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Workflows Specification

Version 1.0.0-prerelease

Work is progressing well on this specification. Formally, we are still in a prerelease status

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 RFC2119 RFC8174 when, and only when, they appear in all capitals, as shown here.

This document is licensed under The Apache License, Version 2.0.

Introduction

Being able to express specific sequences of calls and articulate the dependencies between them to achieve a particular goal is desirable in the context of API descriptions. The aim of the Workflows Specification is to provide a mechanism that can define sequences of calls and their dependencies to be expressed in the context of delivering a particular outcome or set of outcomes when dealing with API descriptions (such as OpenAPI descriptions).

The Workflows Specification can articulate these workflows in a human-readable and machine-readable manner, thus improving the capability of API specifications to tell the story of the API in a manner that can improve the consuming developer experience.

Table of Contents

Definitions

Workflows Description

A self-contained document (or set of documents) which defines or describes API workflows (specific sequence of calls to achieve a particular goal in the context of an API definition). A Workflows Description (WD) uses and conforms to the Workflows Specification, and MUST contain a valid Workflows Specification version field (workflowsSpec), an Info field, a sourceDescriptions field with at least one defined Source, and there MUST be at least one Workflow defined in the workflows fixed field.

Specification

Versions

The Workflows Specification is versioned using a major.minor.patch versioning scheme. The major.minor portion of the version string (for example 1.0) SHALL designate the Workflows feature set. .patch versions address errors in, or provide clarifications to, this document, not the feature set. The patch version SHOULD NOT be considered by tooling, making no distinction between 1.0.0 and 1.0.1 for example.

Format

A Workflows Description that conforms to the Workflows Specification is itself a JSON object, which may be represented either in JSON or YAML format.

All field names in the specification are case sensitive. This includes all fields that are used as keys in a map, except where explicitly noted that keys are case insensitive.

In order to preserve the ability to round-trip between YAML and JSON formats, YAML version 1.2 is RECOMMENDED along with some additional constraints:

Workflows Description Structure

It is RECOMMENDED that the entry Workflows document be named: workflows.json or workflows.yaml.

A Workflows Description MAY be made up of a single document or be divided into multiple, connected parts at the discretion of the author. If workflows from other documents are being referenced, they must by included as a Source Description Object. In a multi-document description, the document containing the Workflows Specification Object is known as the entry Workflows document.

Data Types

Data types in the Workflows Specification are based on the types supported by the JSON Schema Specification Draft 2020-12. Note that integer as a type is also supported and is defined as a JSON number without a fraction or exponent part.

As defined by the JSON Schema Validation vocabulary, data types can have an optional modifier property: format. Workflows additionally supports the formats (similar to the OpenAPI specification) to provide fine detail for primitive data types.

The formats defined are:

type format Comments
integer int32 signed 32 bits
integer int64 signed 64 bits (a.k.a long)
number float
number double
string password A hint to UIs to obscure input.

Relative References in URLs

Unless specified otherwise, all properties that are URLs MAY be relative references as defined by RFC3986. Unless specified otherwise, relative references are resolved using the URL of the referring document.

Schema

In the following description, if a field is not explicitly REQUIRED or described with a MUST or SHALL, it can be considered OPTIONAL.

Workflows Specification Object

This is the root object of the Workflows Description.

Fixed Fields
Field Name Type Description
workflowsSpec string REQUIRED. This string MUST be the version number of the Workflows Specification that the Workflows Description uses. The workflowsSpec field MUST be used by tooling to interpret the Workflows Description.
info Info Object REQUIRED. Provides metadata about the Workflows. The metadata MAY be used by tooling as required.
sourceDescriptions [Source Description Object] REQUIRED. A list of source descriptions (such as an OpenAPI description) this workflow SHALL apply to. The list MUST have at least one entry.
workflows [Workflow Object] REQUIRED. A list of workflows. The list MUST have at least one entry.
components Components Object An element to hold various schemas for the Workflows Description.

This object MAY be extended with Specification Extensions.

