WDL Documents

A WDL document is a file that contains valid WDL definitions.

A WDL document must contain:

• A version statement on the first non-comment line of the file.
• At least one struct definition, task definition, workflow definition.

A WDL document may contain any combination of the following:

• Any number of import statements.
• Any number of struct definitions.
• Any number of task definitions.
• A maximum of one workflow definition.

To execute a WDL workflow, the user must provide the execution engine with the location of a "primary" WDL file (which may import additional files as needed) and any input values needed to satisfy all required task and workflow input parameters, using a standard input JSON file or some other execution engine-specific mechanism.

If a workflow appears in the primary WDL file, it is called the "top-level" workflow, and any workflows it calls via imports are "subworkflows". Typically, it is an error for the primary WDL file to not contain a workflow; however, an execution engine may choose to support executing individual tasks.