Renderers and XSL-FO, plus other thoughts...

Hi, all

I'm interested in soliciting comments regarding interfaces for XSL-FO processors, and the possible use of FO as an interchange format irrespective of the existence of FO processors.

Let us define the software that accepts FO as input, and produces a formatted area tree (as stipulated by the XSL specification) as output, as a "formatter", for the sake of this discussion. It seems to me that "renderers", that is, translators from area-tree information into print-quality output formats, would (should?) be restricted to stuff like PDF, PostScript, and the like. That is, _rendering-level_ translation happens at the back-end. And it happens with formats that can support the goals of the original FO, not with HTML or RTF.

My feeling is that there is nothing to be gained by having, say, an RTF "renderer", since the real correspondence is between the FO (XSLT result tree) at the formatter front-end and RTF, not between the formatter _output_ and RTF. That is, _formatting-level_ translation happens at the front-end.

What are the opinions on this division? I think it is reasonable.

Related issue: pros & cons of using FO as a common interchange format for formatting "languages"? I have no strong feelings either way, but the possibility is there. Advantage being is that it would be XML, and hence easily processed by ubiquitous and reliable tool sets. It would also be a relatively high-end interchange format, arguably better than CSS even in its latest incarnations. Comments?

HTML or WML or HDML? Don't even think of these and FO in the same breath. :-) Just my opinion - WML/HDML, and placing useful content on handhelds and cellphones, is my real job, and I think XSLT does just fine. Using either FO or CSS (and the CSS people are definitely targeting handhelds) for phones or PDAs makes little or no sense.

Final thought: do users believe that formatter flexibility in also accepting CSS would be a boon? The formatting model is shared (in theory) between CSS and XSL-FO. A formatter that accepts CSS-styled XML could present pretty much the same formatting-object tree to the formatter as we get through FO. Or so goes the possible argument. Is consideration of this worthwhile? What do people think?

Food for thought. :-)

Regards,
Arved Sandstrom