Workflows Specification Object Example
workflowsSpec: 1.0.0-prerelease
info:
  title: A pet purchasing workflow
  summary: This workflow showcases how to purchase a pet through a sequence of API calls
  description: |
      This workflow walks you through the steps of `searching` for, `selecting`, and `purchasing` an available pet.
  version: 1.0.1
sourceDescriptions:
- name: petStoreDescription
  url: https://github.com/swagger-api/swagger-petstore/blob/master/src/main/resources/openapi.yaml
  type: openapi

workflows:
- workflowId: loginUserAndRetrievePet
  summary: Login User and then retrieve pets
  description: This workflow lays out the steps to login a user and then retrieve pets
  inputs:
      type: object
      properties:
          username:
              type: string
          password:
              type: string
  steps:
  - stepId: loginStep
    description: This step demonstrates the user login step
    operationId: loginUser
    parameters:
      # parameters to inject into the loginUser operation (parameter name must be resolvable at the referenced operation and the value is determined using {expression} syntax)
      - name: username
        in: query
        value: $inputs.username
      - name: password
        in: query
        value: $inputs.password
    successCriteria:
      # assertions to determine step was successful
      - condition: $statusCode == 200
    outputs:
      # outputs from this step
      tokenExpires: $response.header.X-Expires-After
      rateLimit: $response.header.X-Rate-Limit
      sessionToken: $response.body
  - stepId: getPetStep
    description: retrieve a pet by status from the GET pets endpoint
    operationPath: '{$sourceDescriptions.petstoreDescription.url}#/paths/~1pet~1findByStatus/get'
    parameters:
      - name: status
        in: query
        value: 'available'
      - name: Authorization
        in: header
        value: $steps.loginUser.outputs.sessionToken
    successCriteria:
      - condition: $statusCode == 200
    outputs:
      # outputs from this step
      availablePets: $response.body
  outputs:
      available: $steps.getPetStep.availablePets

Info Object

The object provides metadata about the API Workflows defined in this document. The metadata MAY be used by the clients if needed.

Fixed Fields
Field Name Type Description
title string REQUIRED. A human readable title of the Workflows Description.
summary string A short summary of the Workflows Description.
description string A description of the purpose of the workflows defined. CommonMark syntax MAY be used for rich text representation.
version string REQUIRED. The version identifier of the Workflows document (which is distinct from the Workflows Specification version.

This object MAY be extended with Specification Extensions.

Info Object Example
title: A pet purchasing workflow
summary: This workflow showcases how to purchase a pet through a sequence of API calls
description: |
    This workflow walks you through the steps of searching for, selecting, and purchasing an available pet.
version: 1.0.1

Source Description Object

Describes a source description (such as an OpenAPI description) that will be referenced by one or more workflows described within a Workflows Description.

An object storing a map between named description keys and location URLs to the source descriptions (such as an OpenAPI description) this workflow SHALL apply to. Each source location string MUST be in the form of a URI-reference as defined by RFC3986 section 4.1.

Fixed Fields
Field Name Type Description
name string REQUIRED. A unique name for the source description. Tools and libraries MAY use the name to uniquely identify a source description, therefore, it is RECOMMENDED to follow common programming naming conventions. SHOULD conform to the regular expression [A-Za-z0-9_\-]+.
url string REQUIRED. A URL to a source description to be used by a Workflow. If a relative reference is used, it MUST be in the form of a URI-reference as defined by RFC3986 section 4.2.
type string The type of source description. Possible values are "openapi" or "workflowsSpec".

This object MAY be extended with Specification Extensions.

Source Description Object Example
name: petStoreDescription
url: https://github.com/swagger-api/swagger-petstore/blob/master/src/main/resources/openapi.yaml
type: openapi

Workflow Object

Describes the steps to be taken across one or more APIs to achieve an objective. The workflow object MAY define inputs needed in order to execute workflow steps, where the defined steps represent a call to an API operation or another workflow, and a set of outputs.

