DTV — Reference to 'conceptual schema'

The definition of 'calendar' in clause 10.1 relies upon SBVR's 'conceptual schema'. However:
1. 'conceptual schema' is not included in the list of adopted SBVR concepts in clause 4.
2. SBVR 1.1 moved 'conceptual schema' to clause 10.1.2.1, which means this concept is part of the semantic and logical foundation of SBVR, but not actually in any of the SBVR vocabularies.

Text from the SBVR definition of 'conceptual schema' is integrated into the existing definition of 'calendar' to combine them and eliminate the dependency upon the SBVR concept.