Path: utzoo!dciem!trigraph!les
From: les@trigraph.UUCP (Les Gondor)
Newsgroups: comp.graphics
Subject: Re: need descriptions
Message-ID: <427@trigraph.UUCP>
Date: 25 Nov 88 16:35:39 GMT
Article-I.D.: trigraph.427
References: <3270@entire.UUCP> <1665@hp-sdd.HP.COM> <1988Nov16.234857.2372@cs.rochester.edu> <1679@hp-sdd.HP.COM>
Reply-To: les@trigraph.UUCP (Les Gondor)
Distribution: na
Organization: Trigraph Inc., Toronto, Canada
Lines: 79

In article <1679@hp-sdd.HP.COM> andrea@hp-sdd.UUCP (Andrea K. Frankel) writes:
>In article <1988Nov16.234857.2372@cs.rochester.edu> ken@cs.rochester.edu (Ken Yap) writes:
>:|There is an ISO standard SGML (Standard Graphics Markup Language) which
>:|isn't exactly a printer description level, but a metalanguage in which
>:|one can describe many different kinds of output languages.  You can buy
>:|SGML from ANSI in New York.
>:
>:Er, isn't this Standard Generalized Markup Language? As I understand,
>:it is a system for defining conventions to be used for the transmission
>:of marked-up documents. For instance, a tag like <q> can be defined to
>:mean "start of quoted text". It is not a typesetting language. A SGML
>:document can be turned into formatter input via a translator. SGML
>:definitions are intended to be at a higher level of abstraction than
>:formatter directives.
>:
>:I shouldn't say more because I'm not an expert. The experts are on
>:comp.text.
>
>My understanding is that there are simultaneously two types of organization
>in SGML - logical and layout.  The former allows you to specify things like
>sections, chapters, subsections and so forth that pertain to the logical
>structure of the contents.  The layout talks about how text flows onto
>the page, what a paragraph looks like, what kinds of things you do at
>start of section/chapter/etc.  Taken together, you can transmit in SGML
>a pretty detailed description of your document and how you want it to look,
>at which point the recipient can translate it to troff, PostScript, or
>whatever language the typesetter uses.  

Er, not really.  SGML deliberately avoids layout issues and
concentrates instead on how one describes a syntax for 'marking up' the
logical structure of a document.  It says what logical entities (and
what are their associated markup tags) can appear at a given point in
the document and what attributes are associated with the tags.  It is
only when an external entity associates layout actions with those
logical tags that one can talk about layout, but that is outside the
intended scope of activity of an SGML parser.  In the ideal world, the
document markup would be purely structural, as opposed to being
concerned with the layout or formatting and SGML goes a long way to
enforcing this separation of form from content.

The association of layout design with the logical structure of a
document is the subject of another ISO standard going by the acronym
DSSSL (Document Style, Semantics and Specification Language).  I have
yet to see the working draft of this standard, but it is coded in SGML
(presumably, agreed-upon attribute names are used to describe the
layout).  I speculate that one can then link tags defined in the
logical document description to those defined separately in the style
and then go on to lay out the document.

A related standard is ISO 8613, Office Document Architecture, which
does define a transmission standard for multi-media documents that
incorporates both logical and layout information in the same stream.
Part of this standard defines an SGML encoding of this stream.

>...  It seems to be mentioned more frequently by Europeans than
>Americans, although I don't have any real data on relative availability
>of implementations.

SOBEMAP, Datalogics and SoftQuad all sell commercial implementations of
SGML applications.  NBS through the NTIS provides source for an SGML
parser.  E-mail me if you want more info.

>
>At any rate, the SGML folks I've talked to are confident that SGML
>documents can be translated into just about anything that has enough
>positioning control and the right fonts, so it doesn't appear to be a
>standard that graphics folks need to worry much about (yet?).
>
>Andrea Frankel, Hewlett-Packard (San Diego Division) (619) 592-4664
>Internet : andrea%hp-sdd@hp-sde.sde.hp.com (or @nosc.mil, @ucsd.edu)

There appears to be at least one paper on graphics and SGML, although the
reference I have indicates that it is in preparation: "An SGML Application
for Graphics", C. O'Connell, S.A. Mamrak, R. Parent (to appear in CG&A).

-- 
Les Gondor, Trigraph Inc.	"Why not just do it by knife?"
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