Re: [xsl] xmlns in the root element prevents transformation

["Michael Kay mike@xxxxxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>]

Failing to appreciate the implications of a namespace declaratoin in the
source document is probably the most common source of XSLT questions on
StackOverflow - if you search there for "XSLT default namespace" you will find
at least 600 questions from people who have fallen into this trap. It's
particularly invidious beccause (a) the symptoms of the failure are usually
wrong results rather than any kind of error, and there's nothing in the wrong
results that hints at a namespace problem, and (b) many people try to pick up
XSLT from very elementary tutorials that only handle the simplest of
constructs, and leave out any discussion of namespaces as if they are somehow
an advanced feature that you don't need to worry about until later.

It's also invidious because although the problem was recognised very early on,
it's proved impossible to fix without creating backwards compability problems.
The xpath-default-namespace attribute in XSLT 2.0 helps, but only if you know
what the problem is and know that you need to use it. In Saxon I've been
experimenting with another solution, which is for bare unqualified names in
the stylesheet to match elements in any namespace or none - but for
conformance reasons, that option can't be the default, so beginners still fall
straight into the trap. I've also tried heuristics that attempt to detect when
users are falling into the trap (specifically, when a namespace is used in the
source document and isn't declared in the stylesheet) but I fear that users
who don't even know that these peculiar xmlns things are called namespaces
find the message incomprehensible and ignore it.

If the source document has a namespace declaration then it changes the names
of the elements, and if your stylesheet is trying to match elements by name
then they won't match unless you get the namespace right. So understanding
this is absolutely fundamental.

Michael Kay
Saxonica

> On 23 Jul 2020, at 21:55, Manuel Souto Pico terminolator@xxxxxxxxx
<xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> I think I can answer myself.
>
> The stylesheet needs to have the version hardcoded in the root element, at
least from what I can tell, like
xpath-default-namespace="urn:oasis:names:tc:xliff:document:1.2", and it must
be the same version as the input XML files.
>
> Cheers, Manuel
>
> Manuel Souto Pico <terminolator@xxxxxxxxx <mailto:terminolator@xxxxxxxxx>>
escreveu no dia quinta, 23/07/2020 C (s) 21:11:
> Dear all,
>
> This transformation gives me an empty output file:
https://xsltfiddle.liberty-development.net/gVhEaiQ
<https://xsltfiddle.liberty-development.net/gVhEaiQ>
>
> However, if I remove the xmlns="urn:oasis:names:tc:xliff:document:1.2 bit
from the XLIFF root node, then it works.
>
> Could somebody help me understand why that happens?
>
> Thanks in advance.
>
> Cheers, Manuel
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