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From Structures, 3.15.6, Schema Component Constraint: Simple Type Restriction (Facets): 3 The facets of R [the restriction] [must] ·constitute a restriction· of the {facets} of B [the base] with respect to S [a set of new facets]. Within the definition of "constitute a restriction", the governing clause is: 2 Every facet in B is in R unless it is of the same kind as some facet in S. If we interpret "unless" to mean that the facet in B is prohibited if is is of the same kind as some facet in S, then reading back into the Constraint we find that the constraint precludes a facet of B from being also a facet of R if there is a facet of the same kind in S. This needs to be made clear; "unless" can also be interpreted as making no statement about whether a facet B is in R if it is of the same kind as some facet in S. Recommend "unless it is of the same kind as some facet in S" be changed to read "if and only if it is not of the same kind as some facet in S". Since this is what is needed to resolve Datatypes bug 2246, and 2246 blocks Structures bug 2781, this change might impact the resolution of 2781.
At today's call, the WG accepted a wording proposal which recasts clause 2 of the definition of 'constitutes a restriction'. The new text is: 2 Every facet in B is in R, unless it is of the same kind as some facet in S, in which case it is not included in R. This is not the wording proposed by the originator, but it does seem to accomplish the same clarification. So I'm marking this as resolved. Dave, as originator please confirm your acceptance of the disposition by changing the status to CLOSED. If we don't hear from you in two weeks, I'll close it myself.