Fixed Fields
Field Name Type Description
workflowId string REQUIRED. Unique string to represent the workflow. The id MUST be unique amongst all workflows describe in the Workflows Description. The workflowId value is case-sensitive. Tools and libraries MAY use the workflowId to uniquely identify a workflow, therefore, it is RECOMMENDED to follow common programming naming conventions. SHOULD conform to the regular expression [A-Za-z0-9_\-]+.
summary string A summary of the purpose or objective of the workflow.
description string A description of the workflow. CommonMark syntax MAY be used for rich text representation.
inputs JSON Schema A JSON Schema 2020-12 object representing the input parameters used by this workflow.
dependsOn [string] A list of workflows that MUST be completed before this workflow can be processed. The values provided MUST be a workflowId. If the workflow depended on is defined within the current Workflow Document, then specify the workflowId of the relevant local workflow. If the workflow is defined in a separate Workflows Document then the workflow MUST be defined in the sourceDescriptions and the workflowId MUST be specified using a runtime expression (e.g., $sourceDescriptions.<name>.<workflowId>) to avoid ambiguity or potential clashes.
steps [Step Object] REQUIRED. An ordered list of steps where each step represents a call to an API operation or to another workflow.
successActions [Success Action Object | Reusable Object] A list of success actions that are applicable for all steps described under this workflow. These success actions can be overridden at the step level but cannot be removed there. If a Reusable Object is provided, it MUST link to success actions defined in the components/successActions of the current Workflows document. The list MUST NOT include duplicate success actions.
failureActions [Failure Action Object | Reusable Object] A list of failure actions that are applicable for all steps described under this workflow. These failure actions can be overridden at the step level but cannot be removed there. If a Reusable Object is provided, it MUST link to failure actions defined in the components/failureActions of the current Workflows document. The list MUST NOT include duplicate failure actions.
outputs Map[string, {expression}] A map between a friendly name and a dynamic output value. The name MUST use keys that match the regular expression: ^[a-zA-Z0-9\.\-_]+$.
parameters [Parameter Object | Reusable Object] A list of parameters that are applicable for all steps described under this workflow. These parameters can be overridden at the step level but cannot be removed there. Each parameter MUST be passed to an operation or workflow as referenced by operationId, operationPath, or workflowId as specified within each step. If a Reusable Object is provided, it MUST link to a parameter defined in the components/parameters of the current Workflows document. The list MUST NOT include duplicate parameters.

This object MAY be extended with Specification Extensions.

Workflow Object Example
workflowId: loginUser
summary: Login User
description: This workflow lays out the steps to login a user
inputs:
    type: object
    properties:
        username:
            type: string
        password:
            type: string
steps:
  - stepId: loginStep
    description: This step demonstrates the user login step
    operationId: loginUser
    parameters:
      # parameters to inject into the loginUser operation (parameter name must be resolvable at the referenced operation and the value is determined using {expression} syntax)
      - name: username
        in: query
        value: $inputs.username
      - name: password
        in: query
        value: $inputs.password
    successCriteria:
        # assertions to determine step was successful 
        - condition: $statusCode == 200
    outputs:
        # outputs from this step
        tokenExpires: $response.header.X-Expires-After
        rateLimit: $response.header.X-Rate-Limit
outputs:
    tokenExpires: $steps.loginStep.outputs.tokenExpires

Step Object

Describes a single workflow step which MAY be a call to an API operation (OpenAPI Operation Object or another Workflow Object.

Fixed Fields
Field Name Type Description
description string A description of the step. CommonMark syntax MAY be used for rich text representation.
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_\-]+.
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 (e.g., $sourceDescriptions.<name>.<operationId>) to avoid ambiguity or potential clashes. This field is mutually exclusive of the operationPath and workflowId fields respectively.
operationPath string A reference to a Source combined with a JSON Pointer to reference an operation. This field is mutually exclusive of the operationId and workflowId fields respectively. The operation being referenced MUST be described within one of the sourceDescriptions descriptions. A runtime expression syntax MUST be used to identify the source description document. If the referenced operation has an operationId defined then the operationId SHOULD be preferred over the operationPath.
workflowId string The workflowId 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 (e.g., $sourceDescriptions.<name>.<workflowId>) to avoid ambiguity or potential clashes. The field is mutually exclusive of the operationId and operationPath fields respectively.
parameters [Parameter Object | Reusable Object] A list of parameters that MUST be passed to an operation or workflow as referenced by operationId, operationPath, or workflowId. If a parameter is already defined at the Workflow, the new definition will override it but can never remove it. If a Reusable Object is provided, it MUST link to a parameter defined in the components/parameters of the current Workflows document. The list MUST NOT include duplicate parameters.
requestBody Request Body Object The request body to pass to an operation as referenced by operationId or operationPath. The requestBody is fully supported in HTTP methods where the HTTP 1.1 specification RFC7231 has explicitly defined semantics for request bodies. In other cases where the HTTP spec is vague (such as GET, HEAD and DELETE), requestBody is permitted but does not have well-defined semantics and SHOULD be avoided if possible.
successCriteria [Criterion Object] A list of assertions to determine the success of the step. Each assertion is described using a Criterion Object. All assertions MUST be satisfied for the step to be deemed successful.
onSuccess [Success Action Object | Reusable Object] An array of success action objects that specify what to do upon step success. If omitted, the next sequential step shall be executed as the default behavior. If multiple success actions have similar criteria, the first sequential action matching the criteria SHALL be the action executed. If a success action is already defined at the Workflow, the new definition will override it but can never remove it. If a Reusable Object is provided, it MUST link to a success action defined in the components of the current Workflows document. The list MUST NOT include duplicate success actions.
onFailure [Failure Action Object | Reusable Object] An array of failure action objects that specify what to do upon step failure. If omitted, the default behavior is to break and return. If multiple failure actions have similar criteria, the first sequential action matching the criteria SHALL be the action executed. If a failure action is already defined at the Workflow, the new definition will override it but can never remove it. If a Reusable Object is provided, it MUST link to a failure action defined in the components of the current Workflows document. The list MUST NOT include duplicate failure actions.
outputs Map[string, {expression}] A map between a friendly name and a dynamic output value defined using a runtime expression. The name MUST use keys that match the regular expression: ^[a-zA-Z0-9\.\-_]+$.

