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[Bug 1382] [XQuery] some editorial comments on A.1.1 grammar-note: occurrence-indicators

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Date: Thu, 07 Jul 2005 03:22:24 +0000
To: public-qt-comments@w3.org
Message-Id: <E1DqMy0-0004Rl-Gc@wiggum.w3.org>


------- Additional Comments From cmsmcq@w3.org  2005-07-07 03:22 -------
Here is a proposed rewording to make clearer that the
priority rule applies in all cases, not just cases of

       As written, the grammar in A.1 is ambiguous for some forms
       using the '+' and '*' Kleene operators.  The ambiguity is
       resolved as follows:  these operators are tightly bound
       to the SequenceType expression, and have higher precedence
       than other uses of these symbols. Any occurrence of '+'
       and '*', as well as '?', following a sequence type is
       assumed to be an occurrence indicator.  That is, a 
       "+", "*", or "?" immediately following an ItemType MUST
       be an OccurrenceIndicator.  Thus, "4 treat as
       item() + - 5" MUST be interpreted as (4 treat as item()+) - 5,
       taking the '+' as an OccurrenceIndicator and the
       '-' as a subtraction operator. To force the interpretation
       of "+" as an addition operator (and the corresponding
       interpretation of the "-" as a unary minus), parentheses
       may be used:  the form "(4 treat as item()) + -5" surrounds
       the SequenceType expression with parentheses and leads
       to the desired interpretation.

       This rule has as a consequence that certain forms which
       would otherwise be legal and unambiguous are not
       recognized:  in "4 treat as item() + 5", the "+" is
       taken as an OccurrenceIndicator, and not as an operator,
       which means this is not a legal expression.
Received on Thursday, 7 July 2005 03:22:26 UTC

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