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Re: `High-level' format specifications with XSL?

Subject: Re: `High-level' format specifications with XSL?
From: Paul Grosso <paul@xxxxxxxxxxxxx>
Date: Thu, 2 Jul 1998 10:52:07 -0400
At 09:42 1998 07 02 -0400, Kai Grossjohann wrote:
>The information on how a heading is formatted is where?  I want to
>produce good-looking output without having to think about this
>myself.  Just like with LaTeX.  Is there a Good-Looking-HTML-with-XML
>XSL stylesheet out there?

Sharon Adler used to say about DSSSL is that this is where the rubber
meets the road; SGML/XML does the "easy stuff," but DSSSL/XSL is where
you have to get down to saying what it all really "means" (at least in
terms of presentation).

XML is the high-level markup--which is far from "just like LaTeX," but 
this is a better parallel in your case than XSL.  XSL is more like a LaTeX 
.sty file where you get to say just what things look like.  And if you've
written a few LaTeX .sty files, you know you have to "think about it."

In other words, the whole point of a stylesheet is to be able to specify 
what "good-looking output" should look like in your opinion.  You (or 
whoever writes a stylesheet) *has* to think about it.  If you don't want 
to think about it yourself, you don't want to write a stylesheet.

>I would be happy with a way to produce HTML with the usual <H1> and
><H2> as well as <DL>, <UL> and <OL>.  You know, the stuff that has
>been in HTML since version one.

Here, it sounds like you're talking about producing HTML, not assigning
style to XML.

Admittedly, this is a confusing part of what's called XSL.  XSL is developing
into a language that can specify a "stylesheet" that can do one of two things
(that is, any given "stylesheet" can only do one of the two):

1.  Specify how to map an XML document into a structure of formatting objects 
    with formatting properties that is meant to drive a composition process.
    This is the process I assumed in the first part of my response above.

2.  Specify how to map one XML document into a second XML document.  In this 
    case, the result is "just" another XML document which is no closer to 
    having defined style *as far as XSL is concerned* than the original one.
    In this case, XSL is being used to specify a transformation, so the
    so-called "stylesheet" is really a "transformation specification."

Note that, for case 2, it is possible for the target XML document to use 
element type names and attribute names like H2 and UL and such; that is, 
the target XML document can be what is sometimes called "well-formed HTML"
which is a well-formed XML document that uses the HTML tag set.

HTML is not XML in (at least) one important way:  it is single tag set
(instead of a language in which to define tag sets) with mostly
pre-defined presentational expectations, so HTML-aware tools (aka browsers) 
can have built-in knowledge of how to present, say, an H2 or UL.  In
other words, there is no need for a stylesheet for HTML.  If you map
some arbitrary XML into a document using the HTML tag set, you are
piggie-backing on the pre-existing HTML style.  It is like someone
already wrote the html.sty file for you in LaTeX, so you don't have
to "think about it."

This is the basic reason that case 2, the transformation case, is sometimes 
confused with defining presentational style.  It doesn't, but if you use
the transformation capabilities of XSL to map your document into a tag set
with pre-defined presentational semantics, then you have finessed the issue
of having to write a stylesheet by transforming your document into a tag set
for which an implicit "stylesheet" already exists.

If you just want a way to produce HTML with the usual stuff, then XSL's
transformation capabilities should address your needs.  But the key power
of XSL is to go beyond HTML-level presentational capabilities and specify
stylesheets for all kinds of presentational semantics using the case 1
paradigm I mentioned above.  For that, you might have to think about it
if you want to create such stylesheets "by hand."  Of course, many of us
are hoping to provide stylesheet generating tools with user-friendly
interfaces that do as much of the thinking for you as possible.

 XSL-List info and archive:  http://www.mulberrytech.com/xsl/xsl-list

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