Re: DTD - any info about them

["Simon North" <north -at- synopsys -dot- COM>]

Hi Debbie, 

A DTD is essentially a data model for your SGML information in the 
same way that a database structure is. The DTD should reflect 
what you want to do with your SGML data. Ultimately, just as with 
a database, you can only get out what you put in (if your smallest 
element is a section, that will be the smallest unit you can deal 
with). You should therefore choose, or write, your DTD very 
carefully or the results will come back to haunt you time and time 
again. 

There are hundreds of DTDs 'out there' ranging from the incredibly 
detailed (TEI), to quick and dirty (HTML) and attempts to be as 
universal as possible (DocBook).  Developing your own DTD, if you 
do it as it *should* be done, is a very long and complex task. 
Writing the DTD itself is pretty trivial, the effort goes into the 
surrounding design effort and things like documentation (you'd think 
people involved with SGML documentation would understand the 
need to document a DTD but it often doesn't happen ... and I'm 
guilty too). 

Based on my own experience gained from trial and error over the 
past 10 years or so, I'd advise you to use a commercially available 
DTD as the basis and tailor it to your needs. Most (J2008 and 
DocBook are good examples) are specifically built to allow you to 
customize them. 

There is one big argument in favor of DocBook, there's already an 
implementation built into Frame+SGML. You should be aware that 
having a DTD is one thing, but to make it usable in Frame+SGML 
you will also have to create the Frame application (which is almost 
as much work). 

The following links is probably the most useful source on DocBook:

http://nwalsh.com/docbook/index.html

and there is a substantial collection of DTDs at:

ftp://info.ex.ac.uk/pub/SGML/

The definitive book is Developing SGML DTDs: From Text to Model 
to Markup by Eve Maler, Jeanne El Andaloussi, Prentice Hall; 
ISBN: 0133098818. 

I hope this at least gets you started.

Regards, Simon North
Tech Writer, Synopsys
"Teach Yourself XML in 21 Days" (which also describes DTD 
development).