[xep-support] XSL and Relax NG

[Nikolai Grigoriev]

Hi Gustaf,

> I hope there will be a Relax NG validator (supporting normal and
> abbreviated syntax) included in XEP one day. Perhaps XEP error 
> reporting would come closer to the intentions in the standard (since 
> the standard can't be expressed with a DTD) with a fo.rng file? 
> Do I overlook something? What about the XSLT processor?

Relax NG is a good schema language; some day, we  plan 
to develop a RNG schema for XSL FO. However, what we 
have in XEP 3 appears to be a simpler, cheaper, and more 
powerful alternative to a schema language: a Schematron-like 
XSLT stylesheet. (It is written from scratch, not generated by
Schematron). To see it, go to the lib/ subdirectory of XEP root
and type the following:

  jar -xf xep30*****.jar com/renderx/xep/folint.xsl

(xep30*****.jar should be XEP's jar name). Inside XEP,
we simply apply this stylesheet to input data, and collect 
<xsl:message>s generated. 

> What happened to fo.dtd by the way? Haven't seen it in XEP 3...

Yes, we dropped it from XEP distribution because it is not used
any more. It is still available from our site, and all new extension 
elements introduced in XEP 3 have found their way into it. 

I believe that a schema for XSL FO (DTD, RNG, or WXS) is
indicated for structured editors. For pure formatters, the task 
is much simpler: we only have to check input correctness, 
and don't need to figure out the overall document structure.
A schematron-like approach seems more appropriate for 
the task, because: 

- it poses virtually no limits on types of situations that 
  can be checked - XSLT is orders of magnitude more 
  powerful than any schema language;

- it gives a far better control over error reporting.

Best regards,
Nikolai Grigoriev
RenderX






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