supportedOperation" : [ { "method" : "PUT" , "title" : "Create new user" , "description" : "Creates a brand new user." , "expects" : "http://api.example.com/vocab#User" , "returns" : "http://api.example.com/vocab#User" , "returnsHeader" : [ { "headerName" : "Content-Type" , "possibleValue" : [ "text/turtle" , "application/ld+json" ], "closedSet" : true } "Content-Length" ], "expectsHeader" : [ "Authorization" , { "headerName" : "Content-Type" , "possibleValue" : [ "image/gif" , "image/png" ], "closedSet" : true } ] } ], "supportedProperty" : [ { "property" : "http://api.example.com/vocab#login" , "writable" : true , "readable" : true , "required" : true } ] } ] }
7.6. hydra:expects
+| Name: + | expects + |
|---|---|
| Summary: + | The information expected by the Web API. + |
| Domain includes: + | Operation, RetractedOperationSpecification + |
| Range includes: + | rdfs:Resource, Resource, rdfs:Class, Class
+ |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api?documentation" , "@type" : "ApiDocumentation" , "entrypoint" : "http://api.example.com/api" , "extension" : "https://w3id.org/hydra/extension#shacl" , "supportedClass" : [ { "@id" : "http://api.example.com/vocab#User" , "title" : "User" , "description" : "Describes a system user." , "supportedOperation" : [ { "method" : "PUT" , "title" : "Create new user" , "description" : "Creates a brand new user." , "expects" : "http://api.example.com/vocab#User" , "returns" : "http://api.example.com/vocab#User" , "returnsHeader" : [ { "headerName" : "Content-Type" , "possibleValue" : [ "text/turtle" , "application/ld+json" ], "closedSet" : true } "Content-Length" ], "expectsHeader" : [ "Authorization" , { "headerName" : "Content-Type" , "possibleValue" : [ "image/gif" , "image/png" ], "closedSet" : true } ] } ], "supportedProperty" : [ { "property" : "http://api.example.com/vocab#login" , "writable" : true , "readable" : true , "required" : true } ] } ] }
7.7. hydra:expectsHeader
+| Name: + | expectsHeader + |
|---|---|
| Summary: + | Specification of the header expected by the operation. + |
| Domain: + | Operation + |
| Range includes: + | xsd:string, HeaderSpecification
+ |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api?documentation" , "@type" : "ApiDocumentation" , "entrypoint" : "http://api.example.com/api" , "extension" : "https://w3id.org/hydra/extension#shacl" , "supportedClass" : [ { "@id" : "http://api.example.com/vocab#User" , "title" : "User" , "description" : "Describes a system user." , "supportedOperation" : [ { "method" : "PUT" , "title" : "Create new user" , "description" : "Creates a brand new user." , "expects" : "http://api.example.com/vocab#User" , "returns" : "http://api.example.com/vocab#User" , "returnsHeader" : [ { "headerName" : "Content-Type" , "possibleValue" : [ "text/turtle" , "application/ld+json" ], "closedSet" : true } "Content-Length" ], "expectsHeader" : [ "Authorization" , { "headerName" : "Content-Type" , "possibleValue" : [ "image/gif" , "image/png" ], "closedSet" : true } ] } ], "supportedProperty" : [ { "property" : "http://api.example.com/vocab#login" , "writable" : true , "readable" : true , "required" : true } ] } ] }
7.8. hydra:extension
+| Name: + | extension + |
|---|---|
| Summary: + | Hint on what kind of extensions are in use. + |
| Domain: + | ApiDocumentation + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api?documentation" , "@type" : "ApiDocumentation" , "entrypoint" : "http://api.example.com/api" , "extension" : "https://w3id.org/hydra/extension#shacl" , "supportedClass" : [ { "@id" : "http://api.example.com/vocab#User" , "title" : "User" , "description" : "Describes a system user." , "supportedOperation" : [ { "method" : "PUT" , "title" : "Create new user" , "description" : "Creates a brand new user." , "expects" : "http://api.example.com/vocab#User" , "returns" : "http://api.example.com/vocab#User" , "returnsHeader" : [ { "headerName" : "Content-Type" , "possibleValue" : [ "text/turtle" , "application/ld+json" ], "closedSet" : true } "Content-Length" ], "expectsHeader" : [ "Authorization" , { "headerName" : "Content-Type" , "possibleValue" : [ "image/gif" , "image/png" ], "closedSet" : true } ] } ], "supportedProperty" : [ { "property" : "http://api.example.com/vocab#login" , "writable" : true , "readable" : true , "required" : true } ] } ] }
7.9. hydra:first
+| Name: + | first + |
|---|---|
| Summary: + | The first resource of an interlinked set of resources. + |
| Max cardinality: + | 1 + |
| Domain: + | Resource + |
| Range: + | Resource + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api/posts" , "@type" : "Collection" , "view" : { "@id" : "http://api.example.com/api/posts?skip=10" , "@type" : "PartialCollectionView" , "first" : "http://api.example.com/api/posts" , "last" : "http://api.example.com/api/posts?skip=100" , "previous" : "http://api.example.com/api/posts" , "next" : "http://api.example.com/api/posts?skip=20" , "totalItems" : 10 , }, "totalItems" : 100 , "member" : [ { "@id" : "http://api.example.com/api/posts/10" }, { "@id" : "http://api.example.com/api/posts/11" }, { "@id" : "http://api.example.com/api/posts/12" }, { "@id" : "http://api.example.com/api/posts/13" }, { "@id" : "http://api.example.com/api/posts/14" }, { "@id" : "http://api.example.com/api/posts/15" }, { "@id" : "http://api.example.com/api/posts/16" }, { "@id" : "http://api.example.com/api/posts/17" }, { "@id" : "http://api.example.com/api/posts/18" }, { "@id" : "http://api.example.com/api/posts/19" } ], "search" : { "template" : "/api/posts{?search,limit,offset}" , "resolveRelativeUsing" : "hydra:Rfc3986" , "mapping" : [ { "variable" : "search" , "property" : "hydra:freetextQuery" , "required" : true , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "limit" , "property" : "hydra:limit" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "offset" , "property" : "hydra:offset" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" } ] } }
7.10. hydra:freetextQuery
+| Name: + | freetextQuery + |
|---|---|
| Summary: + | A property representing a freetext query. + |
| Domain: + | Resource + |
| Range: + | xsd:string
+ |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api/posts" , "@type" : "Collection" , "view" : { "@id" : "http://api.example.com/api/posts?skip=10" , "@type" : "PartialCollectionView" , "first" : "http://api.example.com/api/posts" , "last" : "http://api.example.com/api/posts?skip=100" , "previous" : "http://api.example.com/api/posts" , "next" : "http://api.example.com/api/posts?skip=20" , "totalItems" : 10 , }, "totalItems" : 100 , "member" : [ { "@id" : "http://api.example.com/api/posts/10" }, { "@id" : "http://api.example.com/api/posts/11" }, { "@id" : "http://api.example.com/api/posts/12" }, { "@id" : "http://api.example.com/api/posts/13" }, { "@id" : "http://api.example.com/api/posts/14" }, { "@id" : "http://api.example.com/api/posts/15" }, { "@id" : "http://api.example.com/api/posts/16" }, { "@id" : "http://api.example.com/api/posts/17" }, { "@id" : "http://api.example.com/api/posts/18" }, { "@id" : "http://api.example.com/api/posts/19" } ], "search" : { "template" : "/api/posts{?search,limit,offset}" , "resolveRelativeUsing" : "hydra:Rfc3986" , "mapping" : [ { "variable" : "search" , "property" : "hydra:freetextQuery" , "required" : true , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "limit" , "property" : "hydra:limit" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "offset" , "property" : "hydra:offset" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" } ] } }
7.11. hydra:headerName
+| Name: + | headerName + |
|---|---|
| Summary: + | Name of the header. + |
| Min cardinality: + | 1 + |
| Max cardinality: + | 1 + |
| Domain: + | HeaderSpecification + |
| Range: + | xsd:string
+ |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api?documentation" , "@type" : "ApiDocumentation" , "entrypoint" : "http://api.example.com/api" , "extension" : "https://w3id.org/hydra/extension#shacl" , "supportedClass" : [ { "@id" : "http://api.example.com/vocab#User" , "title" : "User" , "description" : "Describes a system user." , "supportedOperation" : [ { "method" : "PUT" , "title" : "Create new user" , "description" : "Creates a brand new user." , "expects" : "http://api.example.com/vocab#User" , "returns" : "http://api.example.com/vocab#User" , "returnsHeader" : [ { "headerName" : "Content-Type" , "possibleValue" : [ "text/turtle" , "application/ld+json" ], "closedSet" : true } "Content-Length" ], "expectsHeader" : [ "Authorization" , { "headerName" : "Content-Type" , "possibleValue" : [ "image/gif" , "image/png" ], "closedSet" : true } ] } ], "supportedProperty" : [ { "property" : "http://api.example.com/vocab#login" , "writable" : true , "readable" : true , "required" : true } ] } ] }
7.12. hydra:last
+| Name: + | last + |
|---|---|
| Summary: + | The last resource of an interlinked set of resources. + |
| Max cardinality: + | 1 + |
| Domain: + | Resource + |
| Range: + | Resource + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api/posts" , "@type" : "Collection" , "view" : { "@id" : "http://api.example.com/api/posts?skip=10" , "@type" : "PartialCollectionView" , "first" : "http://api.example.com/api/posts" , "last" : "http://api.example.com/api/posts?skip=100" , "previous" : "http://api.example.com/api/posts" , "next" : "http://api.example.com/api/posts?skip=20" , "totalItems" : 10 , }, "totalItems" : 100 , "member" : [ { "@id" : "http://api.example.com/api/posts/10" }, { "@id" : "http://api.example.com/api/posts/11" }, { "@id" : "http://api.example.com/api/posts/12" }, { "@id" : "http://api.example.com/api/posts/13" }, { "@id" : "http://api.example.com/api/posts/14" }, { "@id" : "http://api.example.com/api/posts/15" }, { "@id" : "http://api.example.com/api/posts/16" }, { "@id" : "http://api.example.com/api/posts/17" }, { "@id" : "http://api.example.com/api/posts/18" }, { "@id" : "http://api.example.com/api/posts/19" } ], "search" : { "template" : "/api/posts{?search,limit,offset}" , "resolveRelativeUsing" : "hydra:Rfc3986" , "mapping" : [ { "variable" : "search" , "property" : "hydra:freetextQuery" , "required" : true , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "limit" , "property" : "hydra:limit" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "offset" , "property" : "hydra:offset" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" } ] } }
7.13. hydra:limit
+| Name: + | limit + |
|---|---|
| Summary: + | Instructs to limit set only to N elements. + |
| Max cardinality: + | 1 + |
| Range: + | xsd:nonNegativeInteger
+ |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api/posts" , "@type" : "Collection" , "view" : { "@id" : "http://api.example.com/api/posts?skip=10" , "@type" : "PartialCollectionView" , "first" : "http://api.example.com/api/posts" , "last" : "http://api.example.com/api/posts?skip=100" , "previous" : "http://api.example.com/api/posts" , "next" : "http://api.example.com/api/posts?skip=20" , "totalItems" : 10 , }, "totalItems" : 100 , "member" : [ { "@id" : "http://api.example.com/api/posts/10" }, { "@id" : "http://api.example.com/api/posts/11" }, { "@id" : "http://api.example.com/api/posts/12" }, { "@id" : "http://api.example.com/api/posts/13" }, { "@id" : "http://api.example.com/api/posts/14" }, { "@id" : "http://api.example.com/api/posts/15" }, { "@id" : "http://api.example.com/api/posts/16" }, { "@id" : "http://api.example.com/api/posts/17" }, { "@id" : "http://api.example.com/api/posts/18" }, { "@id" : "http://api.example.com/api/posts/19" } ], "search" : { "template" : "/api/posts{?search,limit,offset}" , "resolveRelativeUsing" : "hydra:Rfc3986" , "mapping" : [ { "variable" : "search" , "property" : "hydra:freetextQuery" , "required" : true , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "limit" , "property" : "hydra:limit" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "offset" , "property" : "hydra:offset" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" } ] } }
