Don't want name on DataRequirement.  Instead, we want to make PlanDefinition.action.input and PlanDefinition.action.output into complex structures.  Each should have the following: title 0..1 string : A human-readable label for the data requirement - used to label data flows in BPMN or similar diagrams.  Also provides a human readable label when rendering the data requirement that conveys its purpose to human readers requirement 0..1 DataRequirement : Defines the data to be provided as input/output relatedRequirementId 0.. id*: Points to an existing data requirement (PlanDefinition.action. [input/output] .requirement.id) that is shared by this input or output. Usage notes: relatedRequirementId allows indicating that an input to a parent activity is an input to specific child activities.  It also allows the output of one sub-activity to be identified as the input to a different activity Add an invariant requiring that input and output have either requirement or relatedRequirementId (must have one or at least one of the other, can't have both).