29619 2016-05-08 14:11:08 +0000 [FO31] Casting to abstract types 2016-05-24 16:07:18 +0000 1 1 1 Unclassified XPath / XQuery / XSLT Functions and Operators 3.1 Candidate Recommendation PC Windows NT CLOSED WORKSFORME P2 normal --- 1 abel.braaksma mike public-qt-comments oldest_to_newest 126373 0 abel.braaksma 2016-05-08 14:11:08 +0000 Common sense seems to dictate that casting to abstract types is not allowed. However, the only hint I could find is in places where the text mentions that casting to xs:NOTATION is not allowed *because* it is an abstract type. The closest I got was in 19.3.2, which says: "It is always possible to cast an atomic value A to a type T if the relation A instance of T is true, provided that T is not an abstract type." However, this indicates that casting is *not always possible*. It doesn't (necessarily) say that casting to a parent that is abstract is *always* a failure. Furthermore, sections 19.3.3 and 19.3.4 do not mention abstract types at all (and I'm unsure the text there covers TT of abstract type). Unless I am misunderstanding these sections, I propose to add a (tiny) section under 19.3, something like: 19.3.1 Casting to abstract types If TT is an abstract type, casting always fails. It doesn't matter in this case if TT is a parent type of ST, or if TT is equal to ST. 126554 1 mike 2016-05-24 15:21:52 +0000 We concluded that the paragraphs in 9.1 that exclude casting to xs:NOTATION, xs:anyAtomicType, or xs:anySimpleType are adequate. 126563 2 abel.braaksma 2016-05-24 16:07:12 +0000 For sake of reference: during the discussion it became apparent that simple types cannot be abstract (by XSD rules), only complex types can, and that the text in the spec means "abstract type" in a different vein than the W3C XML Schema says.