Changing base URIs

I think the problem that Toman raises in message #83 is significant.
Although many of the particular cases can be worked out with XPath 2.0
and with XSLT, I wonder if we should consider a new atomic step,
p:set-base-uri:

<p:declare-step type="p:set-base-uri">
  <p:input port="source"/>
  <p:output port="result"/>
  <p:option name="base-uri"/>  
</p:declare-step>

Where we define base-uri, like replace in p:string-match, as an XPath
Expression.

The result of this step is a new document, identical to the source,
except that it has a new base URI.

The 'base-uri' expression is evaluated *by the step*. I think we have
a step that sets a variable binding automatically (though I can't find
that in the current draft???), so we could say that $p:current-base-uri
is set to the base URI of the source document. This gives XPath 1.0
implementations a mechansim for writing things like this:

  <p:set-base-uri base-uri="concat(substring-before($p:current-base-uri,'.xml'),'-processed.xml')"/>

                                        Be seeing you,
                                          norm

-- 
Norman Walsh <ndw@nwalsh.com> | It costs a great deal to be reasonable;
http://nwalsh.com/            | it costs youth.--Madame de la Fayette