This object MAY be extended with Specification Extensions.

Step Object Example

Single step

stepId: loginStep
description: This step demonstrates the user login step
operationId: loginUser
parameters:
    # parameters to inject into the loginUser operation (parameter name must be resolvable at the referenced operation and the value is determined using {expression} syntax)
    - name: username
      in: query
      value: $inputs.username
    - name: password
      in: query
      value: $inputs.password
successCriteria:
    # assertions to determine step was successful
    - condition: $statusCode == 200
outputs:
    # outputs from this step
    tokenExpires: $response.header.X-Expires-After
    rateLimit: $response.header.X-Rate-Limit

Multiple steps

steps:
  - stepId: loginStep
    description: This step demonstrates the user login step
    operationId: loginUser
    parameters:
        # parameters to inject into the loginUser operation (parameter name must be resolvable at the referenced operation and the value is determined using {expression} syntax)
      - name: username
        in: query
        value: $inputs.username
      - name: password
        in: query
        value: $inputs.password
    successCriteria:
        # assertions to determine step was successful
      - condition: $statusCode == 200
    outputs:
        # outputs from this step
        tokenExpires: $response.header.X-Expires-After
        rateLimit: $response.header.X-Rate-Limit
        sessionToken: $response.body
  - stepId: getPetStep
    description: retrieve a pet by status from the GET pets endpoint
    operationPath: '{$sourceDescriptions.petStoreDescription.url}#/paths/~1pet~1findByStatus/get'
    parameters:
      - name: status
        in: query
        value: 'available'
      - name: Authorization
        in: header
        value: $steps.loginUser.outputs.sessionToken
    successCriteria:
      - condition: $statusCode == 200
    outputs:
        # outputs from this step
        availablePets: $response.body

Parameter Object

Describes a single step parameter. A unique parameter is defined by the combination of a name and in fields. There are four possible locations specified by the in field:

  • path - Used together with OpenAPI style Path Templating, where the parameter value is actually part of the operation's URL. This does not include the host or base path of the API. For example, in /items/{itemId}, the path parameter is itemId.
  • query - Parameters that are appended to the URL. For example, in /items?id=###, the query parameter is id.
  • header - Custom headers that are expected as part of the request. Note that RFC7230 states header names are case insensitive.
  • cookie - Used to pass a specific cookie value to the source API.
Fixed Fields
Field Name Type Description
name string REQUIRED. The name of the parameter. Parameter names are case sensitive.
in string The name location of the parameter. Possible values are "path", "query", "header", "cookie", or "body". When the step in context specifies a workflowId, then all parameters map to workflow inputs. In all other scenarios (e.g., a step specifies an operationId), the in field MUST be specified.
value Any | {expression} REQUIRED. The value to pass in the parameter. The value can be a constant or an Runtime Expression to be evaluated and passed to the referenced operation or workflow.

This object MAY be extended with Specification Extensions.

Parameter Object Example

Query Example

- name: username
  in: query
  value: $inputs.username

Header Example

- name: X-Api-Key
  in: header
  value: $inputs.x-api-key

Success Action Object

A single success action which describes an action to take upon success of a workflow step. There are two possible values for the type field.

