BPMN21 — optional source and target refs for data association

dataOutputAssociation/@sourceRef should be optional, not required.
dataInputAssociation/@targetRef should be optional, not required.
This is to support non-executable models (<a href="http://www.osoa.org/jira/browse/BPMN-381" title="Abstract BPMN Profile"><strike>BPMN-381</strike></a>), since these elements are part of the data interface of the parent node, which is unspecified in non-executable models. The other end of the association, the dataObject, is still required.

Comments:
From: ssamoojh@ca.ibm.com created: Thu, 14 May 2009 11:04:19 -0500 (CDT)
Counterproposal - Rather than making the source or target optional, instead 'lighten' the spec text. The spec currently states that the source or target must be an ItemAwareElement. In the case of non-executable models, the source or target may be the FlowElement itself. So my proposal is to tweak the spec text, so as to allow this.