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RE: [higgins-dev] Representing Metadata in the Higgins Ontology

Paul,

I guess my problem with both metadata as well as relationships are that, while I can see the potential need (though still can't clearly articulate it) for a semantic distinction, I do not see a need for a model distinction.  In other words, to me, they are still all just attributes.  Under your suggestion, I can't make metadata something that it may make perfect sense to make it (ie. a higgins:simpleValue for attribute metadata or a higgins:attribute for a Digital Subject).  To maintain the semantic distinction, I could see creating "metadata attributes", "relationship attributes" and .... ummm, say "attribution attributes" :) ... dunno.  Anyway, I'd like specificity in the model to call out the semantic distinction, even if, underneath we all agree they are like attributes but sometimes with other things (ie. relationships), sometimes without (ie. metadata?).  I believe this would also complement the IFilter interfaces we've come up with so far.

As I said, I also believe maintaining this semantic distinction will be an additional burden on the CP implementor but if the distinction is important, I think it's worth clearly calling out in the model.  BTW, I'm still thinking hashing out the "person with relationship" example will help further this issue which, together with the filter work we're doing, are the most germane items for us at the moment.  In fact, I believe the filter interfaces could be influenced by the outcome of this so I'd like to get that example worked out.  We can add metadata as well and resolve the whole thing at once.

Shall we meet on the IRC?

Tom

>>> "Paul Trevithick" <paul@xxxxxxxxxxxxxxxxx> 10/17/2006 2:13 PM >>>
> 
> It doesn't look like we're labeling anything specifically as metadata.  We
> just define a new object property, create a class for it's range, set it's
> domain(s) and that appears to be it.  This seems to require that the
> implementor of an IdAS CP will have to have a table that says ... for
> example, "timeSpan" is metadata, not an attribute.  Is this correct?

You're right that the word "metadata" isn't explicitly used anywhere in
higgins.owl. The semantics of this word are defined by the IdAS API/CPI.

>From the RDF/OWL perspective, we could create a consistent (with IdAS)
definition of higgins:Attribute metadata as:

  any RDF property whose domain is higgins:Attribute and which is 
  neither "higgins:complexValue" nor "higgins:simpleValue".  

And we could define higgins:DigitalSubject metadata as:

  any RDF property whose domain is higgins:DigitalSubject and which
  is neither "higgins:attribute" nor "higgins:relationship"

BTW, I'd have to ask Jim if he thought we should also exclude
"higgins:uniqueIdentifier" or not.

And we could define higgins:SubjectRelationship metadata as:

  any RDF property whose domain is higgins:SubjectRelationship
  and which is neither higgins:contextURI nor higgins:subjectCUID 

> 
> I'm trying to define some metadata for a derived ontology we're working on
> and I feel like, especially for derived ontologies, we'll need to
> specificall call things out as metadata.  Of course, I may just be out in
> left field here, so let me give the specific example ... of course, this
> may just be an extension of the Relationship vs. Attribute discussion but
> hey, I'm trying to make progress where I can ...

Let me know what you think of the above. If that doesn't work for you, you
can define your own concept (RDF property) in your sub-ontology and create
sub-properties from that. And if that doesn't work, there are other
options...

> 
> I want to define an object property, as far as I can tell, as a
> subProperty of a &higgins;relationship. 

You can certainly define a sub-property of higgins:relationship, but I would
have thought that its range would be a subclass, C, of
higgins:SubjectRelationship. And I would have thought that it is instances
of C that are the places where you can hang all kinds of RDF properties
(much like our postalAddress example).

BTW, on a related note. I'm still open to changing higgins.owl such that the
higgins:SubjectRelationship is a sub-class of higgins:Attribute as we
discussed last Thursday. Doing so would, through inheritance, give
SubjectRelationship (optional) "metadata" properties such as source,
timeSpan, etc. Would that also help?

 I want my object property to have
> metadata and, as per the IdAS API, a relationship can have metadata.
> That's good.  What do I need to do in my ontology to define this metadata,
> identify it as metadata, and restrict it to the object property I desire?

Let me know what you think of what I've written above, before I try to
answer further.
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