  • end - The workflow ends, and context returns to the caller with applicable outputs
  • goto - A one-way transfer of workflow control to the specified label (either a workflowId or stepId)
Fixed Fields
Field Name Type Description
name string REQUIRED. The name of the success action. Names are case sensitive.
type string REQUIRED. The type of action to take. Possible values are "end" or "goto".
workflowId string The workflowId referencing an existing workflow within the Workflows Description to transfer to upon success of the step. This field is only relevant when the type field value is "goto". If multiple workflowsSpec type sourceDescriptions are defined, then the workflowId MUST be specified using a runtime expression (e.g., $sourceDescriptions.<name>.<workflowId>) to avoid ambiguity or potential clashes. This field is mutually exclusive to stepId.
stepId string The stepId to transfer to upon success of the step. This field is only relevant when the type field value is "goto". The referenced stepId MUST be within the current workflow. This field is mutually exclusive to workflowId.
criteria [Criterion Object] A list of assertions to determine if this action SHALL be executed. Each assertion is described using a Criterion Object. All criteria assertions MUST be satisfied for the action to be executed.

This object MAY be extended with Specification Extensions.

Success Action Object Example
name: JoinWaitingList
type: goto
stepId: joinWaitingListStep
criteria:
    # assertions to determine if this success action should be executed
    - context: $response.body
      condition: $[?count(@.pets) > 0]
      type: JSONPath

Failure Action Object

A single failure action which describes an action to take upon failure of a workflow step. There are three possible values for the type field.

  • end - The workflow ends, and context returns to the caller with applicable outputs
  • retry - The current step will be retried. The retry will be constrained by the retryAfter and retryLimit fields. If a stepId or workflowId are specified, then the reference is executed and the context is returned, after which the current step is retried.
  • goto - A one-way transfer of workflow control to the specified label (either a workflowId or stepId)
Fixed Fields
Field Name Type Description
name string REQUIRED. The name of the failure action. Names are case sensitive.
type string REQUIRED. The type of action to take. Possible values are "end", "retry", or "goto".
workflowId string The workflowId referencing an existing workflow within the Workflows Description to transfer to upon failure of the step. This field is only relevant when the type field value is "goto" or "retry". If multiple workflowsSpec type sourceDescriptions are defined, then the workflowId MUST be specified using a runtime expression (e.g., $sourceDescriptions.<name>.<workflowId>) to avoid ambiguity or potential clashes. This field is mutually exclusive to stepId. When used with "retry", context transfers back upon completion of the specified workflow.
stepId string The stepId to transfer to upon failure of the step. This field is only relevant when the type field value is "goto" or "retry". The referenced stepId MUST be within the current workflow. This field is mutually exclusive to workflowId. When used with "retry", context transfers back upon completion of the specified step.
retryAfter number A non-negative decimal indicating the seconds to delay after the step failure before another attempt SHALL be made. Note: if an HTTP Retry-After response header was returned to a step from a targeted operation, then it SHOULD overrule this particular field value. This field only applies when the type field value is "retry" or "function".
retryLimit integer A non-negative integer indicating how many attempts to retry the step MAY be attempted before failing the overall step. If not specified then a single retry SHALL be attempted. This field only applies when the type field value is "retry". The retryLimit MUST be exhausted prior to executing subsequent failure actions.
criteria [Criterion Object] A list of assertions to determine if this action SHALL be executed. Each assertion is described using a Criterion Object.

This object MAY be extended with Specification Extensions.

Failure Action Object Example
name: retryStep
type: retry
retryAfter: 1
retryLimit: 5
criteria:
    # assertions to determine if this action should be executed
    - condition: $statusCode == 503

Components Object

Holds a set of reusable objects for different aspects of the Workflows Specification. All objects defined within the components object will have no effect on the workflow unless they are explicitly referenced from properties outside the components object.

Components are scoped to the Workflows document they are defined in. For example, if a step defined in Workflows document "A" references a workflow defined in Workflows document "B", the components in "A" are not considered when evaluating the workflow referenced in "B".

Fixed Fields
Field Name Type Description
inputs Map[string, JSON Schema] An object to hold reusable JSON Schema objects to be referenced from workflow inputs.
parameters Map[string, Parameter Object] An object to hold reusable Parameter Objects
successActions Map[string, Success Action Object] An object to hold reusable Success Actions Objects.
failureActions Map[string, Failure Action Object] An object to hold reusable Failure Actions Objects.

This object MAY be extended with Specification Extensions.

All the fixed fields declared above are objects that MUST use keys that match the regular expression: ^[a-zA-Z0-9\.\-_]+$. The key is used to refer to the input or parameter in other parts of the Workflow Description.

