LinkedPipes DCAT-AP Viewer

This is a native DCAT-AP 2.0.1 catalog viewer. It is originally developed for OpenData.cz projects, however, it is completely open-source and resuable. It addresses the most painful disadvantages of CKAN when it comes to representing DCAT compatible data such as

• native DCAT-AP 2.0.1 input
• handles large numbers of distributions of a single dataset
• handles licenses attached to distributions
• supports EU Vocabularies codelists

Requirements

• Node.js (not 15 ATM) & npm
• OpenJDK for Apache Solr, if not dockerized
• Apache Solr 8.7 (Docker)
• Apache CouchDB 2.3 and up (Docker)

Requirements for data preparation

• LinkedPipes ETL, the preparation pipeline and the codelist pipeline

Installation

Install Solr or run in it Docker. It will contain the search index. For installation, you may proceed like this:

• Download Apache Solr - e.g. solr-8.7.0.tgz
• Extract the service installer tar xzf solr-8.7.0.tgz solr-8.7.0/bin/install_solr_service.sh --strip-components=2
• Run the service installer sudo bash ./install_solr_service.sh solr-8.7.0.tgz

Next, configure Solr like this:

• Create Solr core sudo -u solr /opt/solr/bin/solr create -c dcat-ap-viewer

• Add following to dcat-ap-viewer/conf/solrconfig.xml file (adjust the version numbers as necessary) and restart Solr.

  <lib path="${solr.install.dir:../../../..}/dist/solr-analysis-extras-8.7.0.jar" />  
  <lib path="${solr.install.dir:../../../..}/contrib/analysis-extras/lib/icu4j-62.1.jar" />  
  <lib path="${solr.install.dir:../../../..}/contrib/analysis-extras/lucene-libs/lucene-analyzers-icu-8.7.0.jar" />

• Prepare Solr schema (change locale to your language, the example bellow is for cs and en):

curl http://localhost:8983/solr/dcat-ap-viewer/schema -X POST -H 'Content-type:application/json' --data-binary '{
    "add-field-type" : {
        "name" : "ascii_string",
        "class" : "solr.TextField",
        "positionIncrementGap" : "100",
        "analyzer" : {
            "tokenizer" : { "class" : "solr.WhitespaceTokenizerFactory" },
            "filters" : [
                { 
                    "class" : "solr.LowerCaseFilterFactory" 
                }, { 
                    "class" : "solr.ASCIIFoldingFilterFactory",
                    "preserveOriginal" : "false" 
                }
            ]
        }
    },
    "add-field-type" : {
        "name" : "string_icu_cs",
        "class" : "org.apache.solr.schema.ICUCollationField",
        "locale": "cs",
        "strength" : "primary"
    },    
    "add-field-type" : {
        "name" : "string_icu_en",
        "class" : "org.apache.solr.schema.ICUCollationField",
        "locale": "en",
        "strength" : "primary"
    },
    "add-field" : { "name" : "iri", "type" : "string" , "indexed" : false, "multiValued" : false },
    "add-field" : { "name" : "modified", "type" : "pdate", "multiValued" : false},
    "add-field" : { "name" : "issued", "type" : "pdate", "multiValued" : false },
    "add-field" : { "name" : "accrual_periodicity", "type" : "string", "multiValued" : false },
    "add-field" : { "name" : "publisher", "type" : "string" , "indexed" : true, "multiValued" : false },
    "add-field" : { "name" : "file_type", "type" : "strings", "indexed" : true },
    "add-field" : { "name" : "license", "type" : "strings", "indexed" : true },
    "add-field" : { "name" : "theme", "type" : "strings" },
    "add-field" : { "name" : "temporal_start", "type" : "pdate", "docValues" : true, "multiValued" : false },
    "add-field" : { "name" : "temporal_end", "type" : "pdate", "docValues" : true, "multiValued" : false },
    "add-field" : { "name" : "spatial", "type" : "strings" },
    "add-field" : { "name" : "is_part_of", "type" : "string" , "indexed" : true, "multiValued" : false },
    "add-field" : { "name" : "data_service_type", "type" : "strings", "indexed" : true },

    "add-field" : { "name" : "description_cs", "type" : "string", "multiValued" : false },
    "add-field" : { "name" : "keyword_cs", "type" : "strings" },
    "add-field" : { "name" : "title_cs", "type" : "string", "multiValued" : false },
    "add-field" : { "name" : "title_cs_sort", "type" : "string_icu_cs", "docValues" : true, "multiValued" : false },
    "add-field" : { "name" : "title_cs_query", "type" : "ascii_string", "multiValued" : false },
    "add-copy-field" : { "source" : "title_cs_sort", "dest" : "title_cs_query" },

    "add-field" : { "name" : "description_en", "type" : "string", "multiValued" : false },
    "add-field" : { "name" : "keyword_en", "type" : "strings" },
    "add-field" : { "name" : "title_en", "type" : "string", "multiValued" : false },
    "add-field" : { "name" : "title_en_sort", "type" : "string_icu_en", "docValues" : true, "multiValued" : false },
    "add-field" : { "name" : "title_en_query", "type" : "ascii_string", "multiValued" : false },
    "add-copy-field" : { "source" : "title_en_sort", "dest" : "title_en_query" },

    "add-field" : { "name" : "vdf_codelist", "type" : "boolean", "multiValued" : false },
    "add-field" : { "name" : "vdf_public_data", "type" : "boolean", "multiValued" : false },    

    "replace-field" : { "name": "_text_", "type" : "ascii_string", "multiValued" : true, "indexed" : true, "stored" : false },
    "add-copy-field" : { "source" : "title_cs", "dest" : "_text_" },
    "add-copy-field" : { "source" : "title_en", "dest" : "_text_" },
    "add-copy-field" : { "source" : "description_cs", "dest" : "_text_" },
    "add-copy-field" : { "source" : "description_en", "dest" : "_text_" },
    "add-copy-field" : { "source" : "keyword_cs", "dest" : "_text_" },
    "add-copy-field" : { "source" : "keyword_en", "dest" : "_text_" }    
}'

• And then:

curl http://localhost:8983/solr/dcat-ap-viewer/config -H 'Content-type:application/json' -d'{
    "set-property" : {"requestDispatcher.requestParsers.enableRemoteStreaming":true},
    "set-property" : {"requestDispatcher.requestParsers.enableStreamBody":true}
}'

Install Apache CouchDB, e.g. via a package manager, or run it in Docker. It will contain the datasets, distributions and, optionally, the code list labels.

Install LinkedPipes DCAT-AP viewer

• Clone the repository
• Install dependencies:

npm install

• Copy and edit the configuration file: cp configuration-example.yaml configuration.yaml Please refer to the profile of your choice, client/profile-lkod or client/profile-nkod , for more information about the configuration.

Load the data

• Install LinkedPipes ETL and import, configure and run the preparation pipeline. It has the DCAT-AP catalog (its RDF representation) on the input, this is where you provide your DCAT-AP dump. The pipeline assumes that Solr is running on localhost:8983 and CouchDB is running on localhost:5984.
• To enable support for the European Metadata Registry Named Authority Lists (EU MDR NALs) linked from DCAT-AP records, configure and run the codelist pipeline. It will populate the Apache CouchDB instance with the codelists.

Running DCAT-AP Viewer

Before the first run the DCAT-AP Viewer client javascript needs to be compiled using command:

npm run build

After the compilation is done the following command can be used to start the server:

npm run start