[topicmapmail] Expressive capabilities of Topic Maps

[jalgermissen@topicmapping.com]

Lars Marius Garshol <larsga@garshol.priv.no> schrieb am 10.09.2003,
10:01:54:
>
> * Lars Marius Garshol
> |
> |  a) Topic maps never had a notion of "simple properties", so what did
> |     you expect?
>
> * jalgermissen@topicmapping.com
> |
> | Seriously, I think it would be an enourmous limitation if Topic Maps
> | could not store, say something simple as the age of persons in a
> | simple way (as simple as with the entity relationship model).
>
> I think internal occurrences are as simple as anything is likely to be
> within topic maps. What is it you think is too complicated about them?
> Are they difficult to use?
 
No, of course they are not difficult to use. My point is that they add
substantial overhead that is not neccessary when one is only interested
in creating a simple property. I can't understand how we want to do
information management on serious data sizes and not give topic maps the
ability to represent simple properties with as little overhead as
possible. Again, if I have millions of, for example, persons with
their ages I see absolutely no reason to require topic map users to
create an object for each person<->age relationship, give that object
a scope, a type etc..
 
Consider an owner of data sets of substantial size, that are just
perfectly suited for modeling them on the basis of the entity-
relationship model, except that the data owner would like to
take advantage of the merging capability of topic maps (1).
Maybe the owner needs to plan for future integration of his data
base with those of partners. Maybe the data to be modeled consists
90% of simple properties (persons with age,street,zipcode,department;
goods with weights, prices, amount in stock) (2). Requireing to
use occurrences for all these properties does not make Topic
Maps look like a good choice (allthogh their capabilities are
explicitly demanded).
 
Why are you not concerned about this?
 
>
> | Also, just because XTM has no facility for properties does not mean
> | that Topic Maps are unable to provide one.
>
> In my mind internal occurrences are the facility provided by XTM and
> topic maps for properties, and I'm not convinced that we need another.
>
> | The Reference Model support simple properties, so why not use them?
>
> Indeed. If you want to use them, feel free.
 
It's not about what *I* need, but that I am concerned about the
usefullness of topic maps for data modeling, well, beyond XTM.
 
>
> * Lars Marius Garshol
> |
> |  b) The data model draft says what the structure of a topic map is,
> |     but *not* how to store it, so what the overhead of an occurrence
> |     is depends on the implementation.
>
> * jalgermissen@topicmapping.com
> |
> | I disagree. The current SAM draft recognises the is-ness of the
> | relationship between a topic and the information 'that is relevant
> | to the topic'. For simple properties I don't need that.
>
> I agree you may not need to support reification of simple properties,
> but what is the problem with the data model supporting that capability?
> I don't see that it necessarily adds substantial overhead in any way.
 
Hmmm, assuming maybe 20 bytes for a simple property value, I'd consider
the size of an occurrence item substantial (3).
 
 
Jan
 
(1) and propably also of the possibility that topic maps allow
    the coexistence of different views on the data.
 
(2) Thinking about this, I feel that most domains are likely to
    consist of simple properties to a high percentage (IMHO)
 
(3) Definition of occurrence item in the latest SAM draft:
    http://www.isotopicmaps.org/sam/sam-model/#sect-occurrence
 
 
 
 
 
>
> --
> Lars Marius Garshol, Ontopian
> GSM: +47 98 21 55 50
>
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Jan Algermissen                <algermissen@acm.org>
Consultant & Programmer

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