Re: A few questions about sgml

Tim Berners-Lee (timbl)
Thu, 24 Sep 92 15:51:46 GMT+0100

Date: Thu, 24 Sep 92 15:51:46 GMT+0100
From: timbl (Tim Berners-Lee)
Message-Id: <9209241451.AA23922@ >
Subject: Re: A few questions about sgml


Thanks for your mail.  It'll be great to see you documents on the web.

let me explain the relationship between SGML and HTML. As you probbly
know, when you use SGML, you must use a particular document type
(DTD). Our HTML is a particular document type -- it includes simple
formatting and hypertext links. We defined it because there was no standard
DTD for hypertext around (there still isn't).

So HTML is SGML but not necessarily the reverse.  If your documents are
in a different documen type then you can do one of two things:
one is to write a server which will take your SGML documents and convert
them into HTML (one th fly, probably) for W3 clients.  This will
probably mean translating some tags.

The second option is to wait until the format negotiation which we
are putting into the protocol comes out. This will anser your second
question too, in that it will allow graphics to be picked up.
The fact of life here is that there are no (or rather, too many)
standrads both for SGML DTDs and for graphics (and sound, video etc)
so futur clients will be configured to know which formats you can
use on your local machine. They will tell the server this, so that the
server can send a document in the "best"format possible.  You could define
your own DTD as a specific document format, and define the software which
you will want to run to handle documents in that format.

Now in parallel wit these developments (the format negotiation runs in
prototype form now), Pei Wei of O'Reilly Assoiciates, the author of the
Viola browser, is putting in generic SGML handling (ie coinfigurable
for many different DTDs) as well as embedded graphics. So his browser,
also currently in prototype form, will do just what you want, I think.

Tim Berners-Lee

	From Wed Sep 23 22:42:59 1992
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	Subject: A few questions about sgml
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	  My name is Joseph Lappa and I work for the Pittsburgh Supercomputing Center. 
	We are currently evaluating information servers including WWW.  We have decided
	to write all of our documents in SGML and make them available to our users via 
	some protocol/server (WWW, wais, or gopher).

	I have a few questions (and I hope I'm asking the right person :-))

	1) Can WWW read in SGML directly into a document bypassing HMTL?  I was reading
	   one the in documents that SGML was very important to WWW but I'm not sure
	   where SGML fits in.

	2) Is there the capability to retrieve non-hmtl files such as GIF or CGM files
	   that are included within a SGML document.  We are very big on CGM file
	   format and our SGML file viewer allows CGM files to be included as figures
	   or even animations (this would be for viola and other graphic interfaces).  

	3) Do you plan on having a SGML text (like vt100 terminal) viewer in addition 
	   to a X-Windows version such as viola?

	I hope these questions make sense :-)

	Thank You very much,
	Joseph Lappa