[topicmapmail] Expressive capabilities of Topic Maps

[jalgermissen@topicmapping.com]

[jan]
> >
> > What if my primary key is latitute/longitude data? Represented as a
> > two-column primry key?
> >
> >
[thomas]
> I have not worked this one out yet.  That is why I limited what I said to
> atomic keys.  One way to handle it would be to create a topic whose subject
> is the lat/long combination (since it would be a primary subject of
> discourse).  

With a lat/long, perhaps it would be a "point", or a "city",

But the lat/long *is* the subject, how can that be a point or a city
at the same time?

> for example.
> 
> Generally speaking, a field that is a foreign key pointing to another table
> would be represented by an association 

Which would require that the association be 'able to' cause merges based
on the lat/long player.

(and the column label would represent
> the role), and a literal or scalar value would be represented by an
> occurrence (and the column label would represent the occurrence type).

I do not really understand what you mean, can you give an example?

> > A basename has
> > > no real equivalent, but could become simply another column (or more) in
> the
> > > table.
> >
> > Topics can have more than one basename.....
> >
> 
> That is why I said "or more", though really you would want to put the names
> into a separate table - that's just the mechanics of doing one-to-many
> relationships in a relational database.  In practice, though, many topics
> will only ever have one name.  If you know that about your data in advance,
> you can simplify the design.  

Hmmm...

For example, the topic name might be the title
> of a web page.  A web page can only have one value (ignoring possible
> changes over time, which could be handled in a simple or complicated way,
> depending on your needs).
> 
> > >
> > > This plan has the advantage that it is simple, has low overhead, and
> that
> > > the data values are literals (or references to some other resource),
> which
> > > is the case with the table cell values.  That is why I say this is an
> > > appropriate mapping.
> >
> > IMHO, it is not possible but open to be proven wrong.
> >
> 
> I don't understand the meaning of this sentence,

I meant it is impossible to achive 'the power of topic maps'
with  ER modeling.

but anything open to be
> proven wrong sounds good to me.  When it is not open to be proven wrong,
> that's when I worry.

Not to worry, I am absolutely open. I have been working on this the
last 6 months or so and I am pretty sure it is important. I try to
keep our eyes open since there are more people that think that 
Topic Maps are more than XTM or HyTM. So a discussion on this is
better than no discussion. Thanks for dedicating your time to
this thread, Thomas.

Jan

> 
> Cheers,
> 
> Tom P
> 
> 
> _______________________________________________
> topicmapmail mailing list
> topicmapmail@infoloom.com
> http://www.infoloom.com/mailman/listinfo/topicmapmail
-- 
Jan Algermissen                <algermissen@acm.org>
Consultant & Programmer

http://www.topicmapping.com
http://www.gooseworks.org