[Sigia-l] Facets vs. ontologies [was: Sigia-l] Findability - hierarchies

[lisa colvin]

Hi Travis,

Ontologies need not be a catch-all! See below ;)

> Travis said:

> At this point it could even be argued that such a
> faceted scheme is MORE 
> strongly typed than an ontology. The ontology is
> kind of a catch-all for 
> every type of relationship. FC, on the other hand,
> forces you to specify 
> which end of the relationship is the descriptor, and
> which is the 
> descriptee, like in this example.

Topicmaps, faceted classfication...all define
ontological structures.  An ontology is:

1. A set of entities/concepts/classes/individuals...
2. Relationships between those entities/co/cl/in...

Depending on the ontology language used, one can
define a set of typed relationships (restricting the
argument types to each relationship). The most common
relationships are those of subClass and class
membership (instance of). 

All the ontology systems I've worked with have enabled
the user to define new relationships. Part of defining
a new relationship is in constraining the argument
types for that relationship.  Expert systems which use
ontologies *must* have a heavily-typed ontology in
order to have proper truth-maintenance and constraint
satisfaction. 

That said, ontologies built for the purpose of
browsing and not for use with an expert system, need
not be heavily-typed.

;)lis 





__________________________________________________
Do you Yahoo!?
Yahoo! Mail Plus - Powerful. Affordable. Sign up now.
http://mailplus.yahoo.com