Field Name Examples:

User
User_1
User_Name
user-name
my.org.User
Components Object Example
components:
  parameters:
    storeId:
      name: storeId
      in: header
      value: $inputs.x-store-id
  inputs:
    pagination:
      type: object
      properties:
        page:
          type: integer
          format: int32
        pageSize:
          type: integer
          format: int32
  failureActions:
    refreshToken:
      name: refreshExpiredToken
      type: retry
      retryAfter: 1
      retryLimit: 5
      workflowId: refreshTokenWorkflowId
      criteria:
          # assertions to determine if this action should be executed
          - condition: $statusCode == 401       
"components": {
  "parameters": {
    "storeId": {
      "name": "storeId",
      "in": "header",
      "value": "$inputs.x-store-id"
    }
  },
  "inputs": {
    "pagination": {
      "type": "object",
      "properties": {
        "page": {
          "type": "integer",
          "format": "int32"
        },
        "pageSize": {
          "type": "integer",
          "format": "int32"
        }
      }
    }
  },
  "failureActions": {
    "refreshToken": {
      "name": "refreshExpiredToken",
      "type": "retry",
      "retryAfter": 1,
      "retryLimit": 5,
      "workflowId": "refreshTokenWorkflowId",
      "criteria": [
        {
          "condition": "{$statusCode == 401}"
        }
      ]
    }
  }
}

Reusable Object

A simple object to allow referencing of objects contained within the Components Object. It can be used from locations within steps or workflows in the Workflows Description. Note - Input Objects MUST use standard JSON Schema referencing via the $ref keyword while all non JSON Schema objects use this object and its expression based referencing mechanism.

Fixed Fields
Field Name Type Description
value string Sets a value of the referenced parameter. This is only applicable for parameter object references.

This object cannot be extended with additional properties and any properties added MUST be ignored.

Reusable Object Example
  reference: $components.successActions.notify
  {
    "reference": "$components.successActions.notify"
  }
  reference: $components.parameters.page
  value: 1
  {
    "reference": "$components.parameters.page",
    "value": 1
  }

Criterion Object

An object used to specify the context, conditions, and condition types that can be used to prove or satisfy assertions specified in Step Object successCriteria, Success Action Object criteria, and Failure Action Object criteria.

There are three flavors of conditions supported:

  • simple - where basic literals, operators, and loose comparisons are used in combination with Runtime Expressions.
  • regex - where a regex pattern is applied on the supplied context. The context is defined by a Runtime Expression.
  • JSONPath - where a JSONPath expression is applied. The root node context is defined by a Runtime Expression.
Literals

As part of a condition expression, you can use boolean, null, number, or string data types.

Type Literal value
boolean true or false
null null
number Any number format supported in Data Types
string Strings MUST use single quotes (') around the string. To use a literal single quote, escape the literal single quote using an additional single quote ('').
Operators
Operator Description
< Less than
<= Less than or equal
> Greater than
>= Greater than or equal
== Equal
!= Not equal
! Not
&& And
|| Or
() Logical Grouping
[] Index (0-based)
. Property de-reference

String comparisons MUST be case insensitive.

Fixed Fields
Field Name Type Description
context {expression} A runtime expression used to set the context for the condition to be applied on. If type is specified, then the context MUST be provided (e.g. $response.body would set the context that a JSONPath query expression could be applied to).
condition string REQUIRED. The condition to apply. Conditions can be simple (e.g. $statusCode == 200 which applies a operator on a value obtained from a runtime expression), or a regex, or a JSONPath expression. For regex and JSONPath, the type and context MUST be specified.
type string | Criterion Expression Type Object The type of condition to be applied. If specified, the options allowed are simple, regex, jsonpath or xpath. If omitted, then the condition is assumed to be simple, which at most combines literals, operators and Runtime Expressions. If jsonpath, then the expression MUST conform to JSON Path. If xpath the expression MUST conform to XML Path Language 3.1. Should other variants of JSON Path or XPath be required, then a Criterion Expression Type Object MUST be specified.

This object MAY be extended with Specification Extensions.

Criterion Object Example

Simple Condition Example

- condition: $statusCode == 200

Regex Condition Example

- context: $statusCode
  condition: '^200$'
  type: regex

JSONPath Condition Example

- context: $response.body
  condition: $[?count(@.pets) > 0]
  type: jsonpath

Criterion Expression Type Object

An object used to describe the type and version of an expression used within a Criterion Object. If this object is not defined, then the following defaults apply:

Defining this object gives the ability to utilize tooling compatible with older versions of either JSON Path or XPath.

