Re: Concerned about the increasing reliance on XPath
On 07/05/2011 14:51, Costello, Roger L. wrote: > Hi Folks, > > XPath is a fabulous language. It is incredibly powerful. It is a large, rich language. > > I have observed in increasing usage of XPath. > > For example, in XML Schema 1.1 the new assert element uses XPath to express constraints: > > <assert test="XPath" /> > > XPath gives a lot of power to the assert element. > > But it also means that a lot of power is needed to evaluate the assert element. > > To evaluate that tiny, innocuous assert element you need to implement the entire XPath language. > I'm much more concerned about the proliferation of different dialects and varieties of XPath. I strongly encouraged the XML Schema WG to support the whole of XPath 2.0 in assertions for two reasons: (a) it's very difficult for users if XSD, XForms, XProc, XSLT, etc all use different XPath subsets (b) it means that XSD implementors can use an off-the-shelf XPath engine rather than implementing their own. (Both existing XSD 1.1 processors - Xerces and Saxon - use XPath libraries that were originally written for a different purpose). Michael Kay Saxonica
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