[Bug 30169] New: [XP31] Definition of pure union type allows unions with unions that have lists

https://www.w3.org/Bugs/Public/show_bug.cgi?id=30169

            Bug ID: 30169
           Summary: [XP31] Definition of pure union type allows unions
                    with unions that have lists
           Product: XPath / XQuery / XSLT
           Version: Recommendation
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: minor
          Priority: P2
         Component: XPath 3.1
          Assignee: jonathan.robie@gmail.com
          Reporter: abel.braaksma@xs4all.nl
        QA Contact: public-qt-comments@w3.org
  Target Milestone: ---

The definition in section 2.5 reads:

   [Definition: A pure union type is an XML Schema union type that satisfies 
   the following constraints: (1) {variety} is union, (2) the {facets} property
   is empty, (3) no type in the transitive membership of the union type has 
   {variety} list, and (4) no type in the transitive membership of the union 
   type is a type with {variety} union having a non-empty {facets} property].

Item (4) appears to allow unions with members that are unions and repeats item
(2) in its clause, but by doing so, it does not disallow variety list (item (3)
is not repeated).

Perhaps we can make the definition recursive (not sure this makes this
simpler)? 

(4) each type in the transitive membership of the union is a generalized atomic
type.

Though I admit I may be reading / understanding this wrong. Does "transitive
membership" here mean it includes any nested union members? If so, this does
not seem to be the mathematical definition of "transitive", but I'm not a
mathematician and I wonder whether the definition should need to rely on such
knowledge.

Hardly a severe bug, the text around the definition makes clear what the intent
is.

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Received on Saturday, 19 August 2017 15:54:36 UTC