XSLT (XPath) cannot find where the namespace declaration is

Yesterday I got stack a tricky features of XML.

Well, somehow I had to remove redundant the default namespace declarations (something looking like attribute "xmlns") from a large number of huge size of XML documents.  That job is incomplete, and this is intermediate memorandum.

Before really doing the job, I wanted to see how many instances are found where.  It was surprising that XSLT cannot do the job.  The "namespace::" syntax of XPath does not find the literal text in XML seriarization, but rather matches conceptual namespace nodes which are copied to all child elements [XPath].  So it cannot detect redundant NS declaration.

I think it is necessary to program with XML parser.  I wrote a ruby script to work with libxml2 Reader interface.