When discussing Conformance (Section 14), line 780 says Portions of CTS conform to and use updated and simplified versions of the specifications. I guess it's possible for a spec's conformance rules to allow the CTS spec to both conform to it and to extend it, but it does sound somewhat paradoxical. Besides, the WS-Calendar spec says [lines 1553-1554] that "Specifications that...claim conformance with WS-Calendar SHALL define the business meaning of zero duration Intervals and I don't find that in the CTS spec.