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ORA-XQ-243-C: Need to clarify: optimization on XQuery expression should not raise new errors

From: Stephen Buxton <Stephen.Buxton@oracle.com>
Date: 16 Feb 04 14:12:47
Message-Id: <200402162212.i1GMCmG28380@rgmgw5.us.oracle.com>
To: public-qt-comments@w3.org
Cc:

SECTION 2.5.3: Errors and Optimization

In 2.5.2 and 2.5.3, it is clear from the spec that if an expression raises a dynamic error, than an implementation may choose to return a value or raise the dynamic error. 

However, the spec needs to clarify the rules when there 
are no errors in an exhaustive implementation.

In general, we should state the following regarding Errors and Optimizations:
An exhaustive mode XQuery evaluation evaluates every expression of an XQuery except for the case
of conditional and typeswitch expressions in which only the actually selected
branch can potentially raise dynamic errors.

A non-exhaustive mode XQuery evaluation is an optimized mode XQuery
evaluation which
may NOT evaluate every subexpression of an expression so as to achieve optimal
performance.

Rule1: Non-determinism  in the presense of error.
If the exhaustive mode XQuery evaluation raises dynamic errors, then an optimized
mode XQuery evalution is permitted to either  raise dynamic errors or
return a value. 

Rule2: Determinism in the absense of error.
If the exhaustive mode XQuery evaluation raises NO dynamic error,
then an optimized
mode XQuery evalution is NOT permitted to raise any dynamic errors and should
return the same value as the exhaustive mode XQuery expression. 

- Steve B.
Received on Monday, 16 February 2004 17:12:50 UTC

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