7.14. hydra:mapping
+| Name: + | mapping + |
|---|---|
| Summary: + | A variable-to-property mapping of the IRI template. + |
| Min cardinality: + | 1 + |
| Domain: + | IriTemplate + |
| Range: + | IriTemplateMapping + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api/posts" , "@type" : "Collection" , "view" : { "@id" : "http://api.example.com/api/posts?skip=10" , "@type" : "PartialCollectionView" , "first" : "http://api.example.com/api/posts" , "last" : "http://api.example.com/api/posts?skip=100" , "previous" : "http://api.example.com/api/posts" , "next" : "http://api.example.com/api/posts?skip=20" , "totalItems" : 10 , }, "totalItems" : 100 , "member" : [ { "@id" : "http://api.example.com/api/posts/10" }, { "@id" : "http://api.example.com/api/posts/11" }, { "@id" : "http://api.example.com/api/posts/12" }, { "@id" : "http://api.example.com/api/posts/13" }, { "@id" : "http://api.example.com/api/posts/14" }, { "@id" : "http://api.example.com/api/posts/15" }, { "@id" : "http://api.example.com/api/posts/16" }, { "@id" : "http://api.example.com/api/posts/17" }, { "@id" : "http://api.example.com/api/posts/18" }, { "@id" : "http://api.example.com/api/posts/19" } ], "search" : { "template" : "/api/posts{?search,limit,offset}" , "resolveRelativeUsing" : "hydra:Rfc3986" , "mapping" : [ { "variable" : "search" , "property" : "hydra:freetextQuery" , "required" : true , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "limit" , "property" : "hydra:limit" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "offset" , "property" : "hydra:offset" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" } ] } }
7.15. hydra:member
+| Name: + | member + |
|---|---|
| Summary: + | A member of the collection. + |
| Domain: + | Collection + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api/posts" , "@type" : "Collection" , "view" : { "@id" : "http://api.example.com/api/posts?skip=10" , "@type" : "PartialCollectionView" , "first" : "http://api.example.com/api/posts" , "last" : "http://api.example.com/api/posts?skip=100" , "previous" : "http://api.example.com/api/posts" , "next" : "http://api.example.com/api/posts?skip=20" , "totalItems" : 10 , }, "totalItems" : 100 , "member" : [ { "@id" : "http://api.example.com/api/posts/10" }, { "@id" : "http://api.example.com/api/posts/11" }, { "@id" : "http://api.example.com/api/posts/12" }, { "@id" : "http://api.example.com/api/posts/13" }, { "@id" : "http://api.example.com/api/posts/14" }, { "@id" : "http://api.example.com/api/posts/15" }, { "@id" : "http://api.example.com/api/posts/16" }, { "@id" : "http://api.example.com/api/posts/17" }, { "@id" : "http://api.example.com/api/posts/18" }, { "@id" : "http://api.example.com/api/posts/19" } ], "search" : { "template" : "/api/posts{?search,limit,offset}" , "resolveRelativeUsing" : "hydra:Rfc3986" , "mapping" : [ { "variable" : "search" , "property" : "hydra:freetextQuery" , "required" : true , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "limit" , "property" : "hydra:limit" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "offset" , "property" : "hydra:offset" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" } ] } }
7.16. hydra:memberAssertion
+| Name: + | memberAssertion + |
|---|---|
| Summary: + | Semantics of each member provided by the collection. + |
| Domain includes: + | Collection, Class + |
| Range: + | + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api" , "collection" : [ { "@id" : "http://api.example.com/api/posts" , "@type" : "Collection" , "memberAssertion" : [ { "property" : "rdf:type" , "object" : "http://api.example.com/vocab#Post" } ] } ] }
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api/posts/1/comments" , "@type" : "Collection" , "memberAssertion" : [ { "subject" : "http://api.example.com/api/posts/1" , "property" : "http://api.example.com/vocab#comment" } ] }
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@graph" : [ { "@id" : "http://api.example.com/api?documentation" , "@type" : "ApiDocumentation" , "entrypoint" : "http://api.example.com/api" }, { "@id" : "http://api.example.com/vocab#comments" , "@type" : "hydra:Link" , "supportedOperation" : [ { "method" : "GET" , "returns" : { "subClassOf" : "hydra:Collection" , "memberAssertion" : { "property" : "rdf:type" , "object" : "http://api.example.com/vocab#Comment" } } } ] } } }
7.17. hydra:method
+| Name: + | method + |
|---|---|
| Summary: + | The protocol method. + |
| Domain includes: + | Operation, RetractedOperationSpecification + |
| Range: + | xsd:string
+ |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api?documentation" , "@type" : "ApiDocumentation" , "entrypoint" : "http://api.example.com/api" , "extension" : "https://w3id.org/hydra/extension#shacl" , "supportedClass" : [ { "@id" : "http://api.example.com/vocab#User" , "title" : "User" , "description" : "Describes a system user." , "supportedOperation" : [ { "method" : "PUT" , "title" : "Create new user" , "description" : "Creates a brand new user." , "expects" : "http://api.example.com/vocab#User" , "returns" : "http://api.example.com/vocab#User" , "returnsHeader" : [ { "headerName" : "Content-Type" , "possibleValue" : [ "text/turtle" , "application/ld+json" ], "closedSet" : true } "Content-Length" ], "expectsHeader" : [ "Authorization" , { "headerName" : "Content-Type" , "possibleValue" : [ "image/gif" , "image/png" ], "closedSet" : true } ] } ], "supportedProperty" : [ { "property" : "http://api.example.com/vocab#login" , "writable" : true , "readable" : true , "required" : true } ] } ] }
7.18. hydra:next
+| Name: + | next + |
|---|---|
| Summary: + | The resource following the current instance + in an interlinked set of resources. + |
| Max cardinality: + | 1 + |
| Domain: + | Resource + |
| Range: + | Resource + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api/posts" , "@type" : "Collection" , "view" : { "@id" : "http://api.example.com/api/posts?skip=10" , "@type" : "PartialCollectionView" , "first" : "http://api.example.com/api/posts" , "last" : "http://api.example.com/api/posts?skip=100" , "previous" : "http://api.example.com/api/posts" , "next" : "http://api.example.com/api/posts?skip=20" , "totalItems" : 10 , }, "totalItems" : 100 , "member" : [ { "@id" : "http://api.example.com/api/posts/10" }, { "@id" : "http://api.example.com/api/posts/11" }, { "@id" : "http://api.example.com/api/posts/12" }, { "@id" : "http://api.example.com/api/posts/13" }, { "@id" : "http://api.example.com/api/posts/14" }, { "@id" : "http://api.example.com/api/posts/15" }, { "@id" : "http://api.example.com/api/posts/16" }, { "@id" : "http://api.example.com/api/posts/17" }, { "@id" : "http://api.example.com/api/posts/18" }, { "@id" : "http://api.example.com/api/posts/19" } ], "search" : { "template" : "/api/posts{?search,limit,offset}" , "resolveRelativeUsing" : "hydra:Rfc3986" , "mapping" : [ { "variable" : "search" , "property" : "hydra:freetextQuery" , "required" : true , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "limit" , "property" : "hydra:limit" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "offset" , "property" : "hydra:offset" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" } ] } }
7.19. hydra:object
+| Name: + | object + |
|---|---|
| Summary: + | The object. + |
| Min cardinality: + | 1 + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api" , "collection" : [ { "@id" : "http://api.example.com/api/posts" , "@type" : "Collection" , "memberAssertion" : [ { "property" : "rdf:type" , "object" : "http://api.example.com/vocab#Post" } ] } ] }
7.20. hydra:offset
+| Name: + | offset + |
|---|---|
| Summary: + | Instructs to skip N elements of the set. + |
| Max cardinality: + | 1 + |
| Range: + | xsd:nonNegativeInteger
+ |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api/posts" , "@type" : "Collection" , "view" : { "@id" : "http://api.example.com/api/posts?skip=10" , "@type" : "PartialCollectionView" , "first" : "http://api.example.com/api/posts" , "last" : "http://api.example.com/api/posts?skip=100" , "previous" : "http://api.example.com/api/posts" , "next" : "http://api.example.com/api/posts?skip=20" , "totalItems" : 10 , }, "totalItems" : 100 , "member" : [ { "@id" : "http://api.example.com/api/posts/10" }, { "@id" : "http://api.example.com/api/posts/11" }, { "@id" : "http://api.example.com/api/posts/12" }, { "@id" : "http://api.example.com/api/posts/13" }, { "@id" : "http://api.example.com/api/posts/14" }, { "@id" : "http://api.example.com/api/posts/15" }, { "@id" : "http://api.example.com/api/posts/16" }, { "@id" : "http://api.example.com/api/posts/17" }, { "@id" : "http://api.example.com/api/posts/18" }, { "@id" : "http://api.example.com/api/posts/19" } ], "search" : { "template" : "/api/posts{?search,limit,offset}" , "resolveRelativeUsing" : "hydra:Rfc3986" , "mapping" : [ { "variable" : "search" , "property" : "hydra:freetextQuery" , "required" : true , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "limit" , "property" : "hydra:limit" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "offset" , "property" : "hydra:offset" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" } ] } }
7.21. hydra:operation
+| Name: + | operation + |
|---|---|
| Summary: + | An operation supported by the Hydra resource. + |
| Domain: + | Resource + |
| Range: + | Operation + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api/posts/1" , "operation" : [ { "method" : "DELETE" , "title" : "Remove" , "description" : "Removes post no. 1" } ] }
7.22. hydra:pageIndex
+| Name: + | pageIndex + |
|---|---|
| Summary: + | Instructs to provide a specific page of the collection + at a given index. + |
| Max cardinality: + | 1 + |
| Range: + | xsd:nonNegativeInteger
+ |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api/posts" , "@type" : "Collection" , "view" : { "@id" : "http://api.example.com/api/posts?skip=10" , "@type" : "PartialCollectionView" , "first" : "http://api.example.com/api/posts" , "last" : "http://api.example.com/api/posts?skip=100" , "previous" : "http://api.example.com/api/posts" , "next" : "http://api.example.com/api/posts?skip=20" , "totalItems" : 10 , }, "totalItems" : 100 , "member" : [ { "@id" : "http://api.example.com/api/posts/10" }, { "@id" : "http://api.example.com/api/posts/11" }, { "@id" : "http://api.example.com/api/posts/12" }, { "@id" : "http://api.example.com/api/posts/13" }, { "@id" : "http://api.example.com/api/posts/14" }, { "@id" : "http://api.example.com/api/posts/15" }, { "@id" : "http://api.example.com/api/posts/16" }, { "@id" : "http://api.example.com/api/posts/17" }, { "@id" : "http://api.example.com/api/posts/18" }, { "@id" : "http://api.example.com/api/posts/19" } ], "search" : { "template" : "/api/posts{?search,page,limit}" , "resolveRelativeUsing" : "hydra:Rfc3986" , "mapping" : [ { "variable" : "search" , "property" : "hydra:freetextQuery" , "required" : true , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "limit" , "property" : "hydra:limit" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "page" , "property" : "hydra:pageIndex" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" } ] } }
