Roger, this was not targeted directly at TDM. I was mainly exploring OWL and definitely not suggesting multiple inheritance!
But in regards to TDM I was thinking about the consequences of allowing any defined term as a "controlled" value for InfoItems.hasValue. Is this desired? Having individual classes for the InfoItem categories now would allow us to define a specific controlled vocabulary for each category - or None if we dont think this is a good idea. These vocabularies, like CyclicityTerm, can easily be extended by anyone who really needs to. And all InfoItems are allowed to contain uncontrolled values via the hasContent property in any case. -- Markus
On 11.05.2007, at 11:30, Roger Hyam wrote:
Hi Markus,
Sounds like interesting and complex stuff and exactly what I am trying to avoid ;)
If this is for exchange standards we want to keep things as simple as possible. We also need our ontology to entail as little as possible so people can understand it and (if they are up on the technology) import it into their own business ontologies.
The role of the exchange ontology is to denote the meaning of simple fields it is not to enable connotations but to avoid them.
This is why I was sticking to simple properties with domains and ranges. Really just one up from RDFS. If it is important for a consumer to assert a hierarchy of properties then they can do that in their own ontology and import it. Who is to say that all consumers will have the same notion of that hierarchy and what is the business case for trying to impose one at this point?
If there were polymorphism of properties (overriding them in sub classes) then it would get confusing because of the multiple inheritance. I am not sure what would happen to meaning with the diamond problem - where the same property is inherited via several routes but has it's meaning changed differently on each route. It is always possible to subclass the property though and it may be possible to forbid the use of the parent property in a class - perhaps - but this is getting beyond my reading level.
Not sure if this helps,
All the best,
Roger
On 11 May 2007, at 09:54, Markus Döring wrote:
Roger, is it possible with OWL to have polymorph class properties? As properties are global and only bound to classes via range/ domain it doesnt seem to be possible to me, but maybe Im wrong. Can I redefine a propertys range depending upon the class it belongs to, so its domain? Well, that would mean to declare the same property twice with different domains and ranges. Probably impossible. It is different from classic OO thinking... -- Markus