Dear John, (01)
> MW> If you don't have a common upper ontology you do need to
> > have a mapping between the upper ontologies you do have. What
> > is true that having a common upper ontology give efficiency
> > benefits as the number of ontologies you are trying to integrate
> > rises. At about 4 ontologies a common ontology (at all levels
> > that are shared) pays off.
>
> Three points:
>
> 1. Note the parenthetical expression "at all levels that are
> shared". Categories that are not shared need not be aligned. (02)
MW: It depends on what you are trying to do. Full integration would
probably allow you to do things that could not be done in any of them
individually. Partial integration allows them to interoperate which
allows you to do just what each of them can do.
>
> 2. Since Matthew is a strong advocate of 4D ontologies and many
> other ontologies use a 3D approach, I suspect that he has
> not been forcing those details to be aligned. (03)
MW: I tend to go for full integration into a 4D ontology, followed by
mapping to support interoperation between legacy information systems.
>
> 3. By "efficiency", I suspect that Matthew means that the more
> ontologies you try to align, the more troublesome details
> are removed from the upper levels and put into the more
> specialized microtheories. (04)
MW: No. I mean that the more ontologies you have to map to each other
the cheaper it becomes to do one mapping from each to an integrating
ontology (which might of course be one of them).
>
> Summary: Global agreement is possible for vague things like
> WordNet or for things like OpenCyc, in which most of the axioms
> are omitted. Interoperability on the details must always be
> specified at the level of one or more microtheories. (05)
MW: This strikes me as wholly unremarkable, and essentially only
saying that lower level ontologies are more detailed than upper
level ones. Where is the surprise in that? (06)
MW: I don't think this is a good argument for or against anything
except putting axioms at the appropriate level. Upper ontologies
are more general, and so will have more general axioms. Lower level
ontologies are more specific and so will have more specific
and detailed axioms. Shock horror. (07)
Regards (08)
Matthew (09)
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