Jack and Mark, (01)
I've been backing up through this rather lengthy thread, and I finally
got to your two comments near the beginning: (02)
JP
> If I might add, I will assert that predicates as first class citizens
> is perhaps the only difference between an RDF graph and a topic map. (03)
MHL
> Consider the triple {CompanyX employs Person1} using a predicate called
> "employs". The triple implicitly describes what an English speaker would
> conceptualize as an "employment", with attributes such as "start date",
> "end date", a location, etc. (04)
Yes. This is an important issue, and it's obscured by an unfortunate
tendency of some logicians to call verbs predicates. (05)
Peirce observed that when you say "Mary gave a child a book" there
are four entities involved: Mary, the child, the book, and the act
of giving. He allowed any or all of the four entities to have its
own existential quantifier (or "line of identity"). (06)
About 70 years later, Donald Davidson rediscovered the advantages of
assigning quantified variables to verbs -- for the same reasons that
Jack and Mark cite. (07)
For conceptual graphs, anything you might want to refer to or link to
is represented by a concept node. Anything you don't intend to refer
to is represented by a relation node. But you always have an option
of analyzing any relation as a graph with more nodes that can be
referred to or linked to. (08)
For the KR ontology (http://www.jfsowa.com/ontology/ ), the default
mapping is to assign a concept node to every verb. That node has
an implicit quantifier, which represents the action or the state. (09)
The idea of using the letters SVO to refer to the three parts of
an RDF triple is more confusing than helpful. I don't recommend it. (010)
John (011)
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