7.23. hydra:pageReference
+| Name: + | pageReference + |
|---|---|
| Summary: + | Instructs to provide a specific page reference + of the collection. + |
| Max cardinality: + | 1 + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api/posts" , "@type" : "Collection" , "view" : { "@id" : "http://api.example.com/api/posts?skip=10" , "@type" : "PartialCollectionView" , "first" : "http://api.example.com/api/posts" , "last" : "http://api.example.com/api/posts?skip=100" , "previous" : "http://api.example.com/api/posts" , "next" : "http://api.example.com/api/posts?skip=20" , "totalItems" : 10 , }, "totalItems" : 100 , "member" : [ { "@id" : "http://api.example.com/api/posts/10" }, { "@id" : "http://api.example.com/api/posts/11" }, { "@id" : "http://api.example.com/api/posts/12" }, { "@id" : "http://api.example.com/api/posts/13" }, { "@id" : "http://api.example.com/api/posts/14" }, { "@id" : "http://api.example.com/api/posts/15" }, { "@id" : "http://api.example.com/api/posts/16" }, { "@id" : "http://api.example.com/api/posts/17" }, { "@id" : "http://api.example.com/api/posts/18" }, { "@id" : "http://api.example.com/api/posts/19" } ], "search" : { "template" : "/api/posts{?search,partOfDay,limit}" , "resolveRelativeUsing" : "hydra:Rfc3986" , "mapping" : [ { "variable" : "search" , "property" : "hydra:freetextQuery" , "required" : true , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "limit" , "property" : "hydra:limit" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "partOfDay" , "property" : "hydra:pageReference" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" } ] } }
7.24. hydra:possibleStatus
+| Name: + | possibleStatus + |
|---|---|
| Summary: + | A status that might be returned by the Web API (other + statuses should be expected and properly handled as well). + |
| Domain includes: + | ApiDocumentation, Operation, RetractedOperationSpecification + |
| Range: + | Status + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api/posts/1" , "operation" : [ { "method" : "DELETE" , "title" : "Remove" , "description" : "Removes post no. 1" , "possibleStatus" : [ { "@type" : "Status" , "statusCode" : 303 } ] } ] }
7.25. hydra:possibleValue
+| Name: + | possibleValue + |
|---|---|
| Summary: + | Possible value of the header. + |
| Min cardinality: + | 1 + |
| Domain: + | HeaderSpecification + |
| Range: + | xsd:string
+ |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api?documentation" , "@type" : "ApiDocumentation" , "entrypoint" : "http://api.example.com/api" , "extension" : "https://w3id.org/hydra/extension#shacl" , "supportedClass" : [ { "@id" : "http://api.example.com/vocab#User" , "title" : "User" , "description" : "Describes a system user." , "supportedOperation" : [ { "method" : "PUT" , "title" : "Create new user" , "description" : "Creates a brand new user." , "expects" : "http://api.example.com/vocab#User" , "returns" : "http://api.example.com/vocab#User" , "returnsHeader" : [ { "headerName" : "Content-Type" , "possibleValue" : [ "text/turtle" , "application/ld+json" ], "closedSet" : true } "Content-Length" ], "expectsHeader" : [ "Authorization" , { "headerName" : "Content-Type" , "possibleValue" : [ "image/gif" , "image/png" ], "closedSet" : true } ] } ], "supportedProperty" : [ { "property" : "http://api.example.com/vocab#login" , "writable" : true , "readable" : true , "required" : true } ] } ] }
7.26. hydra:previous
+| Name: + | previous + |
|---|---|
| Summary: + | The resource preceding the current instance + in an interlinked set of resources. + |
| Max cardinality: + | 1 + |
| Domain: + | Resource + |
| Range: + | Resource + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api/posts" , "@type" : "Collection" , "view" : { "@id" : "http://api.example.com/api/posts?skip=10" , "@type" : "PartialCollectionView" , "first" : "http://api.example.com/api/posts" , "last" : "http://api.example.com/api/posts?skip=100" , "previous" : "http://api.example.com/api/posts" , "next" : "http://api.example.com/api/posts?skip=20" , "totalItems" : 10 , }, "totalItems" : 100 , "member" : [ { "@id" : "http://api.example.com/api/posts/10" }, { "@id" : "http://api.example.com/api/posts/11" }, { "@id" : "http://api.example.com/api/posts/12" }, { "@id" : "http://api.example.com/api/posts/13" }, { "@id" : "http://api.example.com/api/posts/14" }, { "@id" : "http://api.example.com/api/posts/15" }, { "@id" : "http://api.example.com/api/posts/16" }, { "@id" : "http://api.example.com/api/posts/17" }, { "@id" : "http://api.example.com/api/posts/18" }, { "@id" : "http://api.example.com/api/posts/19" } ], "search" : { "template" : "/api/posts{?search,limit,offset}" , "resolveRelativeUsing" : "hydra:Rfc3986" , "mapping" : [ { "variable" : "search" , "property" : "hydra:freetextQuery" , "required" : true , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "limit" , "property" : "hydra:limit" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "offset" , "property" : "hydra:offset" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" } ] } }
7.27. hydra:property
+ (only when used in context of memberAssertion) +| Name: + | property + |
|---|---|
| Summary: + | A property. + |
| Min cardinality: + | 1 + |
| Domain includes: + | SupportedProperty, IriTemplateMapping + |
| Range: + | rdf:Property
+ |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api?documentation" , "@type" : "ApiDocumentation" , "entrypoint" : "http://api.example.com/api" , "extension" : "https://w3id.org/hydra/extension#shacl" , "supportedClass" : [ { "@id" : "http://api.example.com/vocab#User" , "title" : "User" , "description" : "Describes a system user." , "supportedOperation" : [ { "method" : "PUT" , "title" : "Create new user" , "description" : "Creates a brand new user." , "expects" : "http://api.example.com/vocab#User" , "returns" : "http://api.example.com/vocab#User" , "returnsHeader" : [ { "headerName" : "Content-Type" , "possibleValue" : [ "text/turtle" , "application/ld+json" ], "closedSet" : true } "Content-Length" ], "expectsHeader" : [ "Authorization" , { "headerName" : "Content-Type" , "possibleValue" : [ "image/gif" , "image/png" ], "closedSet" : true } ] } ], "supportedProperty" : [ { "property" : "http://api.example.com/vocab#login" , "writable" : true , "readable" : true , "required" : true } ] } ] }
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api/posts" , "@type" : "Collection" , "view" : { "@id" : "http://api.example.com/api/posts?skip=10" , "@type" : "PartialCollectionView" , "first" : "http://api.example.com/api/posts" , "last" : "http://api.example.com/api/posts?skip=100" , "previous" : "http://api.example.com/api/posts" , "next" : "http://api.example.com/api/posts?skip=20" , "totalItems" : 10 , }, "totalItems" : 100 , "member" : [ { "@id" : "http://api.example.com/api/posts/10" }, { "@id" : "http://api.example.com/api/posts/11" }, { "@id" : "http://api.example.com/api/posts/12" }, { "@id" : "http://api.example.com/api/posts/13" }, { "@id" : "http://api.example.com/api/posts/14" }, { "@id" : "http://api.example.com/api/posts/15" }, { "@id" : "http://api.example.com/api/posts/16" }, { "@id" : "http://api.example.com/api/posts/17" }, { "@id" : "http://api.example.com/api/posts/18" }, { "@id" : "http://api.example.com/api/posts/19" } ], "search" : { "template" : "/api/posts{?search,limit,offset}" , "resolveRelativeUsing" : "hydra:Rfc3986" , "mapping" : [ { "variable" : "search" , "property" : "hydra:freetextQuery" , "required" : true , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "limit" , "property" : "hydra:limit" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "offset" , "property" : "hydra:offset" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" } ] } }
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api" , "collection" : [ { "@id" : "http://api.example.com/api/posts" , "@type" : "Collection" , "memberAssertion" : [ { "property" : "rdf:type" , "object" : "http://api.example.com/vocab#Post" } ] } ] }
7.28. hydra:readable
+| Name: + | readable + |
|---|---|
| Summary: + | True if the client can retrieve the property’s value, + false otherwise. + |
| Max cardinality: + | 1 + |
| Domain: + | SupportedProperty + |
| Range: + | xsd:boolean
+ |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api?documentation" , "@type" : "ApiDocumentation" , "entrypoint" : "http://api.example.com/api" , "extension" : "https://w3id.org/hydra/extension#shacl" , "supportedClass" : [ { "@id" : "http://api.example.com/vocab#User" , "title" : "User" , "description" : "Describes a system user." , "supportedOperation" : [ { "method" : "PUT" , "title" : "Create new user" , "description" : "Creates a brand new user." , "expects" : "http://api.example.com/vocab#User" , "returns" : "http://api.example.com/vocab#User" , "returnsHeader" : [ { "headerName" : "Content-Type" , "possibleValue" : [ "text/turtle" , "application/ld+json" ], "closedSet" : true } "Content-Length" ], "expectsHeader" : [ "Authorization" , { "headerName" : "Content-Type" , "possibleValue" : [ "image/gif" , "image/png" ], "closedSet" : true } ] } ], "supportedProperty" : [ { "property" : "http://api.example.com/vocab#login" , "writable" : true , "readable" : true , "required" : true } ] } ] }
7.29. hydra:reason
+| Name: + | reason + |
|---|---|
| Summary: + | Reason of why the operation is retracted. + |
| Max cardinality: + | 1 + |
| Domain: + | RetractedOperationSpecification + |
| Range: + | UnavailabilityReason + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/doc/" , "@type" : "Collection" , "retractedOperation" : [ { "@type" : "Operation" , "method" : "POST" , "expects" : "http://api.example.com/doc/#Upload" , "reason" : "Unavailable" } ] }
7.30. hydra:retractedOperation
+| Name: + | retractedOperation + |
|---|---|
| Summary: + | Retracts available operations. + |
| Domain: + | Resource + |
| Range: + | RetractedOperationSpecification + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/doc/" , "@type" : "Collection" , "retractedOperation" : [ { "@type" : "Operation" , "method" : "POST" , "expects" : "http://api.example.com/doc/#Upload" , "reason" : "Unavailable" } ] }
7.31. hydra:required
+| Name: + | required + |
|---|---|
| Summary: + | True if the property is required, false otherwise. + |
| Max cardinality: + | 1 + |
| Domain includes: + | SupportedProperty, IriTemplateMapping + |
| Range: + | xsd:boolean
+ |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api?documentation" , "@type" : "ApiDocumentation" , "entrypoint" : "http://api.example.com/api" , "extension" : "https://w3id.org/hydra/extension#shacl" , "supportedClass" : [ { "@id" : "http://api.example.com/vocab#User" , "title" : "User" , "description" : "Describes a system user." , "supportedOperation" : [ { "method" : "PUT" , "title" : "Create new user" , "description" : "Creates a brand new user." , "expects" : "http://api.example.com/vocab#User" , "returns" : "http://api.example.com/vocab#User" , "returnsHeader" : [ { "headerName" : "Content-Type" , "possibleValue" : [ "text/turtle" , "application/ld+json" ], "closedSet" : true } "Content-Length" ], "expectsHeader" : [ "Authorization" , { "headerName" : "Content-Type" , "possibleValue" : [ "image/gif" , "image/png" ], "closedSet" : true } ] } ], "supportedProperty" : [ { "property" : "http://api.example.com/vocab#login" , "writable" : true , "readable" : true , "required" : true } ] } ] }
