Re: [docbook-apps] WARNING: cannot add @xml:base to node set root element. Relative paths may not work.

[Alexey Neyman <stilor@att.net>]

Hi Lars, Bob,

Just one point: xsltproc does xml:base fixup on nodesets included through 
XInclude, so inside the document there are xml:base elements added properly. 
However, Bob's point still stands: if the top-level document is in non-current 
directory, it will break the external references.

Speaking of Saxon, I am not sure if it does xml:base fixup properly on 
XIncluded modular documents from different directories. Originally, I was 
investigating a bug in libxml2 regarding xml:base fixup (pushed to master, 
will be in the next release), but I also tried Saxon. Here is a link to the 
thread on libxml2 mailing list (which has a small test case attached):

  https://mail.gnome.org/archives/xml/2013-April/msg00024.html

In brief, Saxon seems to emit xml:base relative to top-level document rather 
than to the most recent point of inclusion. DocBook stylesheets (at least, 
1.78.0 that I used) assume the location relative to the base of the including 
nodeset. xsltproc conforms to the expectations of DocBook stylesheets, and as 
far as I understand, to the XInclude specification.

Regards,
Alexey.

On Tuesday, May 14, 2013 09:01:37 am Bob Stayton wrote:
> Hi Lars,
> You should get that message only when two conditions are met:
> 
> 1.  You are processing a DocBook 5 document with the non-namespaced
> stylesheets. or
>     You are single-step profiling by using profile-docbook.xsl (probably
> your case).
> 
> and
> 
> 2.  You are using xsltproc (which lacks an extension function to get the
> name of the current directory).
> 
> With either condition in (1), the document is preprocessed into an internal
> nodeset (a nodeset held in memory) before being processed by the
> stylesheets.  The internal nodeset loses all contact with the filesystem
> where the files originated, so the preprocessing template tries to add
> relative directory references into the internal nodeset by adding xml:base
> attributes to preserve the relative locations.  It uses an extension
> function to get the original base directory of the document, but xsltproc
> does not have a function to fetch that information, while Saxon and Xalan
> do.
> 
> So if you use modular doc and the modules are in various directories, that
> directory structure  information gets lost in the internal subset.  If
> your documents don't need such xml:base attributes, then it has no effect
> on your output.
> 
> You can avoid it by either using Saxon, or by using two-step profiling.
> 
> Bob Stayton
> Sagehill Enterprises
> bobs@sagehill.net
> 
> 
> From: Lars Vogel
> Sent: Tuesday, May 14, 2013 7:13 AM
> To: DocBook Apps
> Subject: [docbook-apps] WARNING: cannot add @xml:base to node set root
> element. Relative paths may not work.
> 
> 
> Hello,
> 
> 
> since a while I get the following warning during the transformation with
> the docbook distribution:
> 
> 
> WARNING: cannot add @xml:base to node set root element.  Relative paths may
> not work.
> 
> 
> 
> I'm not sure what triggers this warning, a Google search resulted in hints
> about Docbook V5.0 but I'm still using Docbook 4.5.
> 
> 
> I'm currently using the docbook-xsl-1.77.1 distribution and I think (but
> I'm not sure) that I have this warning since I upgraded from 1.76. The
> output looks ok to me, but this warning does not create a warm fussy
> feeling. ;-)
> 
> 
> Any hint how to get rid of this warning?
> 
> 
> 
> Best regards, Lars