[Bug 11713] [XPath 3.0] Rules for union types


--- Comment #8 from Michael Kay <mike@saxonica.com> 2011-05-03 08:27:26 UTC ---
>If I understand correctly, this new category of type includes all simple types
except list types. True?

False. It also excludes union types that are derived by restriction from other
union types.

And it also excludes unions whose member types are lists.

Perhaps we need a definition like this: a /generalized atomic type/ is either
an atomic type, or a union type whose member types are all /generalized atomic
types/. The instances of a generalized atomic type are atomic values. The
atomic member types of a generalized atomic type are (a) if it is an atomic
type, then that type, (b) if it is a union, then the atomic types in its
transitive membership. If A and B are generalized atomic types, then
derives-from(A, B) is true if for every type T among the member types of A
there exists a type U among the member types of B such that derives-from(T, U).

(My /generalized atomic type/ here is the same as /plain type/ in the previous
proposal. I'm just experimenting with different terms to see what reads best).

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Received on Tuesday, 3 May 2011 08:27:29 UTC