Steve,

Notice in Bob's examples that use cases are a tool for all software 
engineering tasks, whereas competency questions are used primarily in 
ontology design. A couple of advantages in expressing ontology use cases 
as competency questions are:

i. "Can the competency question be answered?"  can be easier to answer 
than "Is the use case satisfied?"

ii. Posing the competency questions as queries can give hints about the 
structure of our desired ontology.
This is somewhat ass-backwards, since the structure of the ontology 
determines the structure of the query (not vice versa), but since 
ontologies exist to be queried, thinking about the shape of queries can be 
helpful in determining the shape of the ontology.

To take an example:

Your Individual/BiologicalEntity use case 1 is "allow for linking multiple 
Occurrence records that involved the same organism at different times 
and/or places"

This can translate to

"Find all occurrences of [individual]"

or

select ?occurrence
where {
          ?occurrence rdf:type dwc:occurrence .
 	?occurrence dwc:ofIndividual [individual] .
}

We can then consider our design issues with reference to the query. For 
example: When answering this query, does it matter whether the scope of 
Individual/Biological Entity includes organelles or wolf packs? Does it 
matter if the Individual/BiologicalEntities are taxonomically homogeneous? 
To me, the clear answer to both questions is no.

Now consider your Individual/BiologicalEntity use case 3:
"To link multiple Identifications of the same individual organism, 
particularly when these Identifications were based on different pieces of 
evidence arising from the same individual"

This would, I think, give rise to a number of competency questions, 
including: "Find all identifications of [Individual]"

or

select ?identification
where {
 	?identification rdf:type dwc:Identification .
 	?identification dwc:ofIndividual [individual] .
}

Now let's consider those same design issues:
Does it matter if the scope of Individual includes organelles or wolf packs?
No.
Does it matter whether or not Individuals are taxonomically homogeneous?
Yes, for the reasons you gave, which involve the non-heritability of properties in a partonomy.

Reading the above, you might think "I've gained no new insight from the 
competency questions." But you've already put considerable thought into 
how various ontology design decisions will affect our ability to satisfy 
the use cases. In general, the competency question methodology is meant to 
focus and streamline our consideration of design questions.

Joel.

On Tue, 26 Jul 2011, Bob Morris wrote: