Re: Concept Scheme Versioning

Hi Andy,

These are very valid concerns.

This issue seems to apply to any ontology etc. expressed in RDF/OWL,
it's a versioning problem. So I'm not very confident we can solve this
for the whole RDF world, but maybe some solutions can be proposed.

> (1) Lets say that in the 2003 version of the thesauri you define a concept with a certain scope, but latter in the 2005 version you restrict the scope.  When RDF merges the concepts from the 2003 and 2005 document instances, you will have conflicting scope notes.  What happens when someone in 2003 assigns this concept to a resource and someone else processes it in 2005 against the 2005 version?  Since the scope changed, but the URI is the same in the 2003 and 2005 versions how does the person processing it against the 2005 version know whether the resource is in scope or out of scope?

OK, this means we have to have a different URI for the newer concept. 

> (2) Lets say that in the 2005 version of the thesauri you define a concept with a certain scope, but latter in the 2005 version the concept is removed.  When RDF merges the concepts from the 2003 and 2005 document instances, you *may* have conflicting properties depending upon how you indicated the removal of the concept in the 2005 version.

So let's say we have concept A and concept B and an intermediate
concept X. There are NT/BT relations between A and X, and between X
and B. Now the new version does not have X, so it only has NT/BT
between A and B. When the triples are merged (assuming A and B have
the same URIs in both versions) then we end up with NT/BT between the
pairs:

- A,X
- X,B
- A,B

 From a semantic point of view this is not a problem as BT/NT is
transitive anyway. But this probably misses the point? Also, when
software interpreting the schema interprets BT/NT as "direct" only,
you get into problems.

> (3) Lets say that in the 2003 version of the thesauri you define a concept with a certain scope, but latter in the 2005 version you change the hierarchal relationships.  When RDF merges the concepts from the 2003 and 2005 document instances, you have a mixture of scope notes and relationship properties, e.g., NT, BT, RT, etc.  How do you know what the true definition of the concept is?

This is the same as point one (skopenote and BT/NT/RT are all
properties), so the solution can also be the same: if anything changes
in the concept we need a new URI.

> It seems to me that you really want each concept, in each expression (version) of the thesauri, to have a version specific URI.  Granted there will be common concepts between expressions of a thesauri that are defined with the same scope and relationships, but there should be some mechanism, possible OWL, to indicate which ones are the same or different and exactly how they are different.

Giving each concept a version-specific URI would certainly solve the
problem partly. Unfortunately OWL doesn't help much in solving the
remaining issue of indicating similarity. The owl:sameAs construct
means that the two URIs are two names for the same thing and the nodes
are merged, effectively creating the property clash we want to avoid.
The owl:differentFrom construct can be used to state that two things
are different, but it stops at that. We can't say _what_ is different.

Maybe a property from another vocabulary (e.g. DCMI or SKOSMAP) might
be used?

Cheers,
Mark.
(who is now going to enjoy the newest version of the concept 'weekend'
in sunny Amsterdam ;-)

-- 
  Mark F.J. van Assem - Vrije Universiteit Amsterdam
        mark@cs.vu.nl - http://www.cs.vu.nl/~mark


-- 
  Mark F.J. van Assem - Vrije Universiteit Amsterdam
        mark@cs.vu.nl - http://www.cs.vu.nl/~mark

Received on Monday, 18 July 2005 11:21:58 UTC