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When reading section "17.1 Casting from primitive types to primitive types" found in the working draft of 4th April,[1] I think contradictory statements can be found. The first statement, which is the second paragraph in the section, reads: "[XML Schema Part 2: Datatypes Second Edition] defines xs:NOTATION as an abstract type. Thus, casting to xs:NOTATION is not permitted." However, when I interpret the "casting table" found a bit below, I judge that xs:NOTATION can be cast to itself(and maybe xs:string). What is correct becomes quickly complicated, in my opinion. I don't see how the situation of casting from xs:NOTATION to xs:NOTATION would occur in practice, since the data type is abstract. Hence, does the table document a casting which is in theory doable but cannot occur in practice? If the "casting table" also included sub-classes of the data types(e.g that casting to/from a xs:NOTATION derivation) it would to me make sense, but I don't see how it does that. Considering that one user(me) is at least confused, the formerly mentioned paragraph could perhaps be deepened a bit. Cheers, Frans 1.http://www.w3.org/TR/2005/WD-xpath-functions-20050404/#casting-from-primitive-to-primitive
Yes, we probably need to explain this better. Casting to subtypes of xs:NOTATION is allowed, but the standard mechanism of casting across to xs:NOTATION and then down to the subtype doesn't really work here. Michael Kay
The WGs decided on the joint call on July 12, 2005 to add wording to section 17.1 of the F&O to clarify that casting is not permitted from xs:NOTATION to xs:NOTATION, since it is an abstract type, although it is permitted from one subtype of xs:NOTATION to another. The entry in the table at the intersection of xs:NOTATION and xs:NOTATION should be changed to "M".