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api/posts" , "@type" : "Collection" , "view" : { "@id" : "http://api.example.com/api/posts?skip=10" , "@type" : "PartialCollectionView" , "first" : "http://api.example.com/api/posts" , "last" : "http://api.example.com/api/posts?skip=100" , "previous" : "http://api.example.com/api/posts" , "next" : "http://api.example.com/api/posts?skip=20" , "totalItems" : 10 , }, "totalItems" : 100 , "member" : [ { "@id" : "http://api.example.com/api/posts/10" }, { "@id" : "http://api.example.com/api/posts/11" }, { "@id" : "http://api.example.com/api/posts/12" }, { "@id" : "http://api.example.com/api/posts/13" }, { "@id" : "http://api.example.com/api/posts/14" }, { "@id" : "http://api.example.com/api/posts/15" }, { "@id" : "http://api.example.com/api/posts/16" }, { "@id" : "http://api.example.com/api/posts/17" }, { "@id" : "http://api.example.com/api/posts/18" }, { "@id" : "http://api.example.com/api/posts/19" } ], "search" : { "template" : "/api/posts{?search,limit,offset}" , "resolveRelativeUsing" : "hydra:Rfc3986" , "mapping" : [ { "variable" : "search" , "property" : "hydra:freetextQuery" , "required" : true , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "limit" , "property" : "hydra:limit" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "offset" , "property" : "hydra:offset" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" } ] } }
7.32. hydra:resolveRelativeUsing
+| Name: + | resolveRelativeUsing + |
|---|---|
| Summary: + | Instructs on how to resolve relative Uri created + by the Iri template resolution. + |
| Max cardinality: + | 1 + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api/posts" , "@type" : "Collection" , "view" : { "@id" : "http://api.example.com/api/posts?skip=10" , "@type" : "PartialCollectionView" , "first" : "http://api.example.com/api/posts" , "last" : "http://api.example.com/api/posts?skip=100" , "previous" : "http://api.example.com/api/posts" , "next" : "http://api.example.com/api/posts?skip=20" , "totalItems" : 10 , }, "totalItems" : 100 , "member" : [ { "@id" : "http://api.example.com/api/posts/10" }, { "@id" : "http://api.example.com/api/posts/11" }, { "@id" : "http://api.example.com/api/posts/12" }, { "@id" : "http://api.example.com/api/posts/13" }, { "@id" : "http://api.example.com/api/posts/14" }, { "@id" : "http://api.example.com/api/posts/15" }, { "@id" : "http://api.example.com/api/posts/16" }, { "@id" : "http://api.example.com/api/posts/17" }, { "@id" : "http://api.example.com/api/posts/18" }, { "@id" : "http://api.example.com/api/posts/19" } ], "search" : { "template" : "/api/posts{?search,limit,offset}" , "resolveRelativeUsing" : "hydra:Rfc3986" , "mapping" : [ { "variable" : "search" , "property" : "hydra:freetextQuery" , "required" : true , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "limit" , "property" : "hydra:limit" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "offset" , "property" : "hydra:offset" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" } ] } }
7.33. hydra:returns
+| Name: + | returns + |
|---|---|
| Summary: + | The information returned by the Web API on success. + |
| Domain includes: + | Operation, RetractedOperationSpecification + |
| Range includes: + | rdfs:Resource, Resource, rdfs:Class, Class
+ |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api?documentation" , "@type" : "ApiDocumentation" , "entrypoint" : "http://api.example.com/api" , "extension" : "https://w3id.org/hydra/extension#shacl" , "supportedClass" : [ { "@id" : "http://api.example.com/vocab#User" , "title" : "User" , "description" : "Describes a system user." , "supportedOperation" : [ { "method" : "PUT" , "title" : "Create new user" , "description" : "Creates a brand new user." , "expects" : "http://api.example.com/vocab#User" , "returns" : "http://api.example.com/vocab#User" , "returnsHeader" : [ { "headerName" : "Content-Type" , "possibleValue" : [ "text/turtle" , "application/ld+json" ], "closedSet" : true } "Content-Length" ], "expectsHeader" : [ "Authorization" , { "headerName" : "Content-Type" , "possibleValue" : [ "image/gif" , "image/png" ], "closedSet" : true } ] } ], "supportedProperty" : [ { "property" : "http://api.example.com/vocab#login" , "writable" : true , "readable" : true , "required" : true } ] } ] }
7.34. hydra:returnsHeader
+| Name: + | returnsHeader + |
|---|---|
| Summary: + | Name of the header returned by the operation. + |
| Domain: + | Operation + |
| Range includes: + | xsd:string, HeaderSpecification
+ |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api?documentation" , "@type" : "ApiDocumentation" , "entrypoint" : "http://api.example.com/api" , "extension" : "https://w3id.org/hydra/extension#shacl" , "supportedClass" : [ { "@id" : "http://api.example.com/vocab#User" , "title" : "User" , "description" : "Describes a system user." , "supportedOperation" : [ { "method" : "PUT" , "title" : "Create new user" , "description" : "Creates a brand new user." , "expects" : "http://api.example.com/vocab#User" , "returns" : "http://api.example.com/vocab#User" , "returnsHeader" : [ { "headerName" : "Content-Type" , "possibleValue" : [ "text/turtle" , "application/ld+json" ], "closedSet" : true } "Content-Length" ], "expectsHeader" : [ "Authorization" , { "headerName" : "Content-Type" , "possibleValue" : [ "image/gif" , "image/png" ], "closedSet" : true } ] } ], "supportedProperty" : [ { "property" : "http://api.example.com/vocab#login" , "writable" : true , "readable" : true , "required" : true } ] } ] }
7.35. hydra:search
+| Name: + | search + |
|---|---|
| Summary: + | A Iri template that can be used to query a collection. + |
| Domain: + | Resource + |
| Range: + | IriTemplate + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api/posts" , "@type" : "Collection" , "view" : { "@id" : "http://api.example.com/api/posts?skip=10" , "@type" : "PartialCollectionView" , "first" : "http://api.example.com/api/posts" , "last" : "http://api.example.com/api/posts?skip=100" , "previous" : "http://api.example.com/api/posts" , "next" : "http://api.example.com/api/posts?skip=20" , "totalItems" : 10 , }, "totalItems" : 100 , "member" : [ { "@id" : "http://api.example.com/api/posts/10" }, { "@id" : "http://api.example.com/api/posts/11" }, { "@id" : "http://api.example.com/api/posts/12" }, { "@id" : "http://api.example.com/api/posts/13" }, { "@id" : "http://api.example.com/api/posts/14" }, { "@id" : "http://api.example.com/api/posts/15" }, { "@id" : "http://api.example.com/api/posts/16" }, { "@id" : "http://api.example.com/api/posts/17" }, { "@id" : "http://api.example.com/api/posts/18" }, { "@id" : "http://api.example.com/api/posts/19" } ], "search" : { "template" : "/api/posts{?search,limit,offset}" , "resolveRelativeUsing" : "hydra:Rfc3986" , "mapping" : [ { "variable" : "search" , "property" : "hydra:freetextQuery" , "required" : true , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "limit" , "property" : "hydra:limit" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "offset" , "property" : "hydra:offset" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" } ] } }
7.36. hydra:statusCode
+| Name: + | statusCode + |
|---|---|
| Summary: + | The response status code. Please note it may happen this + value will be different to actual status code received. + |
| Domain: + | Status + |
| Range: + | xsd:integer
+ |
+HTTP / 1.1 400 Bad request Content-Type : application/problem+json Link : <http://www.w3.org/ns/hydra/error>; rel="http://www.w3.org/ns/json-ld#context" { "type" : "https://api.example.com/vocab#NullReferenceException" , "@type" : "http://www.w3.org/ns/hydra/core#Error" , "title" : "The request cannot be processed." , "detail" : "Provided value cannot be 'null'." , "instance" : "http://api.example.com/api/posts" , "status" : 404 }
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api/posts/1" , "operation" : [ { "method" : "DELETE" , "title" : "Remove" , "description" : "Removes post no. 1" , "possibleStatus" : [ { "@type" : "Status" , "statusCode" : 303 } ] } ] }
7.37. hydra:subject
+| Name: + | subject + |
|---|---|
| Summary: + | The subject. + |
| Min cardinality: + | 1 + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api/posts/1/comments" , "@type" : "Collection" , "memberAssertion" : [ { "subject" : "http://api.example.com/api/posts/1" , "property" : "http://api.example.com/vocab#comment" } ] }
7.38. hydra:supportedClass
+| Name: + | supportedClass + |
|---|---|
| Summary: + | A class known to be supported by the Web API. + |
| Domain: + | ApiDocumentation + |
| Range: + | rdfs:Class
+ |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api?documentation" , "@type" : "ApiDocumentation" , "entrypoint" : "http://api.example.com/api" , "extension" : "https://w3id.org/hydra/extension#shacl" , "supportedClass" : [ { "@id" : "http://api.example.com/vocab#User" , "title" : "User" , "description" : "Describes a system user." , "supportedOperation" : [ { "method" : "PUT" , "title" : "Create new user" , "description" : "Creates a brand new user." , "expects" : "http://api.example.com/vocab#User" , "returns" : "http://api.example.com/vocab#User" , "returnsHeader" : [ { "headerName" : "Content-Type" , "possibleValue" : [ "text/turtle" , "application/ld+json" ], "closedSet" : true } "Content-Length" ], "expectsHeader" : [ "Authorization" , { "headerName" : "Content-Type" , "possibleValue" : [ "image/gif" , "image/png" ], "closedSet" : true } ] } ], "supportedProperty" : [ { "property" : "http://api.example.com/vocab#login" , "writable" : true , "readable" : true , "required" : true } ] } ] }
7.39. hydra:supportedOperation
+| Name: + | supportedOperation + |
|---|---|
| Summary: + | An operation supported by instances of the specific Hydra + class, or the target of the Hydra link, or Iri template. + |
| Domain includes: + | rdfs:Class, Class, Link, TemplatedLink, SupportedProperty
+ |
| Range: + | Operation + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api?documentation" , "@type" : "ApiDocumentation" , "entrypoint" : "http://api.example.com/api" , "extension" : "https://w3id.org/hydra/extension#shacl" , "supportedClass" : [ { "@id" : "http://api.example.com/vocab#User" , "title" : "User" , "description" : "Describes a system user." , "supportedOperation" : [ { "method" : "PUT" , "title" : "Create new user" , "description" : "Creates a brand new user." , "expects" : "http://api.example.com/vocab#User" , "returns" : "http://api.example.com/vocab#User" , "returnsHeader" : [ { "headerName" : "Content-Type" , "possibleValue" : [ "text/turtle" , "application/ld+json" ], "closedSet" : true } "Content-Length" ], "expectsHeader" : [ "Authorization" , { "headerName" : "Content-Type" , "possibleValue" : [ "image/gif" , "image/png" ], "closedSet" : true } ] } ], "supportedProperty" : [ { "property" : "http://api.example.com/vocab#login" , "writable" : true , "readable" : true , "required" : true } ] } ] }
