[topicmapmail] basics II - Inheritance in Topic Maps

[Kal Ahmed]

Hi Kathy,

There are no explicit rules in the topic map standards that either
require or enforce inheritance. The precise nature of the inheritance is
therefore left to the application (which is the right place for it
IMHO). You can use a query language such as tolog or AsTMA? to extract
"inherited" properties from a particular instance.

If you do decide to model inheritance in your application, I would
beware of the kind of inheritance model that you suggested below -
inheriting properties from a class to an instance of the class. I would
expect a class to define the constraints on instances (e.g. all "Person"
instances must have a "Name" occurrence) and only inherit properties
along subclass-superclass relations (e.g. all "Living Being" instances
must have a "Date Of Birth" occurrence, "Person" is subclass of "Living
Being" therefore all "Person" instances must have a "Date Of Birth"
occurrence). I would not expect an instance to inherit properties (such
as a relationship to another class) from its class.

You might find [1] a useful primer in ontology development. Although
this document discusses development of ontologies using the Protege
ontology editor, the principles apply equally to development of
ontologies using topic maps.

Cheers,

Kal

[1] Ontology Development 101 -
http://protege.stanford.edu/publications/ontology_development/ontology101.html

On Mon, 2003-06-02 at 16:02, Lieberknecht, Katharina wrote:
> Hello,
> thank you all for your answers on subject basics.
> Here is basics II and I would be grateful again for any help.
> 
> My question is,
> how does inheritance work with topic maps?
> 
> 
> I want to make a tm only with the general relationship "is-related-to
> (somehow)" 
> And the more specialized "superclass-subclass" (is-a) relationship.
> 
> Now I wonder whether instances of the topics inherit from their topic types?
> And if, how far backwards do they inherit?
> Are there rules for inheritance?
> 
> Example:
> 
> Science super-to physics
>     physics super-to acoustics
>     physics super-to mechanics
>     physics super-to optics
>                                                                      optical
> element is-related-to optics	
>     optical element super-to lenses
>     optical element super-to mirrors	
>                                                                      optical
> element is-related-to photographic equipment
>     photographic equipment super-to camera
>  
> my_camera is-instance of camera
> 
> 1. Is my_camera then automatically related-to optical elements, optics,
> physics and science?
> 
> Going further
> 
>  
> acoustic element is-related-to acoustic
>     acoustic element super-to amplifier
>        amplifier super-to audio amplifier
> 
> 2. Is audio amplifier or just amplifier then related to physics and then
> related to my_camera?
>     Or to be more precise, does an application infer audio amplifier to be
> related to my_camera?
> 
> 
> greetings
> Kathy