[Phoenix] Constraints on XML documents to work with Yulup (elaborated)

[Andreas Wuest]

Hi

Let me give some examples for the constraints mentioned below.

On 22.9.2006 21:46 Uhr, Andreas Wuest wrote:

> Hi
> 
> Summing up the previously mentioned problems, an XML source document
> and its associated XSLT have to fulfil the following constraints to 
> currently work with Yulup:
> 
> XML source: (1) IFF namespace(s) are used in a XML document, then all
> elements MUST be prefixed.

This means that a document

<foo xmlns="foo.org">
   <bar/>
</foo>

is ruled out, and instead must look like

<f:foo xmlns:f="foo.org">
   <f:bar>
</f:foo>

> (2) IFF namespace(s) are used in a XML document, then all namespace 
> declarations MUST occur at the document root element.

This means that a document

<f:foo xmlns:f="foo.org">
   <b:bar xmlns:b="bar.org"/>
</f:foo>

is ruled out, and instead must look like

<f:foo xmlns:f="foo.org" xmlns:b="bar.org">
   <b:bar>
</f:foo>

> (3) IFF namespace(s) are used in a XML document, then namespace 
> prefixes MUST NOT be overridden in a descendant element (but this is
>  ruled out by constraint number 2 anyway).

This means that a document

<f:foo xmlns:f="foo.org">
   <f:bar xmlns:f="bar.org"/>
</f:foo>

is ruled out, and instead must look like

<f:foo xmlns:f="foo.org" xmlns:b="bar.org">
   <b:bar>
</f:foo>

The same goes for documents which override the default namespace like

<foo xmlns="foo.org">
   <bar xmlns="bar.org"/>
<foo>


> XSLT: (4) Namespace prefix tuples (i.e. {prefix,namespace}) used in
> the XSLT stylesheet MUST be equal to those used in the XML source.
> 
> Note that you can happily use XML documents which don't make use of 
> namespaces though.
> 
> Note also that we might be able to drop constraint number (1) by 
> introducing custom prefixes for all elements.
> 
> Note also that we might be able to drop constraint number (2) by
> first gathering all namespace information contained in that document,
> but this would be mutually exclusive with solving constraint number
> (3).
> 
> Note also that we might be able to drop constraint number (4) by
> copying all namespace declarations used in the XSLT stylesheet to an
>  intermediate copy of the XML source.
> 
> And last but not least, note that implementing namespace-unawareness
>  resolves all of those 4 constraints (although at the cost of
> introducing new problems).

New problems like the one mentioned earlier by Thomas Comiotto:

> The only problem one can run into with this approach is in situations
> where the xpath expression becomes ambiguous when ignoring ns
> information, i.e. a document that has
> 
> foo:table/foo:tr/xhtml:td/text()
> 
> xhtml:table/xhtml:tr/foo:td/text()
> 
> Never came across this, but it can't be ruled out either of course;)

-- 
Kind regards,
Andi