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api/posts" , "@type" : "Collection" , "view" : { "@id" : "http://api.example.com/api/posts?skip=10" , "@type" : "PartialCollectionView" , "first" : "http://api.example.com/api/posts" , "last" : "http://api.example.com/api/posts?skip=100" , "previous" : "http://api.example.com/api/posts" , "next" : "http://api.example.com/api/posts?skip=20" , "totalItems" : 10 , }, "totalItems" : 100 , "member" : [ { "@id" : "http://api.example.com/api/posts/10" }, { "@id" : "http://api.example.com/api/posts/11" }, { "@id" : "http://api.example.com/api/posts/12" }, { "@id" : "http://api.example.com/api/posts/13" }, { "@id" : "http://api.example.com/api/posts/14" }, { "@id" : "http://api.example.com/api/posts/15" }, { "@id" : "http://api.example.com/api/posts/16" }, { "@id" : "http://api.example.com/api/posts/17" }, { "@id" : "http://api.example.com/api/posts/18" }, { "@id" : "http://api.example.com/api/posts/19" } ], "search" : { "template" : "/api/posts{?search}" , "resolveRelativeUsing" : "hydra:Rfc3986" , "supportedOperation" : { "method" : "POST" }, "mapping" : [ { "variable" : "search" , "property" : "hydra:freetextQuery" , "required" : true , "variableRepresentation" : "hydra:BasicRepresentation" } ] } }
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@graph" : [ { "@id" : "http://api.example.com/api/posts/1" , "http://api.example.com/vocab#comment" : "http://api.example.com/api/posts/1/comments" }, { "@id" : "http://api.example.com/vocab#comment" , "@type" : "hydra:Link" , "supportedOperation" : { "method" : "GET" , "returns" : "http://api.example.com/vocab#Comment } } ]}
7.40. hydra:supportedProperty
+| Name: + | supportedProperty + |
|---|---|
| Summary: + | The properties known to be supported by a Hydra class. + |
| Domain: + | rdfs:Class
+ |
| Range: + | SupportedProperty + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api?documentation" , "@type" : "ApiDocumentation" , "entrypoint" : "http://api.example.com/api" , "extension" : "https://w3id.org/hydra/extension#shacl" , "supportedClass" : [ { "@id" : "http://api.example.com/vocab#User" , "title" : "User" , "description" : "Describes a system user." , "supportedOperation" : [ { "method" : "PUT" , "title" : "Create new user" , "description" : "Creates a brand new user." , "expects" : "http://api.example.com/vocab#User" , "returns" : "http://api.example.com/vocab#User" , "returnsHeader" : [ { "headerName" : "Content-Type" , "possibleValue" : [ "text/turtle" , "application/ld+json" ], "closedSet" : true } "Content-Length" ], "expectsHeader" : [ "Authorization" , { "headerName" : "Content-Type" , "possibleValue" : [ "image/gif" , "image/png" ], "closedSet" : true } ] } ], "supportedProperty" : [ { "property" : "http://api.example.com/vocab#login" , "writable" : true , "readable" : true , "required" : true } ] } ] }
7.41. hydra:template
+| Name: + | template + |
|---|---|
| Summary: + | A templated string with placeholders. The literal’s + datatype indicates the template syntax; if not specified, + hydra:Rfc6570Template is assumed. + |
| Min cardinality: + | 1 + |
| Max cardinality: + | 1 + |
| Domain: + | IriTemplate + |
| Range: + | Rfc6570Template + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api/posts" , "@type" : "Collection" , "view" : { "@id" : "http://api.example.com/api/posts?skip=10" , "@type" : "PartialCollectionView" , "first" : "http://api.example.com/api/posts" , "last" : "http://api.example.com/api/posts?skip=100" , "previous" : "http://api.example.com/api/posts" , "next" : "http://api.example.com/api/posts?skip=20" , "totalItems" : 10 , }, "totalItems" : 100 , "member" : [ { "@id" : "http://api.example.com/api/posts/10" }, { "@id" : "http://api.example.com/api/posts/11" }, { "@id" : "http://api.example.com/api/posts/12" }, { "@id" : "http://api.example.com/api/posts/13" }, { "@id" : "http://api.example.com/api/posts/14" }, { "@id" : "http://api.example.com/api/posts/15" }, { "@id" : "http://api.example.com/api/posts/16" }, { "@id" : "http://api.example.com/api/posts/17" }, { "@id" : "http://api.example.com/api/posts/18" }, { "@id" : "http://api.example.com/api/posts/19" } ], "search" : { "template" : "/api/posts{?search,limit,offset}" , "resolveRelativeUsing" : "hydra:Rfc3986" , "mapping" : [ { "variable" : "search" , "property" : "hydra:freetextQuery" , "required" : true , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "limit" , "property" : "hydra:limit" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "offset" , "property" : "hydra:offset" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" } ] } }
7.42. hydra:title
+| Name: + | title + |
|---|---|
| Summary: + | A title, often used along with a description. + |
| Max cardinality: + | 1 + |
| Domain includes: + | ApiDocumentation, Status, Class, SupportedProperty, Operation, Link, TemplatedLink + |
| Range: + | xsd:string
+ |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api?documentation" , "@type" : "ApiDocumentation" , "entrypoint" : "http://api.example.com/api" , "extension" : "https://w3id.org/hydra/extension#shacl" , "supportedClass" : [ { "@id" : "http://api.example.com/vocab#User" , "title" : "User" , "description" : "Describes a system user." , "supportedOperation" : [ { "method" : "PUT" , "title" : "Create new user" , "description" : "Creates a brand new user." , "expects" : "http://api.example.com/vocab#User" , "returns" : "http://api.example.com/vocab#User" , "returnsHeader" : [ { "headerName" : "Content-Type" , "possibleValue" : [ "text/turtle" , "application/ld+json" ], "closedSet" : true } "Content-Length" ], "expectsHeader" : [ "Authorization" , { "headerName" : "Content-Type" , "possibleValue" : [ "image/gif" , "image/png" ], "closedSet" : true } ] } ], "supportedProperty" : [ { "property" : "http://api.example.com/vocab#login" , "writable" : true , "readable" : true , "required" : true } ] } ] }
7.43. hydra:totalItems
+| Name: + | totalItems + |
|---|---|
| Summary: + | The total number of items referenced by a collection. + |
| Max cardinality: + | 1 + |
| Domain: + | Collection + |
| Range: + | xsd:integer
+ |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api/posts" , "@type" : "Collection" , "view" : { "@id" : "http://api.example.com/api/posts?skip=10" , "@type" : "PartialCollectionView" , "first" : "http://api.example.com/api/posts" , "last" : "http://api.example.com/api/posts?skip=100" , "previous" : "http://api.example.com/api/posts" , "next" : "http://api.example.com/api/posts?skip=20" , "totalItems" : 10 , }, "totalItems" : 100 , "member" : [ { "@id" : "http://api.example.com/api/posts/10" }, { "@id" : "http://api.example.com/api/posts/11" }, { "@id" : "http://api.example.com/api/posts/12" }, { "@id" : "http://api.example.com/api/posts/13" }, { "@id" : "http://api.example.com/api/posts/14" }, { "@id" : "http://api.example.com/api/posts/15" }, { "@id" : "http://api.example.com/api/posts/16" }, { "@id" : "http://api.example.com/api/posts/17" }, { "@id" : "http://api.example.com/api/posts/18" }, { "@id" : "http://api.example.com/api/posts/19" } ], "search" : { "template" : "/api/posts{?search,limit,offset}" , "resolveRelativeUsing" : "hydra:Rfc3986" , "mapping" : [ { "variable" : "search" , "property" : "hydra:freetextQuery" , "required" : true , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "limit" , "property" : "hydra:limit" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "offset" , "property" : "hydra:offset" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" } ] } }
7.44. hydra:variable
+| Name: + | variable + |
|---|---|
| Summary: + | An Iri template variable. + |
| Min cardinality: + | 1 + |
| Max cardinality: + | 1 + |
| Domain: + | IriTemplateMapping + |
| Range: + | xsd:string
+ |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api/posts" , "@type" : "Collection" , "view" : { "@id" : "http://api.example.com/api/posts?skip=10" , "@type" : "PartialCollectionView" , "first" : "http://api.example.com/api/posts" , "last" : "http://api.example.com/api/posts?skip=100" , "previous" : "http://api.example.com/api/posts" , "next" : "http://api.example.com/api/posts?skip=20" , "totalItems" : 10 , }, "totalItems" : 100 , "member" : [ { "@id" : "http://api.example.com/api/posts/10" }, { "@id" : "http://api.example.com/api/posts/11" }, { "@id" : "http://api.example.com/api/posts/12" }, { "@id" : "http://api.example.com/api/posts/13" }, { "@id" : "http://api.example.com/api/posts/14" }, { "@id" : "http://api.example.com/api/posts/15" }, { "@id" : "http://api.example.com/api/posts/16" }, { "@id" : "http://api.example.com/api/posts/17" }, { "@id" : "http://api.example.com/api/posts/18" }, { "@id" : "http://api.example.com/api/posts/19" } ], "search" : { "template" : "/api/posts{?search,limit,offset}" , "resolveRelativeUsing" : "hydra:Rfc3986" , "mapping" : [ { "variable" : "search" , "property" : "hydra:freetextQuery" , "required" : true , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "limit" , "property" : "hydra:limit" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "offset" , "property" : "hydra:offset" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" } ] } }
7.45. hydra:variableRepresentation
+| Name: + | variableRepresentation + |
|---|---|
| Summary: + | The representation format to use when expanding + the Iri template. + |
| Max cardinality: + | 1 + |
| Domain includes: + | IriTemplateMapping, IriTemplate + |
| Range: + | VariableRepresentation + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api/posts" , "@type" : "Collection" , hydra: view"view" : { "@id" : "http://api.example.com/api/posts?skip=10" , "@type" : "PartialCollectionView" , "first" : "http://api.example.com/api/posts" , "last" : "http://api.example.com/api/posts?skip=100" , "previous" : "http://api.example.com/api/posts" , "next" : "http://api.example.com/api/posts?skip=20" , "totalItems" : 10 , }, "totalItems" : 100 , "member" : [ { "@id" : "http://api.example.com/api/posts/10" }, { "@id" : "http://api.example.com/api/posts/11" }, { "@id" : "http://api.example.com/api/posts/12" }, { "@id" : "http://api.example.com/api/posts/13" }, { "@id" : "http://api.example.com/api/posts/14" }, { "@id" : "http://api.example.com/api/posts/15" }, { "@id" : "http://api.example.com/api/posts/16" }, { "@id" : "http://api.example.com/api/posts/17" }, { "@id" : "http://api.example.com/api/posts/18" }, { "@id" : "http://api.example.com/api/posts/19" } ], "search" : { "template" : "/api/posts{?search,limit,offset}" , "resolveRelativeUsing" : "hydra:Rfc3986" , "variableRepresentation" : "hydra:BasicRepresentation" , "mapping" : [ { "variable" : "search" , "property" : "hydra:freetextQuery" , "required" : true , "variableRepresentation" : "hydra:ExplicitRepresentation" }, { "variable" : "limit" , "property" : "hydra:limit" , "required" : false }, { "variable" : "offset" , "property" : "hydra:offset" , "required" : false } ] } }
7.46. hydra:view
+| Name: + | view + |
|---|---|
| Summary: + | A specific view of a resource. + |
