[Crm-sig] reified association vs sub-event

Simon Spero sesuncedu at gmail.com
Wed Oct 15 21:22:58 EEST 2014


On Oct 15, 2014 11:45 AM, "Richard Light" <richard@
<richard at light.demon.co.uk>light.demon.co.uk <richard at light.demon.co.uk>>
wrote:

I. Properties of properties.

> If you do this, the subproperty simply takes the place of the original
more generic property in an RDF expression of the statement, and the result
is a meaningful RDF triple.  If, instead, you try to express "property of a
property" as RDF, you find that you are trying to construct a triple with a
predicate as its object; something RDF does not allow.

This paragraph may confuse some people so I would add some clarifications.

1. It's perfectly ok to make property assertions whose subjects are
properties, in both RDF and in OWL 2. These assertions are about the
property itself, rather than any particular use of the property.

2. It is possible to make property assertions whose value is a property, in
both RDF and OWL. For example one could state that a class has subclasses
that are partitioned based on the value of the specified property.

3. In OWL 2 it is possible to add annotations to a property assertion
axiom. These annotations are only about the particular act of assertion,
rather than what is being asserted.

4. In RDF it is possible to make assertions about an RDF statement by using
the RDF reification mechanism. RDF reification is generally considered to
be pretty bad (a reified statement does not even entail the original
statement).

II. Subproperties vs. Reified associations

1. Using subproperties instead of reified entities makes it easier to use
off-the-shelf reasoners.  For example, if there are constraints that apply
to a particular role, it may require creating one or more new subclasses to
which the constraints may be applied (these can, of course, be anonymous,
but that may not make things easier to use).

Additionally there may be optimizations for retrieval of subproperties that
are not otherwise available.

2. Using reified associations labelled with concepts from a version of SKOS
supporting hierarchical relationships does not automatically entail that
hierarchy for the associations.

III.  Roles and subevents.

It is possible to treat subevents as a subclass of roles, but the typical
motivation would be if the sub-event was an event in its own right. See eg.
http://www.cyc.com/tutorials/roles-and-event-predicates

IV. Other meanings of "Role" in applied ontology.

Some schools of thought use the term Role to refer to things like a being a
Producer. Because some person may not always be or have been a Producer,
they do not consider it appropriate for that individual to be an instance
of Producer.
DOLCE and related work tend to follow this approach.

An alternative is to treat the person-as-producer as a subpart of the
person, or to treat class membership as holding in an interval.
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