Joining two relative URIs (public-ietf-w3c-draft)

Dear all,

the email below is a draft to be sent as 
"mailto:public-ietf-w3c@w3.org?cc=uri-ig@w3.org&subject=Joining two 
relative URIs 
<mailto:public-ietf-w3c@w3.org?cc=uri-ig@w3.org&subject=Joining%20two%20relative%20URIs>"  
next Monday on behalf of the xml core working group.

best regards
Konrad Lanz

#--- snip ---
Dear T. Berners-Lee, R. Fielding, L. Masinter,

According to an email by John Boyer 
<http://lists.w3.org/Archives/Public/public-xml-core-wg/2006Mar/0004.html> 
we need to apply the inheritance rule 
<http://www.w3.org/TR/xmlbase/#resolution> to xml:base when 
canonicalizing a XPath node-set over a XML document using C14n 
<http://www.w3.org/TR/xml-c14n>'s successor Canonical XML 1.1 
<http://www.w3.org/XML/Group/2006/02/WD-xml-c14n11>. This can be 
critical when nodes in a document become an orphan. For a simple example 
cf. to the post by Henry S. Thompson 
<http://lists.w3.org/Archives/Public/public-xml-core-wg/2006Mar/0036.html> 
where critical xml:base context could be lost by for instance applying 
an XPath-Filter <http://www.w3.org/TR/xmldsig-core/#sec-XPath>(2.0 
<http://www.w3.org/TR/xmldsig-filter2/>).

Consider the following

<a>
  <b xml:base="test1/somefile1.ext#abc?def">
    <c xml:base="test2/somefile2.ext"/>
  </b>
</a> 

with the 'b' being clipped out, we'd get

<a>
   
     <c xml:base="test1/test2/somefile2.ext"/>
  
</a> 

and the relevant information of xml:base gets pushed down to the child nodes.

If b's xml:base was an absolute URI one would absolutize using the 
algorithm in 5.2 in RFC 2396 <http://www.ietf.org/rfc/rfc2396.txt>. 
However the example above requires the joining of two relative URIs 
which we believe is not defined in RFC 2396 
<http://www.ietf.org/rfc/rfc2396.txt>. It may nevertheless be defined in 
RFC 3986 <http://www.ietf.org/rfc/rfc3986.txt> in section "5.2. Relative 
Resolution" by applying applying the algorithm in 5.2 ignoring the note 
"that only the scheme component is required to be present in a base URI".

Our question is: Is this covered in the scope of RFC 3986 
<http://www.ietf.org/rfc/rfc3986.txt> ?

The group currently discusses the resolution above as an alternative to 
adapting section 5.2 step 6 
<http://lists.w3.org/Archives/Public/public-xml-core-wg/2006Mar/0041.html> 
of RFC 2396 <http://www.ietf.org/rfc/rfc2396.txt> (currently referenced 
in xml base <http://www.w3.org/TR/xmlbase/#resolution> and C14n) 
<http://www.w3.org/TR/xml-c14n> or not to apply inheritance rules 
<http://www.w3.org/TR/xmlbase/#resolution> at all when nodes in a 
document become an orphan.

Your comments are greatly appreciated.
best regards on behalf of the xml-core-group

Konrad Lanz

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-- 
Konrad Lanz, IAIK/SIC - Graz University of Technology
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