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

Michael Kay wrote:
> Well, it's really all about contracts, isn't it? If you write a piece of
> code, you need to establish a contract with your caller. And the essence of
> that contract is whether you validate the data, or the caller validates. If
> the caller isn't contracted to validate the data against an agreed schema,
> then you're best off validating it yourself. And doing that within the logic
> of the XPath expression itself, as you've shown, is not a particularly nice
> approach.
I think it is more than contracts. 

It is also QC and QA, both internal and external. And test-driven 
development. And continuous improvement: in the ISO 9000* model, having 
a defect reporting system in place is essential. One of the many 
troubles with XSD-style schema systems is that they encourage a big bang 
mentality, where you have to try to make all sorts of decisions about 
structure and type that are unnecessary or which can be left to emerge, 
while making it difficult to add constraints based on feedback from 
processes about what the real problems might be.

Rick Jelliffe

* http://en.wikipedia.org/wiki/ISO_9000

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