[Bug 14652] [XPath 3.0] Definition of 'subtype' is incorrect/inconsistent

http://www.w3.org/Bugs/Public/show_bug.cgi?id=14652

--- Comment #2 from Michael Kay <mike@saxonica.com> 2011-11-15 16:34:08 UTC ---
>[Definition: A sequence type A is a subtype of a sequence type B if subtype(A,
B) is true.] 

Seems OK to me. One could add the rider:

When subtype(A, B) is true, it is always the case that for any value V, (V
instance of A) implies (V instance of B).

Note: the converse is not necessarily true: for example every instance of
union(P, Q) is also an instance of union(P, Q, R), but there is no subtype
relationship between these two types.

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Received on Tuesday, 15 November 2011 16:34:39 UTC