John Sowa wrote: (01)
> As another example, assume "Mary has less than 5 children, including a girl
> named Sue, and a pair of twins, one of whom is named Bill."
> In CGs, that would be
>
> [Person: Mary]->(HasChild)->[Person: {Sue, Bill, *x, *}@<5]
> [Girl: Sue] [Person: Bill]->(HasTwin)->[Person: ?x]
>
> In the pure graphic notation, coreference links could be drawn as dotted
> lines. Or they could be left as labels like *x, if the diagram is complex and
> crowded.
>
> How would you express that in OWL? (02)
First, note that the above example uses two Classes: Person and Girl, and two
objectProperties: HasChild and HasTwin. In OWL, one would declare:
- Girl to be subclassOf Person (which John omits),
and perhaps
- the domain and range of HasChild and HasTwin to be restricted to Persons, and
- hasTwin to have maximum cardinality 1 and be symmetric (none of which John
mentions).
Then we would declare
- Mary is an instance of Person,
- Mary is an instance of the class of things whose participation in the
HasChild property has cardinality less than 5.
- Sue is an instance of Girl
- Bill is an instance of Person
- Bill is an instance of the class of things who have some value for hasTwin
- Mary hasChild Sue
- Mary hasChild Bill. (03)
Now, how each of these 7 axioms is expressed depends on which OWL notation you
choose. VOWL is yet-another-OWL-notation. And yes, the representation of the
class expressions (things who ...) is a bit cryptic in all of them, but no more
so than the cryptic CG stuff that John cites. (And OBTW, writing the
cardinality constraint for Mary's children is a lot easier in OWL than in a FOL
language like KIF.) (04)
For the purpose of reasoning, it is useful to sort out the information into the
simplest axioms. One can roll up some of these declarations in OWL as well,
but it isn't clearer, and it doesn't help the reasoning process. (05)
-Ed (06)
P.S. The most readable OWL notation is Turtle, but I'm not used to writing
Turtle. (07)
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