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When different arms have different workflows, the workflow can be defined by referencing a single WorkflowDef element for each arm, or by referencing WorkflowDef elements in the containing study cells, represented as StudyEventGroup elements. each of them will reference a different WorkflowDef element under MetaDataVersion.
In case all arms have the same workflow (such as often in a blinded study), a single WorkflowDef element under MetaDataVersion can describe the workflow that is common to all arms. In such a case every arm will reference the same workflow.