| Max cardinality: + | 1 + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api/posts" , "@type" : "Collection" , "view" : { "@id" : "http://api.example.com/api/posts?skip=10" , "@type" : "PartialCollectionView" , "first" : "http://api.example.com/api/posts" , "last" : "http://api.example.com/api/posts?skip=100" , "previous" : "http://api.example.com/api/posts" , "next" : "http://api.example.com/api/posts?skip=20" , "totalItems" : 10 , }, "totalItems" : 100 , "member" : [ { "@id" : "http://api.example.com/api/posts/10" }, { "@id" : "http://api.example.com/api/posts/11" }, { "@id" : "http://api.example.com/api/posts/12" }, { "@id" : "http://api.example.com/api/posts/13" }, { "@id" : "http://api.example.com/api/posts/14" }, { "@id" : "http://api.example.com/api/posts/15" }, { "@id" : "http://api.example.com/api/posts/16" }, { "@id" : "http://api.example.com/api/posts/17" }, { "@id" : "http://api.example.com/api/posts/18" }, { "@id" : "http://api.example.com/api/posts/19" } ], "search" : { "template" : "/api/posts{?search,limit,offset}" , "resolveRelativeUsing" : "hydra:Rfc3986" , "mapping" : [ { "variable" : "search" , "property" : "hydra:freetextQuery" , "required" : true , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "limit" , "property" : "hydra:limit" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" }, { "variable" : "offset" , "property" : "hydra:offset" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" } ] } }
7.47. hydra:writable
+| Name: + | writable + |
|---|---|
| Summary: + | True if the client can change the property’s value, + false otherwise. + |
| Max cardinality: + | 1 + |
| Domain: + | SupportedProperty + |
| Range: + | xsd:boolean
+ |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api?documentation" , "@type" : "ApiDocumentation" , "entrypoint" : "http://api.example.com/api" , "extension" : "https://w3id.org/hydra/extension#shacl" , "supportedClass" : [ { "@id" : "http://api.example.com/vocab#User" , "label" : "User" , "description" : "Describes a system user." , "supportedOperation" : [ { "method" : "PUT" , "label" : "Create new user" , "description" : "Creates a brand new user." , "expects" : "http://api.example.com/vocab#User" , "returns" : "http://api.example.com/vocab#User" , "returnsHeader" : [ { "headerName" : "Content-Type" , "possibleValue" : [ "text/turtle" , "application/ld+json" ], "closedSet" : true } "Content-Length" ], "expectsHeader" : [ "Authorization" , { "headerName" : "Content-Type" , "possibleValue" : [ "image/gif" , "image/png" ], "closedSet" : true } ] } ], "supportedProperty" : [ { "property" : "http://api.example.com/vocab#login" , "writable" : true , "readable" : true , "required" : true } ] } ] }
8. Named instances
+8.1. hydra:BasicRepresentation
+| Name: + | BasicRepresentation + |
|---|---|
| Summary: + | A representation that serializes just the lexical form of a variable value, + but omits language and type information. + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api/posts" , "@type" : "Collection" , "view" : { "@id" : "http://api.example.com/api/posts?skip=10" , "@type" : "PartialCollectionView" , "first" : "http://api.example.com/api/posts" , "last" : "http://api.example.com/api/posts?skip=100" , "previous" : "http://api.example.com/api/posts" , "next" : "http://api.example.com/api/posts?skip=20" , "totalItems" : 10 , }, "totalItems" : 100 , "member" : [ { "@id" : "http://api.example.com/api/posts/10" }, { "@id" : "http://api.example.com/api/posts/11" }, { "@id" : "http://api.example.com/api/posts/12" }, { "@id" : "http://api.example.com/api/posts/13" }, { "@id" : "http://api.example.com/api/posts/14" }, { "@id" : "http://api.example.com/api/posts/15" }, { "@id" : "http://api.example.com/api/posts/16" }, { "@id" : "http://api.example.com/api/posts/17" }, { "@id" : "http://api.example.com/api/posts/18" }, { "@id" : "http://api.example.com/api/posts/19" } ], "search" : { "template" : "/api/posts{?search}" , "resolveRelativeUsing" : "hydra:Rfc3986" , "mapping" : [ { "variable" : "search" , "property" : "hydra:freetextQuery" , "required" : true , "variableRepresentation" : "hydra:BasicRepresentation" } ] } }
8.2. hydra:ExplicitRepresentation
+| Name: + | ExplicitRepresentation + |
|---|---|
| Summary: + | A representation that serializes a variable value including its language + and type information and thus differentiating between IRIs and literals. + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api/posts" , "@type" : "Collection" , "view" : { "@id" : "http://api.example.com/api/posts?skip=10" , "@type" : "PartialCollectionView" , "first" : "http://api.example.com/api/posts" , "last" : "http://api.example.com/api/posts?skip=100" , "previous" : "http://api.example.com/api/posts" , "next" : "http://api.example.com/api/posts?skip=20" , "totalItems" : 10 , }, "totalItems" : 100 , "member" : [ { "@id" : "http://api.example.com/api/posts/10" }, { "@id" : "http://api.example.com/api/posts/11" }, { "@id" : "http://api.example.com/api/posts/12" }, { "@id" : "http://api.example.com/api/posts/13" }, { "@id" : "http://api.example.com/api/posts/14" }, { "@id" : "http://api.example.com/api/posts/15" }, { "@id" : "http://api.example.com/api/posts/16" }, { "@id" : "http://api.example.com/api/posts/17" }, { "@id" : "http://api.example.com/api/posts/18" }, { "@id" : "http://api.example.com/api/posts/19" } ], "search" : { "template" : "/api/posts{?search}" , "resolveRelativeUsing" : "hydra:Rfc3986" , "mapping" : [ { "variable" : "search" , "property" : "hydra:freetextQuery" , "required" : true , "variableRepresentation" : "hydra:ExplicitRepresentation" } ] } }
8.3. hydra:LinkContext
+| Name: + | LinkContext + |
|---|---|
| Summary: + | States that the link’s context IRI, as defined in RFC 5988, should be used + as the base Uri. + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api/posts" , "@type" : "Collection" , "view" : { "@id" : "http://api.example.com/api/posts?skip=10" , "@type" : "PartialCollectionView" , "first" : "http://api.example.com/api/posts" , "last" : "http://api.example.com/api/posts?skip=100" , "previous" : "http://api.example.com/api/posts" , "next" : "http://api.example.com/api/posts?skip=20" , "totalItems" : 10 , }, "totalItems" : 100 , "member" : [ { "@id" : "http://api.example.com/api/posts/10" }, { "@id" : "http://api.example.com/api/posts/11" }, { "@id" : "http://api.example.com/api/posts/12" }, { "@id" : "http://api.example.com/api/posts/13" }, { "@id" : "http://api.example.com/api/posts/14" }, { "@id" : "http://api.example.com/api/posts/15" }, { "@id" : "http://api.example.com/api/posts/16" }, { "@id" : "http://api.example.com/api/posts/17" }, { "@id" : "http://api.example.com/api/posts/18" }, { "@id" : "http://api.example.com/api/posts/19" } ], "search" : { "template" : { "@value" : "/api/posts{?search}" , "@type" : "hydra:Rfc6570Template" }, "resolveRelativeUsing" : "hydra:LinkContext" , "mapping" : [ { "variable" : "search" , "property" : "hydra:freetextQuery" , "required" : true , "variableRepresentation" : "hydra:BasicRepresentation" } ] } }
8.4. hydra:Rfc3986
+| Name: + | Rfc3986 + |
|---|---|
| Summary: + | States that the link’s context IRI, as defined in RFC 5988, should be used + as the base Uri. + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api/posts" , "@type" : "Collection" , "view" : { "@id" : "http://api.example.com/api/posts?skip=10" , "@type" : "PartialCollectionView" , "first" : "http://api.example.com/api/posts" , "last" : "http://api.example.com/api/posts?skip=100" , "previous" : "http://api.example.com/api/posts" , "next" : "http://api.example.com/api/posts?skip=20" , "totalItems" : 10 , }, "totalItems" : 100 , "member" : [ { "@id" : "http://api.example.com/api/posts/10" }, { "@id" : "http://api.example.com/api/posts/11" }, { "@id" : "http://api.example.com/api/posts/12" }, { "@id" : "http://api.example.com/api/posts/13" }, { "@id" : "http://api.example.com/api/posts/14" }, { "@id" : "http://api.example.com/api/posts/15" }, { "@id" : "http://api.example.com/api/posts/16" }, { "@id" : "http://api.example.com/api/posts/17" }, { "@id" : "http://api.example.com/api/posts/18" }, { "@id" : "http://api.example.com/api/posts/19" } ], "search" : { "template" : { "@value" : "/api/posts{?search}" , "@type" : "hydra:Rfc6570Template" }, "resolveRelativeUsing" : "hydra:Rfc3986" , "mapping" : [ { "variable" : "search" , "property" : "hydra:freetextQuery" , "required" : true , "variableRepresentation" : "hydra:BasicRepresentation" } ] } }
8.5. hydra:Unavailable
+| Name: + | Unavailable + |
|---|---|
| Summary: + | States an operation previously announced is unavailable in current circumstances. + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/doc/" , "@type" : "Collection" , "retractedOperation" : [ { "@type" : "Operation" , "method" : "POST" , "expects" : "http://api.example.com/doc/#Upload" , "reason" : "Unavailable" } ] }
8.6. hydra:Unauthorized
+| Name: + | Unauthorized + |
|---|---|
| Summary: + | States an operation previously announced should not be invoked + as the current user is not authorized to invoke it. + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/doc/" , "@type" : "Collection" , "retractedOperation" : [ { "@type" : "Operation" , "method" : "POST" , "expects" : "http://api.example.com/doc/#Upload" , "reason" : "Unauthorized" } ] }
9. Data types
+9.1. hydra:Rfc6570Template
+| Name: + | Rfc6570Template + |
|---|---|
| Summary: + | An IRI template as defined by [RFC6570]. + |
+{ "@context" : "http://www.w3.org/ns/hydra/context.jsonld" , "@id" : "http://api.example.com/api/posts" , "@type" : "Collection" , "view" : { "@id" : "http://api.example.com/api/posts?skip=10" , "@type" : "PartialCollectionView" , "first" : "http://api.example.com/api/posts" , "last" : "http://api.example.com/api/posts?skip=100" , "previous" : "http://api.example.com/api/posts" , "next" : "http://api.example.com/api/posts?skip=20" , "totalItems" : 10 , }, "totalItems" : 100 , "member" : [ { "@id" : "http://api.example.com/api/posts/10" }, { "@id" : "http://api.example.com/api/posts/11" }, { "@id" : "http://api.example.com/api/posts/12" }, { "@id" : "http://api.example.com/api/posts/13" }, { "@id" : "http://api.example.com/api/posts/14" }, { "@id" : "http://api.example.com/api/posts/15" }, { "@id" : "http://api.example.com/api/posts/16" }, { "@id" : "http://api.example.com/api/posts/17" }, { "@id" : "http://api.example.com/api/posts/18" }, { "@id" : "http://api.example.com/api/posts/19" } ], "search" : { "template" : { "@value" : "/api/posts{?search,limit,offset}" , "@type" : "hydra:Rfc6570Template" }, "resolveRelativeUsing" : "hydra:Rfc3986" , "mapping" : [ { "variable" : "search" , "property" : "hydra:freetextQuery" , "required" : true , "variableRepresentation" : "hydra:BasicRepresentation"" }, { " variable": " limit ", " propert y": " hydra: limit ", " required": false, " variableRepresentat ion ": " hydra: BasicRepresentat ion "" }, { "variable" : "offset" , "property" : "hydra:offset" , "required" : false , "variableRepresentation" : "hydra:BasicRepresentation" " } ] }}
10. Acknowledgements
+Note: This section is non-normative.
+The authors would like to thank the following individuals for contributing +their ideas and providing feedback for writing this specification: +Arnau Siches, elf Pavlik, Mark Baker, Martijn Faassen, +Matthias Lehmann, Ruben Verborgh, Ryan J. McDonough, Sam Goto, +Thomas Hoppe, @wasabiwimp (on GitHub).
+Special thanks to Tomasz Pluskiewicz.
+11. The Hydra in JSON-LD
+Note: This section is non-normative.
