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Subject:What is SGML From:Charles Cantrell <chc -at- ONTARIO -dot- COM> Date:Thu, 26 Mar 1998 10:18:35 -0500
Steve,
This is not a simple question. SGML stands for Standard Generalized Markup
Language. It is a "programming" language for describing a document
definition structure. For example, HTML is one such structure that conforms
(mostly) to an SGML format.
With SGML, one defines a DTD or document type definition that defines the
"tags" or structure of the document. For example, in HTML, you must have
<HTML><HEAD></HEAD><BODY></BODY></HTML> tags, in that order to have a well
formed document. (Of course, if that is all you have, it is a nil file.)
But, where other types of DTDs differ from HTML is that they do not need to
be "appearance" based tags. They may be, instead, functionally defined. For
example, you could define a "part number" tag, which would be a part of a
"product" tag. So, if you had
<PRODUCT>Widget
<PARTNUM Num="102394">
<DESCRIPTION>The widget is a black oval plastic shape which fits smoothly
in the hand and causes soothing sensations to the digits.</DESCRIPTION>
....
</PRODUCT>
Your product could be stored in a database, and people could search for all
products that included, for example, the word soothing in the product
description.
You could then use a programatic tool to display just the documents, or
parts of documents that met their search criteria.
The pros of SGML are database storage, on demand delivery, reusability of
document parts, "lights out" publishing of the documents, and a number of
ones.
The cons are severe learning curve, high costs of database storage, SGML
tools, and writer acceptance.
If you are interested, Liora Alshuler's book, ABCD...SGML is a good
introduction to the uses and environment of SGML. It is not, however, a
tutorial on SGML. It will not teach you to write a DTD. However, that is
most often done by your SGML vendor.
>Can anyone explain to me the whys and wherefors when it comes to SGML.
>
>What can I gain by using SGML to describe my documents?