[topicmapmail] Understanding the Reference Model

[Jan Algermissen]

Alexander Johannesen wrote:

> Jan wrote:
> > I don't really understand what you mean by 'pattern',

> > The goal of the RM is to provide a standardized
> > means to define Topic Map Applications. A Topic Map Application (TMA) is
> > a set of semantics consisting of the definitions of properties and
> > assertion types, and merging rules. An example for this is the Standard
> > Application Model (SAM) that somehow reflects what people commonly seem
> > to understand "Topic Maps" to be.
> 
> Ok, so I'm a bit confused on this part; what are the differences
> between TMM and the SAM? Could the SAM be explained through TMM?

Ah yes,.....let me try to explain:

The goal of the TMM is to provide a standardized basis for defining
Topic Maps Applications. From the TMM point of view the SAM is the
Standard Application, meaning the set of properties,assertion types
and merging rules that together make up what people commonly understand
Topic Maps to be. From the TMM point of view, the SAM is not equivalent
to Topic Maps but just one Application (a very important one, that's
for sure).

Unfortunately, there is some disagreement within the ISO working group
about this as there is also the understanding that Topic Maps are
in fact equivalent to the SAM. The term SAM itself is therefore a bit
ambigous: while the TMM understands it to refer to the Standard Topic
Map Application, others understand it to refer to the ISO document
at http://www.isotopicmaps.org/sam/sam-model/ .

This document is in some sense a TMA definition of the SAM (in TMM sense),
but also goes beyond this by defining a structural abstraction for Topic
Maps.

In short:

- yes, the SAM (in the sense of the document) can be expressed in terms of
  the TMM. That is after all the purpose of the TMM.

- The TMM and the SAM (the document) both define sconcurrent tructural
  abstractions for Topic Maps. From the TMM POV a structural abstraction
  is not part of a TMA definition, as the TMM already defines one.

How these issues will be resolved remains to be seen. However, I hope
this is helping you a bit.



> > I think you would profit from playing around with it in your course
> > of getting your head into 'RM mode'. Let me know if you want the latest
> > version.
> 
> Sure do, although I'm no Python expert (assuming it's in Python?).

It's written in C and used to have a Python wrapper. Since Python's
extension API was to unstable for me to handle between 1.x and 2.3
I deferred that part and now there is a Perl wrapper available on CPAN.
But for sure, Python will be back in there....

> ...
> 
> >> I'll confine myself to this as a start-off.
> >
> > What do you mean? Doing examples? That would be great. What do you
> > have in mind?
> 
> At this stage I'm trying to grasp the TMM first, but I'm working with
> various sets of TM applications, so a way to describe these would be
> a good start and an excelent practice for me to learn it. 

Hmm....are you thinking Topic Map Application == software application?
If so, that's wrong. A TMA has nothing to do with software, it is a
set of semantics (we used the capital 'A' for the destinction).

You might want to look at

http://www.isotopicmaps.org/tmmm/TMSM-1.3/TMSM-1.3.html

This document includes an informal/experimental definition of
the Standard Application (from the TMM POV).


Jan


> I'll give
> it some thoughts.
> 
> > Thanks for trying to understand the RM. I *know* it takes some effort
> > and patience! But the concept is really very simple.
> 
> As always. :)
> 
> Alexander
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-- 
Jan Algermissen                           http://www.topicmapping.com
Consultant & Programmer	                  http://www.gooseworks.org