RE: [xsl] Namespace-aliasing and excluded namespaces

Subject: RE: [xsl] Namespace-aliasing and excluded namespaces
From: "Michael Kay" <mike@xxxxxxxxxxxx>
Date: Wed, 10 May 2006 19:46:08 +0100
namespace-alias in 1.0 is underspecified. In particular, there is no text in
the spec that describes its interaction with excluded namespaces -
specifically, it doesn't tell you whether to test a namespace URI against
the list of excluded namespaces before or after aliasing it. You just have
to make up the rules as you go along. Libxslt seems to be testing it neither
before nor after aliasing - since the rules for namespace aliasing override
some of the things said in the section on excluded namespaces, I don't think
one can argue that that's not one possible reading of the spec. In any case,
an XSLT 1.0 serializer is allowed to add any namespaces it likes at
serialization time.

We were well aware when we defined the more precise 2.0 rules for namespace
aliasing that there were many edge cases that weren't well covered by the
1.0 spec, and that we couldn't therefore guarantee backwards compatibility
with existing implementations.

I wouldn't particularly trust Saxon 8.1.1 on this - it's a rather old
release and the spec has been refined in many corner cases - but 8.7.1 is
doing the same, outputting all three namespace bindings.

Michael Kay

> -----Original Message-----
> From: Buchcik, Kasimier [mailto:k.buchcik@xxxxxxxxxxxx] 
> Sent: 10 May 2006 18:49
> To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx
> Subject: [xsl] Namespace-aliasing and excluded namespaces
> Hi,
> Can someone confirm that the stylesheet below should generate 
> the following?
> 1) With XSLT 1.0 processors (with MSXML.NET, Xalan-J, Saxon 6.5.3):
>   <foo/>
> 2) With XSLT 2.0 processors (run with Saxon 8.1.1):
>   <foo xmlns:ext="urn:test:ext" xmlns:ext-literal="urn:test:ext"
> xmlns:ext-target="urn:test:ext"/>
> For 2) the relevant pieces of spec seem to be:
> "A namespace node whose string value is a target namespace 
> URI is copied to the result tree, whether or not the URI 
> identifies an excluded namespace."
> "In the event that the same URI is used as a literal 
> namespace URI and a target namespace URI, the second of these 
> rules takes precedence."
> Libxslt seems to be confused by the aliasing of the same 
> namespaces, and
> reports:
> <foo xmlns:ext="urn:test:ext" xmlns:ext-literal="urn:test:ext"/>
> Scenario:
> <?xml version='1.0'?>
> <xsl:stylesheet version="1.0"
>   xmlns:xsl="";    
>   xmlns:ext-literal="urn:test:ext"
>   xmlns:ext-target="urn:test:ext"
>   extension-element-prefixes="ext-target">
>   <xsl:namespace-alias stylesheet-prefix="ext-literal"
> result-prefix="ext-target"/>
>   <xsl:template match="/">    
>     <foo xmlns:ext="urn:test:ext"/>	
>   </xsl:template>
> </xsl:stylesheet>
> Regards,
> Kasimier

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