[Bug 4855] [XPath] Undocumented incompatibility

http://www.w3.org/Bugs/Public/show_bug.cgi?id=4855

           Summary: [XPath] Undocumented incompatibility
           Product: XPath / XQuery / XSLT
           Version: Recommendation
          Platform: PC
        OS/Version: Windows XP
            Status: NEW
          Severity: normal
          Priority: P2
         Component: XPath
        AssignedTo: chamberl@almaden.ibm.com
        ReportedBy: mike@saxonica.com
         QAContact: public-qt-comments@w3.org


The following incompatibility should be documented in Appendix I.1

In XPath 1.0, the expression -x|y parsed as -(x|y), and returned the negation
of the numeric value of the first node in the union of x and y. In XPath 2.0,
this expression parses as (-x)|y. For example, given the untyped input element
<foo y="3"/> as the context node, the expression -@x|@y in XPath 1.0 returns
-3, but in XPath 2.0 (without static type checking) returns 3.