Special cases for PrefixRewrite in C14N 2.0

For these following three XML documents 1, 2, and 3 here is what I think they should canonicalize to with prefixRewrite according to the current spec - 1a, 2a and 3a. But I have also put an alternative  for each - 1b, 2b and 3b.    

 

Example 1:  with namespace redefinition

 

<a:foo xmlns:a="http://a1">

  <a:bar xmlns:a="http://a2"/>

</a:foo>

 

In the above example at first  prefix "a" is defined to  namespace http://a1  and then redefined to http://a2

 

With prefix rewriting should prefix "a" be rewritten to two different namespaces ns0 and ns1? Or should it be one namespace ns0 with redefinition.   I.e. should it be 

 

1a)

<ns0:foo xmlns:ns0="http://a1" >

  <ns1:bar xmlns:ns1="http://a2"/>

</ns0:foo>

 

Or should it be 

 

1b)

<ns0:foo xmlns:ns0="http://a1" >

  <ns0:bar xmlns:ns0="http://a2"/>

</ns0:foo>

 

I think the spec says it should be 1a)

 

 

 

Example 2: with two prefixes defining the same namespace

<a:foo xmlns:a="http://a1">

  <b:bar xmlns:b="http://a1"/>

</a:foo>

 

In this example both "a" and "b" are defined to the same namespace  http://a1

 

So should they be rewritten to two different prefixes or to the same prefix?

 

I.e. should it be canonicalized to

2a)

<ns0:foo xmlns:ns0="http://a1">

  <ns1:bar xmlns:ns1="http://a1"/>

</ns0:foo>

 

Or should it be 

2b)

<ns0:foo xmlns:ns0="http://a1">

  <ns0:bar/>

</ns0:foo>

 

Again I think the spec says it should be 2a).       But maybe 2b) makes more sense, i.e. should we say that each URI should be mapped to one prefix?

 

 

Example 3: With prefixes being pushed down

<a:foo xmlns:a="http://a1" xmlns:b="http://a2" >

  <b:bar>

  <b:bar>

</a:foo>

 

Should each b get mapped to different prefixes?  I.e. Should it be

 

3a)

<ns0:foo xmlns:ns0="http://a1" >

  <ns1:bar xmlns:ns1="http://a2" >

  <ns2:bar xmlns:ns2="http://a2" >

</ns0:foo>

 

Or should it be

3b)

<ns0:foo xmlns:ns0="http://a1" >

  <ns1:bar xmlns:ns1="http://a2" >

  <ns1:bar xmlns:ns1="http://a2" >

</ns0:foo>

 

 

Again according to the spec , it should be 3a)

 

I am thinking that we should change the definition of prefixRewrite so that we go by URI and not by prefix.  i.e.  each visibility utilized prefix gets mapped to a new prefix, so that there is a 1:1 mapping between URIs and new prefixes, but not a 1:1 mapping between original prefixes and new prefixes.  With this definition  we would get 1a), 2b and 3b) which I think makes more sense.

 

 

Pratik