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   Re: Topic Maps on SQL

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  • From: "W. Eliot Kimber" <eliot@dns.isogen.com>
  • To: xml-dev@ic.ac.uk
  • Date: Tue, 24 Nov 1998 11:13:51 -0600

At 10:40 PM 11/21/98 -0600, len bullard wrote:

>Steve brings up the point that I do wish would be looked at 
>seriously by other language communities:  the potential of 
>using property set/grove concepts to create information 
>standards that are independent of lexical/syntax representation 
>and implementation.  

While I agree with the general sentiment and certainly agree that groves
are a useful and powerful abstraction for talking about and working with
data, I'm not sure if it's appropriate to push property sets as the
definitional mechanism.

This is because property sets are, by design, a relatively simple mechanism
for data model definition. They do what we needed for HyTime and DSSSL and
no more. This is their strength (relative simplicity) but also their
weakness, for there are many things they can't do.

This is why we are pursuing the harmonization of STEP's EXPRESS data
modeling language with SGML's grove idea.  We are close to having a
fully-cooked definition of the semantic mapping between the fundamental
constructs defined by the STEP standard (entities with attributes in a
traditional data modeling sense) and those defined by the grove approach
(nodes with properties). We have demonstrated to our satisfaction that
there is such a mapping and that it is useful.  We have created draft data
models reflecting the SGML property set, the HyTime property set (linking
and addressing information), and a property set template for generating
property sets from EXPRESS schemas.  We expect to have these solid enough
for public consumption early next year.

Given such a mapping, it becomes possible to use the full descriptive power
of EXPRESS (or it's non-standard equivalents like UML) to define abstract
data models and then *automatically* generate the property set needed to
define the grove view of that data abstraction.  We're focused on EXPRESS
because it is a standard, but there are existing mappings from EXPRESS to
commercial products and proprietary languages like UML.

This gives you the best of both worlds: a complete and powerful modeling
language, divorced from any syntax, coupled with a standardized data
abstraction optimized for the "document processing" domain.  In short, you
can eat your data model and have your grove.

The "STEP and SGML Harmonization" work (really STEP<->grove) is being
conducted as a preliminary work item under ISO TC184/SC4, the committee
responsible for the STEP family of standards (ISO 10303).  This work has
formal liaisons with both the W3C (in particular, the schema working group)
and with ISO/IEC JTC1/SC34, the SGML family of standards).  There are two
mailing lists, one for information and one for ongoing work, that anyone
with an interest can subscribe to.  The results of our formal committee
work is posted on the STEP web site, <http://www.nist.gov/sc4>.

We are in the process of writing up our findings for wider publication.
Expect to see documents available in February, soon after our next official
meeting (Last week in January in San Francisco).  If anyone is interested
in participating in this work or tracking it, feel free to contact me for
more information.


<Address HyTime=bibloc>
W. Eliot Kimber, Senior Consulting SGML Engineer
ISOGEN International Corp.
2200 N. Lamar St., Suite 230, Dallas, TX 75202.  214.953.0004

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