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Re: Nostradamus (was Re: FO. lists as tables)


Subject: Re: Nostradamus (was Re: FO. lists as tables)
From: David Carlisle <davidc@xxxxxxxxx>
Date: Fri, 15 Oct 1999 15:45:40 +0100 (BST)

> Take TeX's line-breaking algorithm, for example. You can specify what
> it does in terms of its results: It breaks lines on a per-paragraph
> basis in such a way as to minimise the total number of "demerits" in
> that paragraph, where "demerits" has a precise mathematical definition
> (which I won't go into here).

I think that one of the main points about the dsssl/xsl-fo kind of
abstraction is that it allows a formatter neutral specification of
style. If you were to enforce things down to the level of line breaking
then essentially you would only ever have one formatter available.
(You could build another one, but why bother if it was forced to give
the same results.)

For example TeX isn't a bad formatter, but it isn't perfect, but if the
algorithm specified for XSL-FO wasn't _exactly_ TeX's (for instance, if
it had improvements like being able to limit runs of consecutive
hyphens, or to hyphenate the first word of a paragraph, or to be able to
dynamically change the shape of a paragraph depending on insertions or
page breaks or...) then it would be impossible to use TeX as a back end
for XSL.

You can write a style specification in dsssl today and run your document
through jade and then the document comes out with that style applied in
a somewhat related manner in MSWord, in TeX, or in Frame. This is a
useful feature. I don't see how you could possibly specify that these
three different systems make the same line and page break choices, so
it seems the only way to ever get a standard that specifies things down
to that level would be to not use any existing formatters and only allow
(new, and a possibly unique) formatter that was written to the spec.

Of course if you are writing a book, you want to make sure that you, and
your final typesetter are using the same xsl formatter so you get the
same results, but then the fact that other people, or you later, can use
the same style specification and format the work in a different system
or for a different media seems like an advantage rather than a
disadvantage of XSL.

David


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