Well, you can define whatever tags you want in SGML, so I'm not sure what
you mean by `available in SGML'. It sounds as if you want to use DD/DT
to get parallel columns of text, not just a way of defining terms in a
glossary. A poor man's table, if you will.
I think that DD/DT are used for 2 or 3 main things:
* tagged paragraphs, which are essentially like list items where you
can specify what the tag is, e.g. for marking up lists of people who
are going to attend, with a desctiption of each, or for a feature list;
* a way of getting pretty bullets (superseded in HTML 3)
* a way of getting indented text, as in the GNN what's new page.
You could think of the 2nd purpose as being a subset of the first.
Some browsers display the <DT> and <DD> in two columns, and some don't,
and it doesn't actually make much sense to have two headings, I think, for
a definition list; however, the ability to have 2 or more parallel columns
of text, rather like a table without borders, is certainly useful.
Why not use a table?
* might be harder to generate automatically
* might be more complex to tag, especially if you are doing it `by hand'
(i.e. not using an HTML-aware tool that gives table support)
* tables aren't supported everywhere -- clearly not a reason for proposing
another and necessarily even less widely supported feature!
* some implementations of tables don't support
. nested tables
. multiple paragraphs in a table cell
. specifying left/right/centre justification on a table column
* it's further away from the logical structure of the document
Of all of these, the last reason seems to me the only one worthy of adding
a new feature. Multiple parallel columns are no harder to implement than
fixing (or adding support for) tables to allow markup in them.
Lee
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