Better to explicitly state stepId must be mandatory within a workfl…

…ow (#134)

versions/1.0.0.md

@@ -321,7 +321,7 @@ Describes a single workflow step which MAY be a call to an API operation ([OpenA
 Field Name | Type | Description
 ---|:---:|---
 <a name="stepDescription"></a>description | `string` | A description of the step. [CommonMark syntax](https://spec.commonmark.org/) MAY be used for rich text representation.
-<a name="stepId"></a>stepId | `string` | **REQUIRED**. Unique string to represent the step. The id SHOULD be unique amongst all steps described in the workflow. The stepId value is **case-sensitive**. Tools and libraries MAY use the stepId to uniquely identify a workflow step, therefore, it is RECOMMENDED to follow common programming naming conventions. SHOULD conform to the regular expression `[A-Za-z0-9_\-]+`.
+<a name="stepId"></a>stepId | `string` | **REQUIRED**. Unique string to represent the step. The `stepId` MUST be unique amongst all steps described in the workflow. The `stepId` value is **case-sensitive**. Tools and libraries MAY use the `stepId` to uniquely identify a workflow step, therefore, it is RECOMMENDED to follow common programming naming conventions. SHOULD conform to the regular expression `[A-Za-z0-9_\-]+`.
 <a name="stepOperationId"></a>operationId | `string` | The name of an existing, resolvable operation, as defined with a unique `operationId` and existing within one of the `sourceDescriptions`. The referenced operation will be invoked by this workflow step. If multiple (non `workflowsSpec` type) `sourceDescriptions` are defined, then the `operationId` MUST be specified using a [runtime expression](#runtime-expressions) (e.g., `$sourceDescriptions.<name>.<operationId>`) to avoid ambiguity or potential clashes. This field is mutually exclusive of the `operationRef` and `workflowId` fields respectively.
 <a name="stepOperationRef"></a>operationRef | `string` | A relative or absolute URI reference to an OAS operation. This field is mutually exclusive of the `operationId` and `workflowId` fields respectively. A complete [URI Template](https://www.rfc-editor.org/rfc/rfc6570) SHOULD be used. The operation being referenced MUST be described within one of the `source` descriptions. 
 <a name="stepWorkflowId"></a>workflowId | `string` | The [workflowId](#fixed-fields-2) referencing an existing workflow within the Workflows Description. If multiple `workflowsSpec` type `sourceDescriptions` are defined, then the `workflowId` MUST be specified using a [runtime expression](#runtime-expressions) (e.g., `$sourceDescriptions.<name>.<workflowId>`) to avoid ambiguity or potential clashes. The field is mutually exclusive of the `operationId` and `operationRef` fields respectively.