Re: [xsl] XSL-FO versus PostScript

Subject: Re: [xsl] XSL-FO versus PostScript
From: David Carlisle <davidc@xxxxxxxxx>
Date: Fri, 28 Feb 2003 22:09:10 GMT
> Modulo limitations in the XSL 1.0 spec, a good FO implementation should 
> be able to produce results comparable with TeX (and of course, there are 
> two TeX-based FO implementations, Sebastian's

well sebastian's is written using the xmltex parser and element matching
system implemented in TeX (by me) so I know something about that one:-)

> possibly even leveraging existing TeX-based MathML processing.
well not surprisingly passivetex supports mathml. In fact xmltex just
loads support files on demand as it hits each namespace so you can
freely intermingle html docbook tei and mathml and it'll do something
more or less sensible (not that I recommend that:-)

>  but there's no *inherent* limitation in the ability of FO-based 
> systems to produce typographic results as good as those produced by any 
> other system.

Actually I disagree. XSLT inherits from DSSL implementations a lack of
feedback from the typesetter to the rest of the system.
this means that there are some things you just can not do without some
non standard extension. In latex I have (in FO speak) a formatting
object for a table layout that goes something like
if it fits, put it here
otherwise try it in landscape,
 if it doesn't fit that way either reduce the font size
If it fits on one page make it into a floating table
otherwise tyeset it here as a multipage table, possibly landscape.

You just can't do that with FO as FO doesn't have the vocabulary to
make the tests and the XSLT stage before the FO doesn't have the
information about rendered size.

That example is a bit extreem but even the bog standard latex figure
table captioning formatting object isn't available in FO
which says roughly typeset it one way if it will fit on a line,
otherwise typeset it slightly differently as a displayed paragrah.

Then there's a whole raft of issues about references to page numbers etc
only known at formatting time. references to "on this page" etc.
I think you've commented on these before.
All of these are standard with something like latex (and easy to achieve
because of its tight integration with the formatter, although as I
commented before this comes at a heavy price: tight integration with a

> To that degree it's not even meaningful to compare XSL-FO 
> (or TeX) and PostScript.
yes agreed that's why I said it was apples and oranges in my initial
post on this thread.

> The value of XSL-FO accrues from its generality and abstraction,
total agreement here.

> at the cost of some limitations in 
I'm a bit confused here because I seem to be agreeing with your whole
message including this bit, which seems to not agree with teh "inherent
limitation" qute above, unless you mn that these feedback issues could
be fixed in a revised spec?


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