RE: [xml-dev] DTD Design

["W. Hugh Chatfield I.S.P." <hchatfield@urbanmarket.com>]

I think you meant "limits the number of levels of subsections" ... not the
number of subsections.

You can either define

 1.a section to be recursive (sections can contain sections at the next
lower level)
 2.a section can contain a subsection which can contain a subsubsection
which can contain a subsubsubsection  to whatever level makes sense to your
application.

Which is "better"?

1. infinite section recursion
     (dtd/schema)..fairly simple .. one element for any number of levels
     (authoring) no limit to depth author can use... no obvious depth
indicator.. everything is a section no matter what level you are at... this
might be a problem in some environments
     (publishing)at some level you will hit problems... if each section at a
lower level is indented "x" cm, then clearly you will eventually run off the
page eventually... so you will normally allow for n levels in any of your
code... beyond which something breaks.  Usually hard to prevent except by
"convention".

2. fixed number of named levels
     (dtd/schema).. only slightly more complex.. one element per level..
probably each element having the same model
     (authoring) .. author knows level in document explicitly by name.  The
names you give these structures might be mirrowed by normal use by humans..
so there is no confusion (a legislative problem I worked on, named each
level of text explicitly and legal authors legislators normally referred to
these levels by these names)
     (publishing).. layout can be predefined for fixed number of levels

The transformation into html/xhtml is pretty simple for either.

So I guess the answer is ... it depends on your problem.

For the one problem I mentioned above.. it was natural to use the names for
the levels that the people used in day to day activity... and it allowed
tight control of the overall structure. (142 pages into a legal text .. who
can tell what level you are at.. it was nice to know you couldn't go any
more than 8).

If you really need a variable number of levels... then recursive sections
will avoid the "yes I know there are 12 levels allowed... but I need 13 by
tomorrow" problem (except for publishing problem).

Cheers...Hugh

W. Hugh Chatfield  I.S.P.
CyberSpace Industries 2000 Inc.
XML Consulting & Training
http://www.urbanmarket.com/csi2000
See also:  http://www.all-about-perth.com




-----Original Message-----
From: Morcom, Harvey [mailto:Harvey.Morcom@KPMG.co.uk]
Sent: Wednesday, November 20, 2002 9:51 AM
To: 'xml-dev@lists.xml.org'
Subject: [xml-dev] DTD Design


We are in the early stages of moving our existing information into XML and I
am starting to look at the DTD and was after some advice.

It was initially proposed that we use the format SubSection(n), however this
limits the number of  sub-sections the document can have. I proposed the use
of a generic section element which will remove this. Which approach is
better? What are there strengths/weaknesses? DOCBook which uses nested
section elements states 'Use of deeply nested Sections may cause problems in
some processing systems.' ?

The documents will be displayed via a browser using XSLT to convert the XML
to HTML.

Thanks in advance

Harvey



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