Workflow

A workflow represents a set of actions and transitions that form an executable flow diagram

Construction

A workflow variable is a structure that encapsulates the actions and routing needed to run a workflow.

Workflow structure syntax

The basic structure of a workflow is shown below:

workflowname = workflow in "category"
    // Description
    (in name as type (description)? (optional)?)*
    (out name as type (description)?)*
    exit ("transition")*

    START
    (PHASE|EVENT)*
end    

• workflowname is the variable name that will be the id of the workflow
• category is the group to categorise the workflow with similar workflows
• description is a user description to understand what the workflow does
• the in syntax represent the input arguments for this workflow
• the out syntax represents the output data for this workflow
• the exit syntax represents the list of transition names from this workflow
• START is the Start event syntax
• PHASE is the Phase syntax
• EVENT is the Event syntax

Start event syntax

The start event represents the initial point of the workflow which then routes using a transition to the first activity to run.

The START event is defined as:

WF_START
    TRANSITION
end

• TRANSITION is the Transition syntax which routes to the first activity to run.

Phase syntax

A phase represents a section of the workflow that is independently tracked and contains all the workflow activities.

The PHASE structure is defined as:

phase "name" (retries int)? (delay int timeunit)? (then reschedule in timeunit)? (external)?
    (statement|WORKFLOW_BODY)*
end

• retries is the number of attempts to retry this phase if it fails, default is 0
• delay is the amount of time to delay before retrying, default is 30 seconds
• reschedule will happen if the retries have been exhausted and will re-run the entire workflow
• external indicates that this phase runs external to the workflow and will be reported independently
• statement is any OpenDataDSL statement
• WORKFLOW_BODY is the Workflow body syntax

Event syntax

Events are generally used to mark the termination of a workflow to indicate success or failure.

The EVENT structure is defined as:

WF_EVENT name as "success|failed"
    (assign|return|TRANSITION)*
end

• name is the activity name which can be routed to using a transition
• assign is an assignment statement, e.g. output.message = "ok"
• return is a return statement, e.g. return "ok"
• TRANSITION is the Transition syntax indicating where to route to next

Workflow body syntax

This is the main list of activities performed by the workflow.

The WORKFLOW_BODY syntax is defined as:

(EVENT|ACTION|GATEWAY|WORKFLOW)

• EVENT is an Event syntax
• ACTION is an Action syntax
• GATEWAY is a Gateway syntax
• WORKFLOW is a Workflow syntax

Transition syntax

A transition represents a connector between activities which defines the routing within the workflow.

The TRANSITION syntax is defined as:

"name" -> activity_name

• name is the name of the transition as defined by the activity you are connecting from
• activity_name is the name of the activity you want to route to

Action syntax

An action is a configuration of a workflow action within the workflow.

The ACTION syntax is defined as:

WF_ACTION activity_name input
    (assign|TRANSITION)*
end

• activity_name is the unique name (within the workflow) that you give to this activity, this will be used to route the flow to
• input is the name of the variable to assign input data to, this will be used in the configuration of the action
• assign is an assignment statement, usually used for assigning input data to the input arguments on the action
• TRANSITION is the Transition syntax used to map the exit transitions of the action to activities in this workflow

Gateway syntax

A gateway is a special type of Action used as a decision node within a workflow.

The GATEWAY syntax is defined as:

WF_GATEWAY activity_name input
    (assign|TRANSITION)*
end

• activity_name is the unique name (within the workflow) that you give to this activity, this will be used to route the flow to
• input is the name of the variable to assign input data to, this will be used in the configuration of the gateway
• assign is an assignment statement, usually used for assigning input data to the input arguments on the gateway
• TRANSITION is the Transition syntax used to map the exit transitions of the gateway to activities in this workflow

Workflow syntax

The workflow syntax within a workflow is used to configure another workflow as a sub-workflow.

The WORKFLOW syntax is defined as:

WF_WORKFLOW activity_name input
    (assign|TRANSITION)*
end

• activity_name is the unique name (within the workflow) that you give to this activity, this will be used to route the flow to
• input is the name of the variable to assign input data to, this will be used in the configuration of the sub-workflow
• assign is an assignment statement, usually used for assigning input data to the input arguments on the sub-workflow
• TRANSITION is the Transition syntax used to map the exit transitions of the sub-workflow to activities in this workflow

Properties

A workflow variable has the following properties:

Name	Description	Type
category	A category is used to group similar workflows together	Scalar(String)
description	A description of what this workflow does	Scalar(String)
exits	The exit transitions from this workflow	List(String)
id	The ID of this action	Scalar(String)
inputs	The input variable args	List(Arg)
outputs	The output variable args	List(Arg)
script	The actual code used to create this workflow	Scalar(String)
version	The version of this workflow	Object

Methods

A workflow variable has the following methods:

Name	Description	Return Type
run(in, out)	Runs this workflow and returns the name of the exit transition	Scalar(String)

Example Usage

You can run a workflow in ODSL code by creating an input object and an output object. The input object should contain the in arguments required by the workflow and the output object should be empty.

When the workflow runs, it populates the output object with any output arguments defined.

oi = Object()
oi.user = "World"
oo = Object()
workflow.run(oi, oo)
print oo

Example output:

{
  "_id": "oo",
  "_type": "#Object",
  "_links": {},
  "workflow": {
    "_id": "output",
    "act_print": {
      "_id": "output",
      "message": "Hello World"
    }
  }
}

Further Reading

• Workflow service for saving and using workflows in the server.