Associations in RDF

Hi Everyone,

I have always felt uncomfortable with the notion of predicates
being represented as properties.  To me, predicates seem to have
two types: relation (or association) and attribute.  Attributes
are suitably represented as properties (could be considered synonyms).
By forcing all predicates to be properties ... are we not shortchanging
predicates as associations? 

For example, what about independent or temporary associations that should 
not be tightly bound to a subject?  Additionally, a relation that has an 
of degree is poorly modeled via a property.  Take an example of 
friendship which could have the following degrees (and many more): 
acquaintance, recurring_acquaintance, new_friend, childhood_friend,
lifelong_friend, intimate_friend, ... etc.  If we modeled all of these as 
properties, the property list of an object would grow to be unmanageable.
Instead we need to put characteristics into the association itself.  Thus,
we model an Association as a class and we can have a simple property 
that points to a particular association subclass hierarchy.

Has anyone else experienced this?  Is this a deficiency or is it covered
in ways that I am unaware of?

If it is not covered, I would propose that there be two subclasses of 
Predicate: Property (which exists) and Relation (or association).
Thus as a separate first-class object, associations can be rapidly 
queried against and not be confused with simple properties.

I think associations are important enough to be explicitly 
called out.  In seeing the RDF mapping to UML, these are made
explicit.  I just think this is so basic that it should be in the base
RDFS spec.

What do you think?

 - Mike
Michael C. Daconta
Director, Web & Technology Services

Received on Wednesday, 17 July 2002 15:36:20 UTC