Re: [xml-dev] XPath 2.0 Best Practice Issue: Graceful Degradation

[David Carlisle <davidc@nag.co.uk>]

> the XPath to perform a schema-validation check and the XPath check
> should be done elsewhere.  (This is pretty vague.

well in thi scase, I was arguing that its better not to do them at all,
as the more complicated tests limit the ability of the xpath to run on
multiple processors (you get no output at all unless you are using a
schema aware processor) and the simple expression (which even works on
xpath 1 processors) essentially autoimaticaly includes tests that teh
element is there and has a value castable as double, as teh result will
be naN if this is not the case, and it's easy to test for naN being teh
result of the expression.

> When designing an XPath statement, do not combine data processing,
> XPath checks, and schema-validation checks.  Instead, keep the three
> activities separate.
> 
> Do you agree with this?

yes, (in general) and also only code the extra checks if they are going
to check something that isn't already checked by the basic code.

David

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