Fixed Fields
Field Name Type Description
type string REQUIRED. The type of condition to be applied. The options allowed are jsonpath or xpath.
version string REQUIRED. A short hand string representing the version of the expression type being used. The allowed values for JSON Path are draft-goessner-dispatch-jsonpath-00. The allowed values for XPath are xpath-30, xpath-20, or xpath-10.

This object MAY be extended with Specification Extensions.

Criterion Expression Type Example

JSON Path Example

  type: jsonpath
  version: draft-goessner-dispatch-jsonpath-00

XPath Example

  type: xpath
  version: xpath-30

Request Body Object

A single request body describing the Content-Type and request body content to be passed by a step to an operation.

Fixed Fields
Field Name Type Description
contentType string The Content-Type for the request content. If omitted then refer to Content-Type specified at the targeted operation to understand serialization requirements.
payload Any A value representing the request body payload. The value can be a literal value or can contain Runtime Expressions which MUST be evaluated prior to calling the referenced operation. To represent examples of media types that cannot be naturally represented in JSON or YAML, use a string value to contain the example, escaping where necessary.

replacements | [Payload Replacement Object] | A list of locations and values to set within a payload.

This object MAY be extended with Specification Extensions.

RequestBody Object Example

JSON Templated Example

 contentType: application/json
 payload: |
   {
     "petOrder": {
       "petId": "{$inputs.pet_id}",
       "couponCode": "{$inputs.coupon_code}",
       "quantity": "{$inputs.quantity}",
       "status": "placed",
       "complete": false
     }
   }

JSON Object Example

 contentType: application/json
 payload: 
   petOrder:
     petId: $inputs.pet_id
     couponCode: $inputs.coupon_code
     quantity: $inputs.quantity
     status: placed
     complete: false

Complete Runtime Expression

 contentType: application/json
 payload: $inputs.petOrderRequest

XML Templated Example

 contentType: application/xml
 payload: |
   <petOrder>
     <petId>{$inputs.pet_id}</petId>
     <couponCode>{$inputs.coupon_code}</couponCode>
     <quantity>{$inputs.quantity}</quantity>
     <status>placed</status>
     <complete>false</complete>
   </petOrder>

Form Data Example

 contentType: application/x-www-form-urlencoded
 payload: 
   client_id: $inputs.clientId
   grant_type: $inputs.grantType
   redirect_uri: $inputs.redirectUri
   client_secret: $inputs.clientSecret
   code: $steps.browser-authorize.outputs.code
   scope: $inputs.scope

Form Data String Example

 contentType: application/x-www-form-urlencoded
 payload: "client_id={$inputs.clientId}&grant_type={$inputs.grantType}&redirect_uri={$inputs.redirectUri}&client_secret={$inputs.clientSecret}&code{$steps.browser-authorize.outputs.code}&scope=$inputs.scope}"

Payload Replacement Object

Describes a location within a payload (e.g., a request body) and a value to set within the location.

Fixed Fields
Field Name Type Description
target string REQUIRED. A JSON Pointer or XPath Expression which MUST be resolved against the request body. Used to identify the location to inject the value.
value Any | {expression} REQUIRED. The value set within the target location. The value can be a constant or a Runtime Expression to be evaluated and passed to the referenced operation or workflow.

This object MAY be extended with Specification Extensions.

Payload Replacement Object Example

Runtime Expression Example

    target: /petId
    value: $inputs.pet_id

Literal Example

    target: /quantity
    value: 10

Runtime Expressions

A runtime expression allows values to be defined based on information that will be available within an HTTP message, an event message, and within objects serialized from the Workflows document such as workflows or steps.

The runtime expression is defined by the following ABNF syntax:

