Dear Simon,
Yes I agree.
I think in general, "role" can be 4 kinds of things, (or even more):
1) A permanent property of a person = E55 Type.
2) An office with distinct identity and unity from the individual
fulfilling the role = E74 Group
3) A incidental relationship between an Actor and an Activity = P14.1
and all the discussion here.
4) A functional specification of the default interaction between members
of a structured group,
currently in the CRM expressed via membership P107.1. One could argue,
that "membership" is a state, as such a kind of Temporal entity in its
own right. If a type of such as state is equivalent to P107.1, is
ontologically debatable.
3) and 4) and even other things boil down to the need to represent 3ary
relations. I think we should stop discussing half-hearted work-around as
if the problem would not exist.
Cheers,
Martin
On 15/10/2014 9:22 ??, Simon Spero wrote:
On Oct 15, 2014 11:45 AM, "Richard Light" <richard@
<mailto:[email protected]>light.demon.co.uk
<mailto:[email protected]>> 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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