Re: SGML objects

Bob Stayton (
Tue, 17 Aug 93 16:01:44 PDT

> From: Dave_Raggett <>
> > I've heard several people asking for nested section
> > containers in HTML+. Could one of you please explain
> > how you would break up a very large hierarchical
> > document into small enough file pieces to be
> > useable over the Internet? How would each file
> > piece be marked up?
> The answer can be looked for in Charles Goldfarb's SGML Handbook.
> You can declare an entity reference to an external SGML file and then
> "include" it. You can also make references to data stored in an external
> format using the NONSGML and NOTATION keywords. There are mechanisms for
> "public" identifiers (similar to URNs but run by the ISO and probably
> unsuitable for widespread use in the Internet), and "system" identifiers
> supposedly for local files. The "proper" SGML approach forces you to declare
> all such references and to then use local names in subsequent markup. HTML of
> course flouts this by including the URL directly in the elements defining
> hypertext links.

I don't understand how this addresses the problem
of delivering a large hierarchical document in HTML+
chunks. Are you suggesting that I create a "master"
document that contains entity references to the nested
sections, each of which could be in a separate file? If I
access the master document, would the entities be resolved
and all the content pulled in for viewing? (Do any HTTP
servers do that?) If so, that is the same as pulling across
the whole book.

Also, the external files would not each be parsable SGML,
right? They would be SGML fragments because their parent
section containers would be in the master file. So they
couldn't be accessed directly. I'm looking for random
access into pieces of a large document.

Nesting section containers is great when you are working
with the whole document. But it seems less desirable
in a modular system like WWW. SGML doesn't require
nesting section containers, although it is the most
common way of representing hierarchical information.
I'm hoping the hierarchical relationships between sections
can still be encoded in SGML, using a flatter style of
DTD like HTML.