      expression = ( "$url" / "$method" / "$statusCode" / "$request." source / "$response." source / "$message." source / "$inputs." name / "$outputs." name / "$steps." name / "$workflows." name / "$sourceDescriptions." name / "$components." name / "$components.parameters." parameter-name)
      parameter-name = name ; Reuses 'name' rule for parameter names
      source = ( header-reference / query-reference / path-reference / body-reference )
      header-reference = "header." token
      query-reference = "query." name
      path-reference = "path." name
      body-reference = "body" ["#" json-pointer ]
      json-pointer    = *( "/" reference-token )
      reference-token = *( unescaped / escaped )
      unescaped       = %x00-2E / %x30-7D / %x7F-10FFFF
         ; %x2F ('/') and %x7E ('~') are excluded from 'unescaped'
      escaped         = "~" ( "0" / "1" )
        ; representing '~' and '/', respectively
      name = *( CHAR )
      token = 1*tchar
      tchar = "!" / "#" / "$" / "%" / "&" / "'" / "*" / "+" / "-" / "." /
        "^" / "_" / "`" / "|" / "~" / DIGIT / ALPHA
Examples
Source Location example expression notes
HTTP Method $method The allowable values for the $method will be those for the HTTP operation.
Requested media type $request.header.accept
Request parameter $request.path.id Request parameters MUST be declared in the parameters section of the parent operation or they cannot be evaluated. This includes request headers.
Request body property $request.body#/user/uuid In operations which accept payloads, references may be made to portions of the requestBody or the entire body.
Request URL $url
Response value $response.body#/status In operations which return payloads, references may be made to portions of the response body or the entire body.
Response header $response.header.Server Single header values only are available
workflow input $inputs.username or $workflows.foo.inputs.username Single input values only are available
Step output value $steps.someStep.pets In situations where the output named property return payloads, references may be made to portions of the response body or the entire body.
Workflow output value $outputs.bar or $workflows.foo.outputs.bar Single input values only are available
Components parameter $components.parameters.foo Accesses a foo parameter defined within the Components Object.

Runtime expressions preserve the type of the referenced value. Expressions can be embedded into string values by surrounding the expression with {} curly braces.

Specification Extensions

While the Workflows Specification tries to accommodate most use cases, additional data can be added to extend the specification at certain points.

The extension properties are implemented as patterned fields that are always prefixed by "x-".

Field Pattern Type Description
^x- Any Allows extensions to the Workflows Specification. The field name MUST begin with x-, for example, x-internal-id. Field names beginning x-oai- and x-oas- are reserved for uses defined by the OpenAPI Initiative. The value MAY be null, a primitive, an array or an object.

The extensions may or may not be supported by the available tooling, but those may be extended as well to add requested support (if tools are internal or open-sourced).

Security Considerations

The Workflows Specification does not enforce a security mechanism. Security is left to the implementer, though TLS, specifically HTTPS may be recommended for exchanging sensitive workflows.

Workflows can be JSON or YAML values. As such, all security considerations defined in RFC 8259 and within YAML version 1.2 apply.

Workflows are frequently written by untrusted third parties, to be deployed on public Internet servers. Processing a workflow description can cause both safe and unsafe operations to be performed on arbitrary network resources. It is the responsibility of the description consumer to ensure that the operations performed are not harmful.

IANA Considerations

The proposed MIME media types for Workflows are described below.

application/vnd.oai.workflows

The default (or general) MIME type for Workflows is defined as follows:

  Media type name: application

  Media subtype name: vnd.oai.workflows

  Required parameters: N/A

  Optional parameters: version (e.g. version=1.0.0 to indicate that the type of workflow conforms to version 1.0.0 of the Workflows Specification).

  Encoding considerations: Encoding considerations are identical to those specified for the application/json and application/yaml media types, respectively.

  Security considerations: See security considerations above.

  Interoperability considerations: N/A

Note: When using the application/vnd.oai.workflows media type the consumer should be prepared to receive YAML formatted content

application/vnd.oai.workflows+json

The proposed MIME media type for Workflows that require a JSON-specific media type is defined as follows:

  Media type name: application

  Media subtype name: vnd.oai.workflows+json

  Required parameters: N/A

  Optional parameters: version (e.g. version=1.0.0 to indicate that the type of workflow conforms to version 1.0.0 of the Workflows Specification).

  Encoding considerations: Encoding considerations are identical to those specified for the application/json media type.

  Security considerations: See security considerations above.

  Interoperability considerations: N/A

application/vnd.oai.workflows+yaml

The proposed MIME media type for Workflows that require a YAML-specific media type is defined as follows:

  Media type name: application

  Media subtype name: vnd.oai.workflows+yaml

  Required parameters: N/A

  Optional parameters: version (e.g. version=1.0.0 to indicate that the type of workflow conforms to version 1.0.0 of the Workflows Specification).

  Encoding considerations: Encoding considerations are identical to those specified for the application/yaml media type.

  Security considerations: See security considerations above.

  Interoperability considerations: N/A

Appendix A: Revision History

Version Date Notes
1.0.0 TBD Not yet released

Appendix B: Contextual scope / access for inputs and outputs

This quick image is to add some context / scope access overview for inputs, step parameters, step outputs and workflow outputs

Contextual Access Scope