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From Peter Hargreaves <>
Subject Re: Documentv20 --> DocBook
Date Tue, 30 Dec 2003 01:34:58 GMT
On Mon, 2003-12-29 at 22:37, Ross Gardler wrote:
> Peter Hargreaves wrote:
> > The following is to strengthen the case for DocBook (or some other media
> > independent DTD) as the central document type.
> > 
> <snip what="points 1-4 saying we need a generic media independant format"/>
> > 4) The skin should be the very first time that presentational, layout
> > and target media languages (such as XHTML, fo, WML, PDF, DOC,etc) are
> > used.
> True.
> XHTML doesn't contain presentational information. It does guide 
> presnetation, but it doesn't dictate it. It is the final rendering into 
> the target media language that has the actual presentation information 
> (such as XHTML+CSS, note the '+CSS', PDF, DOC etc.)

Maybe the subset of XHTML adopted for Forrest could be a media
independent DTD like DocBook is.

What do you mean by presentational information? For me
<header>...</header> or <footer>...</footer> would be presentational
information because its meaning is about layout, and it assumes a media
type like paper that has headers and footers. However,
<title>...</title> is not presentational because its meaning is not
about layout. The skin or style sheet for the media called paper can
choose to put a title in the footer of the page or in the header.

> Just because it is called X*HTML* doesn't mean it has to be rendered in 
> a browser.

No, but if it is inspired by the real XHTML spec then it will be
particularly suitable for a subset of final client types - and might not
be so suitable for others.

> > 5) Some legacy source content DTDs are derived from target media
> > languages but they need not influence the choice of central DTD.
> True, but the XHTML Vs Docbook discussion has been had many times in the 
> past, my original post was prompted because I have been reading the 
> archives alot lately and whenever XHTML Vs Docbook xomes up XHTML seems 
> to win out. For good reasons, lets see if it still does...
> <snip what="pints 6-7 saying docbok is media independant and 
> semantically rich"/>
> > 8) A central document type, standing between content and skin, must not
> > filter out richness of meaning of document structure, or it will
> > undermine the presentational possibilities.
> I have recently been conviced that at the forrest intermediate level all 
> the semantic information I *thought* I needed is actually presentational 
> information (see 
> As a result it can all be captured in the class attribute. How it is 
> presented is then up to the rendering engine, which is exactly what 
> should happen. I have to admit, I was suprised to find that I ended up 
> agreeing with this view, but agree I did once I tried to justify my case 
> with what I thought were rock solid use cases!
> > 9) A central document type must therefore be very rich in its
> > description of document structure and meaning - without bias toward
> > media type.
> Quite the reverse. It should be as simple as possible, semantic meaning 
> has no place at the presentaional layer, it is only presentation that is 
> important.
If its simple then it will undermine the meaning of the original markup
- so the final presentation will be limited.
> Can you give us a use case in which we need semantic meaning at the 
> intermediate stage in order to do anything *other* than effect how the 
> data is presented.

Of course ALL markup meanings at the intermediate stage can be used to
affect the final presentation. But their meanings should not be about
presentation or layout, So, role="MSc" is OK but align="right" is not.
The skin stylist should decide left or right and in any case the target
media might not have a left or a right. e.g. Audio.

> (He He, this is exactly what Jeff asked me to do and I thought I could 
> do it, now I'm a convert - ex-smokers are always the worst :-)).
> > 10) The central document type might be user chooseable, if Forrest can
> > cope with the complexity of this?
> Interesting... what would Forrest gain from this? We have user 
> selectable source formats, isn't that what is important from the user 
> perspective?
> Having said that, you can easily change your local xmaps in order to use 
> a different intermediate format for certain documents if you find the need.
> > For those not familiar, here is an extract from Norman Walsh's DocBook:
> > The Definative Guide:
> > "DocBook provides a system for writing structured documents using SGML
> > or XML. It is particularly well-suited to books and papers about
> > computer hardware and software, though it is by no means limited to
> > them. DocBook is a document type definition (DTD). Because it is a large
> > and robust DTD, and because its main structures correspond to the
> > general notion of what constitutes a book, DocBook has been adopted by a
> > large and growing community of authors. DocBook is supported “out of the
> > box” by a number of commercial tools, and support for it is rapidly
> > growing in a number of free software environments. In short, DocBook is
> > an easy-to-understand and widely used DTD. Dozens of organizations use
> > DocBook for millions of pages of documentation, in various print and
> > online formats, worldwide."
> For me this indicates it can be used as a source format, but not as an 
> intermediate format. The key phrases for me are:
> "particularly well-suited to books and papers about computer hardware 
> and software"

"though it is by no means limited to them"

> and
> "its main structures correspond to the general notion of what 
> constitutes a book"

Ah, excellent point! Note that "book" has two meanings:

1) The media type called book. I.E. a blank hard back with a binding and
blank white pages.

2) The content type called book. I.E. a novel or work of reference that
may or may not be delivered via the media type called book.

> - I use forrest for training materials. Docbook *could* be used as a 
> source format but it is not ideal in my domain. I use other formats as 
> my source that have been designed for the purpose. By converting to 
> docbook as an intermediate format I will be losing semantic information, 
> which is something you say I shouldn't do, but something I am now 
> comfortable with (see above).

When an author writes a document or book using a DTD that is truely
media independent - he will have no control of style, layout or
presentation and should not think of such things. His document might be
delivered through any of many different style sheets for each of many
different media types. So, for the author, the cost of delivering
content to many media types is that he can no longer use style as part
of his message.

> My point is, *no* (usable) intermediate format will be so expressive 
> that it can accomodate all users.

Quite. Equally true for whatever intermediate DTD you choose.

> On the XHTML side of things, the following text from the XHTML working 
> draft convinces me that XHTML should be the intermediate format:
> "The XHTML family is designed with general user agent interoperability 
> in mind. Through a new user agent and document profiling mechanism, 
> servers, proxies, and user agents will be able to perform best effort 
> content transformation. Ultimately, it will be possible to develop 
> XHTML-conforming content that is usable by any XHTML-conforming user agent."

Yes, an excellent and interesting point. But, hasn't XML sort of
displaced this approach to some degree? Maybe it will catch up again?

XML is designed for XML > FO > PDF for instance. But if you try to do
XML > XHTML > FO > PDF you screw it all up.

> If I am going to lose some semantic information I want to be sure that 
> the language I am using is so generic that I don;t lose any 
> presentational information regardless of the media type. That is what 
> XHTML is designed for.

I think I've answered this one.

> Am I making any sense?
> Ross

Yes lots of sense - good discussion - interesting points.


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