[Bug 29227] New: [XP31] Partially-defined focus


            Bug ID: 29227
           Summary: [XP31] Partially-defined focus
           Product: XPath / XQuery / XSLT
           Version: Last Call drafts
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: XPath 3.1
          Assignee: jonathan.robie@gmail.com
          Reporter: mike@saxonica.com
        QA Contact: public-qt-comments@w3.org
  Target Milestone: ---

XPath section 2.1.2 states:

If any component in the focus is defined, all components of the focus are

For streaming in XSLT 3.0 we are defining situations where this is no longer
the case: for example during streamed merging, it's possible to have the
context item and context position known, but the context size cannot be
determined without lookahead, so any call on last() throws a dynamic error.

I would therefore suggest:

(a) the above sentence should be deleted, to be replaced perhaps with a note:

Note: Normally, if any component in the focus is defined, all components of the
focus are defined. However, there may be situations where this is not the case,
for example with streamed processing.

(b) in the error conditions for position() and last() the sentence "A dynamic
error is raised [err:XPDY0002] if the context item is absent." should change to
say "context position"/"context size" rather than "context item".

I don't actually envisage any situations where the context item is present and
the context position is absent, nor situations where context position/size is
present and context item is absent, but I see no reason to rule such things out
for all possible invocations of XPath.

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Received on Thursday, 22 October 2015 11:57:27 UTC