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
