[xquery-talk] querying an xml file with namespaces

[Wolfgang Hoschek]

On Jan 11, 2006, at 2:17 PM, Michaël Michaud wrote:

> Hello,
>
> I try to query an xml file with nux XQueryUtil.
> First time, i get messages such as
>  "Prefix md has not been declared"
>
> I could get the result by adding something like
>  "declare namespace md="http://www.isotc211.org/2005/gmd";"
> in front of my query string.

That's the standard and hence recommended way of doing it.

>
> Now I try to read the namespaces first with another query
>  XQueryUtil.xquery(node, "//namespace::*")
> to automatically add the namespaces in front of my main query,
> but I get the message :
>  "The namespace axis is not available in XQuery"

This simply won't work. The namespace axis has been deprecated by the  
W3C, so Saxon followed suit and disabled it a few releases ago by  
toggling an internal flag. Namespaces continue to be available  
supported, of course. It's just the namespace axis iteration that's  
gone.

>
> Question : what is the simple method to query an xml file using
> namespaces ?

Depends on what you're trying to do.

You could write yourself a Java method or XQuery function that  
computes the namespaces in scope for a given element, then precede  
the query with the relevant declarations. For example, using standard  
XQuery functions such as fn:namespace-uri(Node) or similar.

The best solution might be to argue on the XOM mailing list for a  
public method returning the namespace declarations of a XOM  
XPathContext, such as nu.xom.XPathContext.toMap(). If this would be  
public I'd consider adding a query method that takes an XPathContext  
as additional input parameter, similar to the XOM XPath functionality.

Wolfgang.