[topicmapmail] Two Models of Facets

[Murray Altheim]

Murray Altheim wrote:
[...]
> For purposes of discussion I'll delineate two kinds of Topics, class
> Topics and instance Topics. And we'll call (for purposes of discussion)
> "properties" the things attached to instance Topics, and  "facets" as
> the things assigned to class Topics (we'll see if this pans out; if
> not I'll drop it). I'll also try to remember to capitalize "topic" when
> I mean Topic Map Topics. I'll use "characteristic" when I am being
> deliberately ambiguous about whether something is a facet or a property.
> 
> Now, one aspect of this I don't like necessarily is the implied rule
> that one wouldn't assign a facet to an instance, or a property to a
> class. But I am meaning to say that there are things that are
> characteristics of all members of a class, and there are characteristics
> that are meant to be assigned to a single individual. Now, without going
> too far down the extensional/intensional waterslide, I'll use an
> example.  [...]

One thing which I failed to highlight is that there aren't in either model
any special Topics used for properties or facets - that any Topic can play
the *role* of facet in a faceting Association. The hierarchy/ies that
these Topics are part of is any "natural" hierarchy that they'd be a
part of anyway. Nothing special. The inheritance of facet or property
characteristics comes from that/those hierarchies. In the example,
"eye color" is a Topic, and it can be used to express a facet, though
the Topic used to express a characteristic for an *individual's* eye
color should *probably* be an instance Topic if we're talking about
the A/property/instance/RDF model and probably should be a class Topic
if we're talking about the T/facet/class/FC model.

Murray

......................................................................
Murray Altheim                    http://kmi.open.ac.uk/people/murray/
Knowledge Media Institute
The Open University, Milton Keynes, Bucks, MK7 6AA, UK               .

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