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Namespace prefixes when using path() extensio

Added by Anonymous over 13 years ago

Legacy ID: #8924532 Legacy Poster: Antony Scerri (antonyscerri)

Hi I had a quick question regarding the use of the path extension function. I'm currently using this with the last release of SaxonB, so it may be something which has been changed/fixed later on although I suspect not. When calling this extension with an element defined in a namespace through the use of a default namespace declaration (so no explicit prefix) this function returns an xpath without any prefix on the element names even when there is a matching one declared in the current context (I'm doing this within XQuery). From the source it looks like this is intentional, there is a comment to the effect that the original prefix will be preserved and so I assume when there isnt one it will not include one. I'm intending on using this to store information in an XPointer type way for later use to resolve back to the element, one such use case may be passing this back to the evaluate extension. However this isnt going to work without the namespace prefixes being added to the path for it to work in the context of the current document on the assumption they will be declared equivalent at the point of evaluation. So I'm curious as to whether this is a bug, or something for which this function wasnt intended, or have I missed an option/configuration somewhere. Thanks Tony


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RE: Namespace prefixes when using path() extensio - Added by Anonymous over 13 years ago

Legacy ID: #8924738 Legacy Poster: Michael Kay (mhkay)

The main reason there isn't a similar path() function in the standard library is the difficulty in finding a good answer to this question. The current saxon:path() function is useful for diagnostic use, but it doesn't create a path expression that can be put back into saxon:evaluate() to get back the original node. This use case inspired a new addition to XPath 3.0, the ability to use "EQNames" in the form "uri":local wherever a QName can be used. Your mail reminds me that we need a standard function to generate paths in that form - I've put this in a requirements bug entry so it will appear on the WG agenda. Michael Kay Saxonica

RE: Namespace prefixes when using path() extensio - Added by Anonymous over 13 years ago

Legacy ID: #8924883 Legacy Poster: David Lee (daldei)

Amazing. Just this morning I hit he problem of having to represent a path in a way I could both use it as a XSLT match path OR deconstruction it into the list of parent/child component qnames. Until this morning I was ignoring namespaces and was just doing name/name/name/name ... works great without namespaces, but now I need to put in the namespaces. I guess I'm too early for XPath 3 ... but please put in my vote for a standard way to do this ! Maybe I'll use Clark notation for now and decode it later (?) or maybe use prefixes but then I have to declare the namespaces appropriately. Thanks.

RE: Namespace prefixes when using path() extensio - Added by Anonymous over 13 years ago

Legacy ID: #8926632 Legacy Poster: Antony Scerri (antonyscerri)

Thanks for the response. Namespaces and handling of prefixes have always caused some issues. I would think a simple extension that recognised any namespace declarations and their associated prefixes (in either the XSLT or XQuery contexts) could then put those prefixes on the XPaths, it would then match up when executing a call to evaluate. I checked the documentation and the saxon:path() documents does have the following which may need ammending slightly: "The resulting string can be used as input to the evaluate() function, provided that any namespace prefixes it uses are declared." This doesnt quite cover the case where the document doesnt use prefixes, and doesnt set any default namespace in the query context, not that it would still cover the case where multiple default namespaces were used in a document down the path to a given node. I'll have a go at another extension which produces paths using existing namesapce declaration in the XQuery to apply prefixes as that should meet my needs for the time being. Tony

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