Optimization/error reporting: cardinality checks & fu

Hi all,

I'm a bit confused about errors & optimizations in XPath/XQuery 
implementations, perhaps someone could help me clear it.

2.3.4 Errors and Optimization in XML Path Language (XPath) 2.0 says that 
implementations are free to perform arbitrary optimizations(such as skipping 
evaluation of somekind) as long as 1) The result is identical to when not 
being optimized, except for that errors are possibly not reported; and 2) 
that cardinality errors are still reported.

Section 2.3.4 uses the term "expression", and I presume functions are 
applicable to that discussion(functions are expressions).

Further, in 3.1.5 Function Calls, one can read this:

<quote>
Argument expressions are evaluated, producing argument values. The order of 
argument evaluation is implementation-dependent and a function need not 
evaluate an argument if the function can evaluate its body without evaluating 
that argument.
</quote>

I think the understanding is meant to be that an implementation is free to 
skip "evaluation" of an argument, and that the cardinality check is also free 
to be skipped if the argument as a whole has been skipped.

Am I right in my interpretation?


Cheers,

		Frans