++{ "@context" : { "hydra" : "http://www.w3.org/ns/hydra/core#" , "rdf" : "http://www.w3.org/1999/02/22-rdf-syntax-ns#" , "rdfs" : "http://www.w3.org/2000/01/rdf-schema#" , "xsd" : "http://www.w3.org/2001/XMLSchema#" , "owl" : "http://www.w3.org/2002/07/owl#" , "vs" : "http://www.w3.org/2003/06/sw-vocab-status/ns#" , "dc" : "http://purl.org/dc/terms/" , "cc" : "http://creativecommons.org/ns#" , "schema" : "http://schema.org/" , "apiDocumentation" : "hydra:apiDocumentation" , "ApiDocumentation" : "hydra:ApiDocumentation" , "title" : "hydra:title" , "description" : "hydra:description" , "entrypoint" : { "@id" : "hydra:entrypoint" , "@type" : "@id" }, "supportedClass" : { "@id" : "hydra:supportedClass" , "@type" : "@vocab" }, "Class" : "hydra:Class" , "supportedProperty" : { "@id" : "hydra:supportedProperty" , "@type" : "@id" }, "SupportedProperty" : "hydra:SupportedProperty" , "property" : { "@id" : "hydra:property" , "@type" : "@vocab" }, "required" : "hydra:required" , "readable" : "hydra:readable" , "writable" : "hydra:writable" , "writeable" : "hydra:writeable" , "supportedOperation" : { "@id" : "hydra:supportedOperation" , "@type" : "@id" }, "Operation" : "hydra:Operation" , "method" : "hydra:method" , "expects" : { "@id" : "hydra:expects" , "@type" : "@vocab" }, "returns" : { "@id" : "hydra:returns" , "@type" : "@vocab" }, "retractedOperation" : { "@id" : "hydra:retractedOperation" , "@type" : "@vocab" }, "reason" : { "@id" : "hydra:reason" , "@type" : "@vocab" }, "RetractedOperationSpecification" : "hydra:RetractedOperationSpecification" , "UnavailabilityReason" : "hydra:UnavailabilityReason" , "Unavailable" : "hydra:Unavailable" , "Unauthorized" : "hydra:Unauthorized" , "possibleStatus" : { "@id" : "hydra:possibleStatus" , "@type" : "@id" }, "Status" : "hydra:Status" , "statusCode" : "hydra:statusCode" , "Error" : "hydra:Error" , "Resource" : "hydra:Resource" , "operation" : "hydra:operation" , "Collection" : "hydra:Collection" , "collection" : "hydra:collection" , "member" : { "@id" : "hydra:member" , "@type" : "@id" }, "memberAssertion" : "hydra:memberAssertion" , "manages" : "hydra:manages" , "subject" : { "@id" : "hydra:subject" , "@type" : "@vocab" }, "object" : { "@id" : "hydra:object" , "@type" : "@vocab" }, "search" : "hydra:search" , "freetextQuery" : "hydra:freetextQuery" , "view" : { "@id" : "hydra:view" , "@type" : "@id" }, "PartialCollectionView" : "hydra:PartialCollectionView" , "totalItems" : "hydra:totalItems" , "first" : { "@id" : "hydra:first" , "@type" : "@id" }, "last" : { "@id" : "hydra:last" , "@type" : "@id" }, "next" : { "@id" : "hydra:next" , "@type" : "@id" }, "previous" : { "@id" : "hydra:previous" , "@type" : "@id" }, "Link" : "hydra:Link" , "TemplatedLink" : "hydra:TemplatedLink" , "IriTemplate" : "hydra:IriTemplate" , "template" : "hydra:template" , "Rfc6570Template" : "hydra:Rfc6570Template" , "variableRepresentation" : { "@id" : "hydra:variableRepresentation" , "@type" : "@vocab" }, "VariableRepresentation" : "hydra:VariableRepresentation" , "BasicRepresentation" : "hydra:BasicRepresentation" , "ExplicitRepresentation" : "hydra:ExplicitRepresentation" , "mapping" : "hydra:mapping" , "IriTemplateMapping" : "hydra:IriTemplateMapping" , "variable" : "hydra:variable" , "offset" : { "@id" : "hydra:offset" , "@type" : "xsd:nonNegativeInteger" }, "limit" : { "@id" : "hydra:limit" , "@type" : "xsd:nonNegativeInteger" }, "pageIndex" : { "@id" : "hydra:pageIndex" , "@type" : "xsd:nonNegativeInteger" }, "pageReference" : { "@id" : "hydra:pageReference" }, "returnsHeader" : { "@id" : "hydra:returnsHeader" , "@type" : "xsd:string" }, "expectsHeader" : { "@id" : "hydra:expectsHeader" , "@type" : "xsd:string" }, "HeaderSpecification" : "hydra:HeaderSpecification" , "headerName" : "hydra:headerName" , "possibleValue" : "hydra:possibleValue" , "closedSet" : { "@id" : "hydra:possibleValue" , "@type" : "xsd:boolean" }, "name" : { "@id" : "hydra:name" , "@type" : "xsd:string" }, "extension" : { "@id" : "hydra:extension" , "@type" : "@id" }, "isDefinedBy" : { "@id" : "rdfs:isDefinedBy" , "@type" : "@id" }, "defines" : { "@reverse" : "rdfs:isDefinedBy" }, "comment" : "rdfs:comment" , "label" : "rdfs:label" , "preferredPrefix" : "http://purl.org/vocab/vann/preferredNamespacePrefix" , "cc:license" : { "@type" : "@id" }, "cc:attributionURL" : { "@type" : "@id" }, "domain" : { "@id" : "rdfs:domain" , "@type" : "@vocab" }, "range" : { "@id" : "rdfs:range" , "@type" : "@vocab" }, "subClassOf" : { "@id" : "rdfs:subClassOf" , "@type" : "@vocab" }, "subPropertyOf" : { "@id" : "rdfs:subPropertyOf" , "@type" : "@vocab" }, "seeAlso" : { "@id" : "rdfs:seeAlso" , "@type" : "@id" }, "domainIncludes" : { "@id" : "schema:domainIncludes" , "@type" : "@id" }, "rangeIncludes" : { "@id" : "schema:rangeIncludes" , "@type" : "@id" } }, "@id" : "http://www.w3.org/ns/hydra/core" , "@type" : "owl:Ontology" , "label" : "The Hydra Core Vocabulary" , "comment" : "A lightweight vocabulary for hypermedia-driven Web APIs." , "seeAlso" : "https://www.hydra-cg.com/spec/latest/core/" , "preferredPrefix" : "hydra" , "dc:description" : "The Hydra Core Vocabulary is a lightweight vocabulary to create hypermedia-driven Web APIs. By specifying a number of concepts commonly used in Web APIs it enables the creation of generic API clients." , "dc:rights" : "Copyright © 2012-2014 the Contributors to the Hydra Core Vocabulary Specification" , "dc:publisher" : "Hydra W3C Community Group" , "cc:license" : "http://creativecommons.org/licenses/by/4.0/" , "cc:attributionName" : "Hydra W3C Community Group" , "cc:attributionURL" : "http://www.hydra-cg.com/" , "defines" : [ { "@id" : "hydra:Resource" , "@type" : "hydra:Class" , "label" : "Hydra Resource" , "comment" : "The class of dereferenceable resources by means a client can attempt to dereference; however, the received responses should still be verified." , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:Class" , "@type" : [ "hydra:Resource" , "rdfs:Class" ], "subClassOf" : [ "rdfs:Class" ], "label" : "Hydra Class" , "comment" : "The class of Hydra classes." , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:Link" , "@type" : "hydra:Class" , "subClassOf" : [ "hydra:Resource" , "rdf:Property" ], "label" : "Link" , "comment" : "The class of properties representing links." , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:apiDocumentation" , "@type" : "hydra:Link" , "label" : "apiDocumentation" , "comment" : "A link to the API documentation." , "range" : "hydra:ApiDocumentation" , "domain" : "hydra:Resource" , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:ApiDocumentation" , "@type" : "hydra:Class" , "subClassOf" : "hydra:Resource" , "label" : "ApiDocumentation" , "comment" : "The Hydra API documentation class." , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:entrypoint" , "@type" : "hydra:Link" , "label" : "entrypoint" , "comment" : "A link to main entry point of the Web API." , "domain" : "hydra:ApiDocumentation" , "range" : "hydra:Resource" , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:supportedClass" , "@type" : "hydra:Link" , "label" : "supported classes" , "comment" : "A class known to be supported by the Web API." , "domain" : "hydra:ApiDocumentation" , "range" : "rdfs:Class" , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:retractedOperation" , "@type" : "rdf:Property" , "label" : "retracted operation" , "comment" : "Retracts available operations." , "range" : "hydra:RetractedOperationSpecification" , "domain" : "hydra:Resource" , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:RetractedOperationSpecification" , "@type" : "hydra:Class" , "label" : "retracted operation specification" , "comment" : "Describes which and why an operation is retracted." , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:reason" , "@type" : "rdf:Property" , "label" : "reason" , "comment" : "Reason of why the operation is retracted." , "range" : "hydra:UnavailabilityReason" , "domain" : "hydra:RetractedOperationSpecification" , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:UnavailabilityReason" , "@type" : "hydra:Class" , "label" : "Unavailability reason" , "comment" : "Provides reasons why the operation cannot be invoked." , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:Unavailable" , "@type" : "hydra:UnavailabilityReason" , "label" : "Unavailable" , "comment" : "States an operation previously announced is unavailable in current circumstances." , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:Unauthorized" , "@type" : "hydra:Availability" , "label" : "Unauthorized" , "comment" : "States an operation previously announced should not be invoked as the current user is not authorized to invoke it." , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:possibleStatus" , "@type" : "hydra:Link" , "label" : "possible status" , "comment" : "A status that might be returned by the Web API (other statuses should be expected and properly handled as well)." , "range" : "hydra:Status" , "domainIncludes" : [ "hydra:ApiDocumentation" , "hydra:Operation" , "hydra:RetractedOperationSpecification" ], "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:supportedProperty" , "@type" : "hydra:Link" , "label" : "supported properties" , "comment" : "The properties known to be supported by a Hydra class." , "domain" : "rdfs:Class" , "range" : "hydra:SupportedProperty" , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:SupportedProperty" , "@type" : "hydra:Class" , "label" : "Supported Property" , "comment" : "A property known to be supported by a Hydra class." , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:property" , "@type" : "rdf:Property" , "label" : "property" , "comment" : "A property." , "range" : "rdf:Property" , "domainIncludes" : [ "hydra:SupportedProperty" , "hydra:IriTemplateMapping" ], "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:required" , "@type" : "rdf:Property" , "label" : "required" , "comment" : "True if the property is required, false otherwise." , "range" : "xsd:boolean" , "domainIncludes" : [ "hydra:SupportedProperty" , "hydra:IriTemplateMapping" ], "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:readable" , "@type" : "rdf:Property" , "label" : "readable" , "comment" : "True if the client can retrieve the property's value, false otherwise." , "domain" : "hydra:SupportedProperty" , "range" : "xsd:boolean" , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:writable" , "@type" : "rdf:Property" , "label" : "writable" , "comment" : "True if the client can change the property's value, false otherwise." , "domain" : "hydra:SupportedProperty" , "range" : "xsd:boolean" , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:writeable" , "subPropertyOf" : "hydra:writable" , "label" : "writable" , "comment" : "This property is left for compatibility purposes and hydra:writable should be used instead." , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "archaic" }, { "@id" : "hydra:supportedOperation" , "@type" : "hydra:Link" , "label" : "supported operation" , "comment" : "An operation supported by instances of the specific Hydra class, or the target of the Hydra link, or Iri template." , "range" : "hydra:Operation" , "domainIncludes" : [ "rdfs:Class" , "hydra:Class" , "hydra:Link" , "hydra:TemplatedLink" , "hydra:SupportedProperty" ], "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:operation" , "@type" : "hydra:Link" , "label" : "operation" , "comment" : "An operation supported by the Hydra resource." , "domain" : "hydra:Resource" , "range" : "hydra:Operation" , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:Operation" , "@type" : "hydra:Class" , "label" : "Operation" , "comment" : "An operation." , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:method" , "@type" : "rdf:Property" , "label" : "method" , "comment" : "The protocol method." , "domainIncludes" : [ "hydra:Operation" , "hydra:RetractedOperationSpecification" ], "range" : "xsd:string" , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:expects" , "@type" : "hydra:Link" , "label" : "expects" , "comment" : "The information expected by the Web API." , "domainIncludes" : [ "hydra:Operation" , "hydra:RetractedOperationSpecification" ], "rangeIncludes" : [ "rdfs:Resource" , "hydra:Resource" , "rdfs:Class" , "hydra:Class" ], "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:returns" , "@type" : "hydra:Link" , "label" : "returns" , "comment" : "The information returned by the Web API on success." , "domainIncludes" : [ "hydra:Operation" , "hydra:RetractedOperationSpecification" ], "rangeIncludes" : [ "rdfs:Resource" , "hydra:Resource" , "rdfs:Class" , "hydra:Class" ], "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:Status" , "@type" : "hydra:Class" , "label" : "Status code description" , "comment" : "Additional information about a status code that might be returned." , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:statusCode" , "@type" : "rdf:Property" , "label" : "status code" , "comment" : "The response status code. Please note it may happen this value will be different to actual status code received." , "domain" : "hydra:Status" , "range" : "xsd:integer" , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:title" , "@type" : "rdf:Property" , "subPropertyOf" : "rdfs:label" , "label" : "title" , "comment" : "A title, often used along with a description." , "range" : "xsd:string" , "domainIncludes" : [ "hydra:ApiDocumentation" , "hydra:Status" , "hydra:Class" , "hydra:SupportedProperty" , "hydra:Operation" , "hydra:Link" , "hydra:TemplatedLink" ], "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:description" , "@type" : "rdf:Property" , "subPropertyOf" : "rdfs:comment" , "label" : "description" , "comment" : "A description." , "range" : "xsd:string" , "domainIncludes" : [ "hydra:ApiDocumentation" , "hydra:Status" , "hydra:Class" , "hydra:SupportedProperty" , "hydra:Operation" , "hydra:Link" , "hydra:TemplatedLink" ], "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:Error" , "@type" : "hydra:Class" , "subClassOf" : "hydra:Status" , "label" : "Error" , "comment" : "A runtime error, used to report information beyond the returned status code." , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:Collection" , "@type" : "hydra:Class" , "subClassOf" : "hydra:Resource" , "label" : "Collection" , "comment" : "A collection holding references to a number of related resources." , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:collection" , "@type" : "hydra:Link" , "label" : "collection" , "comment" : "Collections somehow related to this resource." , "range" : "hydra:Collection" , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:memberAssertion" , "label" : "member assertion" , "comment" : "Semantics of each member provided by the collection." , "domainIncludes" : [ "hydra:Collection" , "hydra:Class" ], "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:manages" , "subPropertyOf" : "hydra:memberAssertion" , "label" : "manages" , "comment" : "This predicate is left for compatibility purposes and hydra:memberAssertion should be used instead." , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "archaic" }, { "@id" : "hydra:subject" , "label" : "subject" , "comment" : "The subject." , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:object" , "label" : "object" , "comment" : "The object." , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:member" , "@type" : "hydra:Link" , "label" : "member" , "comment" : "A member of the collection." , "domain" : "hydra:Collection" , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:view" , "@type" : "hydra:Link" , "label" : "view" , "comment" : "A specific view of a resource." , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:PartialCollectionView" , "@type" : "hydra:Class" , "subClassOf" : "hydra:Resource" , "label" : "PartialCollectionView" , "comment" : "A PartialCollectionView describes a partial view of a Collection. Multiple PartialCollectionViews can be connected with the next/previous properties to allow a client to retrieve all members of the collection." , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:totalItems" , "@type" : "rdf:Property" , "label" : "total items" , "comment" : "The total number of items referenced by a collection." , "domain" : "hydra:Collection" , "range" : "xsd:integer" , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:first" , "@type" : "hydra:Link" , "label" : "first" , "comment" : "The first resource of an interlinked set of resources." , "domain" : "hydra:Resource" , "range" : "hydra:Resource" , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:last" , "@type" : "hydra:Link" , "label" : "last" , "comment" : "The last resource of an interlinked set of resources." , "domain" : "hydra:Resource" , "range" : "hydra:Resource" , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:next" , "@type" : "hydra:Link" , "label" : "next" , "comment" : "The resource following the current instance in an interlinked set of resources." , "domain" : "hydra:Resource" , "range" : "hydra:Resource" , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:previous" , "@type" : "hydra:Link" , "label" : "previous" , "comment" : "The resource preceding the current instance in an interlinked set of resources." , "domain" : "hydra:Resource" , "range" : "hydra:Resource" , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:search" , "@type" : "hydra:TemplatedLink" , "label" : "search" , "comment" : "A Iri template that can be used to query a collection." , "range" : "hydra:IriTemplate" , "domain" : "hydra:Resource" , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:freetextQuery" , "@type" : "rdf:Property" , "label" : "freetext query" , "comment" : "A property representing a freetext query." , "range" : "xsd:string" , "domain" : "hydra:Resource" , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:TemplatedLink" , "@type" : "hydra:Class" , "subClassOf" : [ "hydra:Resource" , "rdf:Property" ], "label" : "Templated Link" , "comment" : "A templated link." , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:IriTemplate" , "@type" : "hydra:Class" , "label" : "IRI Template" , "comment" : "The class of IRI templates." , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:template" , "@type" : "rdf:Property" , "label" : "template" , "comment" : "A templated string with placeholders. The literal's datatype indicates the template syntax; if not specified, hydra:Rfc6570Template is assumed." , "seeAlso" : "hydra:Rfc6570Template" , "domain" : "hydra:IriTemplate" , "range" : "hydra:Rfc6570Template" , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:Rfc6570Template" , "@type" : "rdfs:Datatype" , "label" : "RFC6570 IRI template" , "comment" : "An IRI template as defined by RFC6570." , "seeAlso" : "http://tools.ietf.org/html/rfc6570" , "range" : "xsd:string" , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:variableRepresentation" , "@type" : "rdf:Property" , "label" : "variable representation" , "comment" : "The representation format to use when expanding the Iri template." , "range" : "hydra:VariableRepresentation" , "domainIncludes" : [ "hydra:IriTemplateMapping" , "hydra:IriTemplate" ], "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:VariableRepresentation" , "@type" : "hydra:Class" , "label" : "VariableRepresentation" , "comment" : "A representation specifies how to serialize variable values into strings." , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:BasicRepresentation" , "@type" : "hydra:VariableRepresentation" , "label" : "BasicRepresentation" , "comment" : "A representation that serializes just the lexical form of a variable value, but omits language and type information." , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:ExplicitRepresentation" , "@type" : "hydra:VariableRepresentation" , "label" : "ExplicitRepresentation" , "comment" : "A representation that serializes a variable value including its language and type information and thus differentiating between IRIs and literals." , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:mapping" , "@type" : "rdf:Property" , "label" : "mapping" , "comment" : "A variable-to-property mapping of the IRI template." , "domain" : "hydra:IriTemplate" , "range" : "hydra:IriTemplateMapping" , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:IriTemplateMapping" , "@type" : "hydra:Class" , "label" : "IriTemplateMapping" , "comment" : "A mapping from an IRI template variable to a property." , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:variable" , "@type" : "rdf:Property" , "label" : "variable" , "comment" : "An Iri template variable." , "domain" : "hydra:IriTemplateMapping" , "range" : "xsd:string" , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:resolveRelativeUsing" , "@type" : "rdf:Property" , "label" : "relative Uri resolution" , "comment" : "Instructs on how to resolve relative Uri created by the Iri template resolution." , "domain" : "hydra:IriTemplate" , "range" : "hydra:BaseUriSource" , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:BaseUriSource" , "@type" : "hydra:Class" , "subClassOf" : "hydra:Resource" , "label" : "Base Uri source" , "comment" : "Provides a base abstract for base Uri source for Iri template resolution." , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:Rfc3986" , "@type" : "hydra:BaseUriSource" , "label" : "RFC 3986 based" , "comment" : "States that the base Uri should be established using RFC 3986 reference resolution algorithm specified in section 5." , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:LinkContext" , "@type" : "hydra:BaseUriSource" , "label" : "Link context" , "comment" : "States that the link's context IRI, as defined in RFC 5988, should be used as the base Uri." , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:offset" , "@type" : "rdf:Property" , "label" : "skip" , "comment" : "Instructs to skip N elements of the set." , "range" : "xsd:nonNegativeInteger" , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:limit" , "@type" : "rdf:Property" , "label" : "take" , "comment" : "Instructs to limit set only to N elements." , "range" : "xsd:nonNegativeInteger" , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:pageIndex" , "@type" : "rdf:Property" , "subPropertyOf" : "hydra:pageReference" , "label" : "page index" , "comment" : "Instructs to provide a specific page of the collection at a given index." , "range" : "xsd:nonNegativeInteger" , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:pageReference" , "@type" : "rdf:Property" , "label" : "page reference" , "comment" : "Instructs to provide a specific page reference of the collection." , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:returnsHeader" , "@type" : "rdf:Property" , "label" : "returns header" , "comment" : "Name of the header returned by the operation." , "domain" : "hydra:Operation" , "rangeIncludes" : [ "xsd:string" , "hydra:HeaderSpecification" ], "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:expectsHeader" , "@type" : "rdf:Property" , "label" : "expects header" , "comment" : "Specification of the header expected by the operation." , "domain" : "hydra:Operation" , "rangeIncludes" : [ "xsd:string" , "hydra:HeaderSpecification" ], "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:HeaderSpecification" , "@type" : "rdfs:Class" , "subClassOf" : "hydra:Resource" , "label" : "Header specification" , "comment" : "Specifies a possible either expected or returned header values." , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:headerName" , "@type" : "rdf:Property" , "label" : "header name" , "comment" : "Name of the header." , "domain" : "hydra:HeaderSpecification" , "range" : "xsd:string" , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:possibleValue" , "@type" : "rdf:Property" , "label" : "possible header value" , "comment" : "Possible value of the header." , "domain" : "hydra:HeaderSpecification" , "range" : "xsd:string" , "vs:term_status" : "testing" }, { "@id" : "hydra:closedSet" , "@type" : "rdf:Property" , "label" : "closed set" , "comment" : "Determines whether the provided set of header values is closed or not." , "domain" : "hydra:HeaderSpecification" , "range" : "xsd:boolean" , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" }, { "@id" : "hydra:extension" , "@type" : "rdf:Property" , "label" : "extension" , "comment" : "Hint on what kind of extensions are in use." , "domain" : "hydra:ApiDocumentation" , "isDefinedBy" : "http://www.w3.org/ns/hydra/core" , "vs:term_status" : "testing" } ] }
12. The Hydra error context
+Note: This section is non-normative.
++{ "@context" : { "rdf" : "http://www.w3.org/1999/02/22-rdf-syntax-ns#" , "rdfs" : "http://www.w3.org/2000/01/rdf-schema#" , "hydra" : "http://www.w3.org/ns/hydra/core#" , "type" : { "@id" : "rdf:type" , "@type" : "@id" }, "title" : "rdfs:label" , "detail" : "rdfs:comment" , "status" : "hydra:statusCode" , "instance" : { "@id" : "rdfs:seeAlso" , "@type" : "@id" } } }