FW: [topicmapmail] ANN: Topic Maps Graph and API in XML

From: Graham Moore <gdm@empolis.co.uk> · Date: Wed, 27 Jun 2001 14:42:49 +0100

k42 provides a graph view of topicmaps as part of the k42 engine. The DTD
used is called TMV (Topic Map View) and can be accessed via the k42 topic
map server. The DTD is part of the k42 download. I'll post it somewhere
public to avoid people having to download it.

At the time of development I just saw it as nice way to give developers
access to topicmap data in a useful XML way - XTM is not useful for building
scalable applications. I'm sure we can all imagine the issues there!

Not only does this model provide a graph representation of Topic Maps by
being able to follow from one node to another. It provides a server that can
retrieve fragments of this graph from a processed topic map using TMQL. I
make this point as I see 2 standards activities that need to happen in
conjunction with TMQL.

1. A coming together of the graph DTDs, TMV and TopicMapGraph
2. a protocol for retreieving these fragments from a TopicMap Server.

Thus giving us a framework for distributed topicmap servers.

If you want more information on the notion and requirement for the
distributed topic form see the TMQL requirements document that I submitted
that talks about distributed result sets.

While I think TMV and TopicMapGraph are useful tools - they allow rapid
development of applications that deliver custom views of a topic map. I
think we must realise that they are tools not yet a definition of the model.
We have a process now at ISO for describing the model of topicmaps - i think
we do, and It is quite clear that the XML graph representation will fall out
of that work. So I see in that TMV and TopicMapGraph are contributors /
suggestions as to what the internal model will look like.

I think the levels that Steve and Michel have developed ties in nicely with
what has been discussed on the issue of APIs and the requirement for several
layers of API.

Right - I'm off to play with extending k42 to have a TopicMapGraph component
as well as TMV. And work out what the differences are.

cheers

graham

-----Original Message-----
From: topicmapmail-admin@infoloom.com
[mailto:topicmapmail-admin@infoloom.com]On Behalf Of Michel Biezunski
Sent: 27 June 2001 12:25
To: Topicmapmail@Infoloom. Com
Subject: [topicmapmail] ANN: Topic Maps Graph and API in XML

To all:

We announce the availability of two DTDs for
describing the Topic Maps Graph at
http://www.topicmaps.net (see details at the end
of this message).

We'd like to share with you the results of a couple of
thought experiments we've been doing recently.

In Berlin, Jonathan Robie asked a very good question
about Topic Maps, which we would like to paraphrase as
follows:

"If the XTM DTD is for interchanging topic maps, why
can't instances of the XTM DTD be directly queried
using XQuery to use whatever information the topic map
has to offer?"

Steve N. vigorously defended the idea that, while a
fully-processed topic map graph is queriable, a raw XTM
instance is not queriable without first transforming it
(and the topic maps that it includes by reference) into
a topic map graph.  But, later, Steve was troubled by
the sheer good sense of Jonathan's plea that, if you're
going to use several syntaxes to interchange a certain
information set, *at least one of them* should be
absolutely reflect the true structure of the
information, so that, for example, XQuery can be used
to access the information.  Why shouldn't there be a
syntax for interchanging fully-processed topic map
graphs?

Meanwhile, Michel B. continued to be troubled by the
fact that still there are still so few people who
appreciate the comprehensiveness and simplicity of the
structure of topic map graphs as proposed in
http://www.topicmaps.net/pmtm4.htm.  Michel wondered
whether modeling a topic map graph by providing an
interchange DTD for topic map graphs would help people
understand the nature of topic map graphs more easily.

Steve N. was taken aback by Michel's proposal, because
it resonated so strongly with the reasonableness of
Jonathan's plea.  It also occurred to him that, given
the right XML interchange structure for topic maps, no
special API would be needed in order to use a topic map
graph.  The simplest DOM API would be a perfectly
adequate topic map browser, if only the XML rendition
of a topic map graph would be designed in such a way as
to support the browsing of topic map information.

So, this is our report that we have written two very
different DTDs, both of which are theoretically for the
purpose of interchanging topic map graphs, or for
publishing ready-to-use topic maps on the web.

One of the DTDs, "simpleTMGraph3.dtd", is probably
pretty close to being the simplest and least redundant
way to comprehensively represent a topic map graph in
XML.  This DTD will be interesting (and brief) reading
for anyone who wants to know the structure of topic map
graphs, and who is already familiar with the DTD
formalism.  Every node is an element, and every arc is
also an element.  The arcs do all the referencing --
each arc references the nodes that, in the topic map
graph, appear at their ends.

The second DTD, "TMGraphAPI3.dtd", is more practical
and more complex.  Its instances contain much redundant
information.  The redundancy stems from the fact that
this DTD is designed to allow simple non-indexing DOM
applications to browse the XML instance as if it were a
topic map graph.  The structure of the document
instance itself constitutes an API to the information
contained in that instance.  Every element that
represents a node (such as a topic node) contains all
of the references to all of the other nodes that would
normally be connected to that node via the arcs.  For
example, in an instance conforming to TMGRaphAPI3.dtd,
each element that represents a scope node contains
references to all of its component topics, *and* each
of the elements that represents one of its component
topics *also* contains a reference back to the scope
node.  These mutual references allow the simplest DOM
applications to browse from node-representing element
to node-representing element, just as if these
applications were following the arcs of a topic map
graph.

DISCLAIMER: These DTDs have no official status of any
kind in any context.  We hope they will help to enlarge
the public conversation about the essential nature of
topic map information.

URLs:

http://www.topicmaps.net/index.htm gives orientation to the files below:

http://www.topicmaps.net/struct.htm : structure of topic map foundations
http://www.topicmaps.net/simpleTMGraph3.htm: a Topic Maps Graph, in XML
http://www.topicmaps.net/TMGraphAPI3.htm : an API to a Topic Maps Graph, in
XML

Corresponding text versions of the DTDs (without explanations) can be found
at:
http://www.topicmaps.net/simpleTMGraph3.dtd: a Topic Maps Graph, in XML
http://www.topicmaps.net/TMGraphAPI3.dtd : an API to a Topic Maps Graph, in
XML

Michel Biezunski and Steven R. Newcomb

==========================================
Michel Biezunski, InfoLoom
Tel +33 1 44 59 84 29 Cell +33 6 03 99 25 29
Email: mb@infoloom.com  Web: www.infoloom.com
==========================================
Steven R. Newcomb, Consultant
srn@coolheads.com

voice: +1 972 359 8160
fax:   +1 972 359 0270

1527 Northaven Drive
Allen, Texas 75002-1648 USA
==========================================

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