Re: [xtm-wg] Dynamic Generation and Serving of Topic Maps

["Steven R. Newcomb" <srn@coolheads.com>]

> From: "Graham Moore" <gdm@stepuk.com>
> Date: Fri, 3 Nov 2000 14:39:14 -0000
> I agree strongly with Lars here.
> The model that gets built from processing (importing and
> holding a representation) a topic map is not a DOM.

I, too, would like to underline, emphasize, and shout from
the housetops that:

  In their useful form, topic maps are ALWAYS topic map
  graphs.  They are NEVER topic map documents.  

    (A topic map graph is a set of nodes that represent
    topics, with interconnections between them, that fully
    expresses a topic map, and to which a random-access API
    can be provided.  A topic map graph can be implemented
    in many ways, e.g. as a relational database, as a set of
    C++ objects in memory, etc.)

  Let me say this again in a different way.  

  Topic map documents, including XML documents that conform
  to the XTM Specification, are utterly unreliable tools for
  every purpose except interchanging and reconstituting
  topic map graphs.  Topic map graphs must be created from
  topic map documents before the information contained in
  the topic map documents can be made available for any
  useful purpose.

  Let me say this again in a different way.  

  Anyone who thinks that they can use the DOM to gain direct
  access to the information contained in topic map documents
  is totally in the dark about the nature of topic maps and
  about the meaning of the information contained in topic
  map documents.  BEWARE OF THIS GRAVE ERROR.  It is based
  on a false assumption that is pervasive in Web-land, and
  this is the reason why the error is so very common.  The
  false assumption is that the syntax of an XML document is
  also always the API to the information that it contains.
  While that assumption may work for comparatively simple
  kinds of information, it cannot work for n-dimensional
  information.  Topics are inherently n-dimensional.  The
  connections between topics are inherently n-dimensional.
  The conections between the connections between the topics
  are inherently n-dimensional.  Etc.  Any interchange
  syntax for topic maps necessarily squashes all these
  dimensions into a single string.  There is not now, nor
  can there ever be, any practical way for topic map
  information, which is inherently multidimensional, to be
  represented as a single string of characters in such a way
  as to allow applications to skip the step of
  reconstituting the topic map graph and still understand
  the information contained in the topic map document.

  Objection: So, how can we get topic maps onto the web if
             they have to be interchanged and then wholly
             processed by their recipients before they can
             be used?  That idea won't scale!

  Answer: XTM 1.0 won't answer this very good question.  XTM
          1.0 will provide a syntax for the interchange of
          topic map graphs, it will describe what a topic
          map graph is, and it will describe the process by
          which an interchangeable XML topic map can be
          reconstituted as a topic map graph.

          After XTM 1.0 is published, our next task is to
          describe how to support interactions with
          remotely-maintained topic map graphs via the Web.
          Please be patient.  We're moving as fast as we
          can.  Your question about how topic maps can be
          scaled up and accessed remotely will be answered.
          Just be informed that the remote access to topic
          map graphs cannot be via the DOM.  The DOM
          provides access to the properties of parsed XML
          documents, but not to the properties of topic map
          graphs.

-Steve

--
Steven R. Newcomb, Consultant
srn@coolheads.com

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

405 Flagler Court
Allen, Texas 75013-2821 USA

****************************************************************************

> From: "Graham Moore" <gdm@stepuk.com>
> Date: Fri, 3 Nov 2000 14:39:14 -0000

> I agree strongly with Lars here.

> The model that gets built from processing (importing and holding a
> representation) a topic map is not a DOM.

> In order for XPath to perform useful topic map queries on the topic
> map serialisation means that the XPath will have to do alot of
> hopping around in order to first build the topic map model. I dont
> think that this will be pretty.


> > On Behalf Of Lars Marius Garshol
> > Sent: 03 November 2000 11:56
> > Subject: Re: [xtm-wg] Dynamic Generation and Serving of Topic Maps

> > * Dave Pawson
> > |
> > | Whats missing from XSLT/XPATH for queries, which produce XML
> > | results?

> > * Murray Altheim
> > |
> > | Yes, this was my feeling as well. If XPath and XPointer don't fill
> > | the bill, then we're in trouble. I'd think "XTMQL" would be simply a
> > | document showing how to perform common XTM queries using XPath and
> > | XPointer.

> > Topic maps and XML have two completely different and unrelated data
> > models. Using XPath for topic map queries is going to be terribly
> > awkward and not likely to provide the right kinds of functionality at
> > all.

> > Furthermore, XPath does not support updates or deletions, which TMQL
> > probably should.

> > | There shouldn't be much need for anything else. If we're talking
> > | about query languages for databases, we're no longer talking about
> > | querying topic maps as XML documents, which to me seems waaay out of
> > | scope for this activity.

> > To me it is very difficult to understand how anyone can say this.
> > Some topic maps may be XML documents, but that is an entirely
> > coincidental and not very interesting fact. I very much doubt that
> > any serious topic map applications will be based on topic maps as XML
> > documents, but rather on databases.

> > Furthermore, to TMQL, the actual form in which the topic map happens
> > to be stored should not matter at all. To be honest I'm worried to see
> > anyone at all thinking differently.
> >
> > --Lars M.

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