xml-dev - Re: xslv updated

[Sebastian Rahtz <sebastian.rahtz@computing-services.oxford.ac.uk>]

Rick JELLIFFE writes:
 > But nothing anywhere actually specifying any hard details. What features
 > are missing from XSL-FO?  Perhaps Sebastian could give some details: I
 > for one would find it useful to have some idea of what is missing or
 > where they have gone wrong. 

Following DSSSL, they decouple the stylesheet from the
formatter. Which makes it impossible to implement 

 1) a design which says "captions are centered unless they are longer
    than one line, in which case they are ragged right"

 2) a cross-reference system which says "figure 1 on the opposite
    page" or "figure1 on p.56", depending on where it floats to

two things which are easy enough to do in LaTeX (to take a typical
benchmark)

 > built under XSLFO. From vague memory, it seems that the biggest design
 > decision is whether to follow FOSI (an old DOD stylesheet language
 > written using instance syntax which allowed expressions to query the
 > current page position: this required tight coupling with the formatter
 > so only ArborText really implemented it) or DSSSL (keep a layer above
 > the breaking routines/paginator; sacrificing the ability to test current
 > page position forces more declarative nature {e.g."keep-togethers"},
 > reduces expressiveness, sharply increases retargetability.)  

You express it excellently. FO follows DSSSL in the reduced
expressiveness. So that stops you implementing the highest quality.

 > vary for the material used too: for typesetting yellow page telephone
 > books (i.e. with display ads), according to one contact it is difficult
 > to get a good result without 4 page lookahead for determining which
 > pages floats should go on.  I would not expect XSL-FO to provide someway
 > of setting the lookahead for optimum page-floatation: that should be an
 > implementations decision for vendors to diferentiate their products.

But if the XSL cannot talk to the formatter, how can it base other
style decisions dependent on what the page floating came up with?

Sebastian Rahtz


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