On Mar 25, 2009, at 2:55 PM, Bijan Parsia wrote:
On 25 Mar 2009, at 18:41, Matthias Samwald wrote:
Another predicate is needed that is less "rigourous" -
owl:kindOfLike :-)
What do we gain from non-rigorous statements?
"rigorous" is not the right term. "Less strong" is the point
Bijan,
Was the possibility of introducing an owl:kindOfLike - like
property discussed in the OWL2 working group?
No.
If yes, what came out of it? If not, why not?
There was no proposal, no user base, and no implementations.
OWL 2 came out of OWLED. At the first OWLED, the organizers
(including myself) tried to get people to figure out what they
needed and what could be done and do as much as we could that was
needed.
For years, whenever I diss the mapping use of sameAs I try to get
people to discuss alternatives. It usually goes badly at that point :)
Same here.
One obviously difficulty is that we Just Don't Know what's needed.
There's no real traditional semantics we can just borrow (the way we
do for most features in OWL; the way we used logical equality for
sameAs).
Here's a simple issue: Should we have owl:kindOfLike only? How about
owl:almostCertainlyLikeInMostCircumstances?
What behavior do you want from these? If it's always ad hoc (i.e.,
you are willing to write a program) then just coin some annotation
properties.
It's notoriously difficult for users to just come up with a feature.
Generally, when I'm discussing extensions, I have to propose various
things and spend a lot of time explaining the trade offs to get to a
reasonable starting point.
If HCLSIG, or some member, is interested in exploring better
options, I would be happy to contribute my technical expertise and
community connections.
But I can't just pull something useful out of my ass and expect it
to come out all rainbows and violets. Believe me, I've *tried*. ;)
As have several of us. A lot of people with many varied backgrounds
all agree that this needs to be done, but there doesnt seem to be any
clear consensus on what it is that needs doing
My first question for suggestions like this ("kindofLIke") is, what
properties would you expect it to have? First obvious questions:
is it
(1) symmetrical (A KOL B => B KOL A) ? If not, can you give an
example to show why not?
(2) transitive (A KOL B & B KOL C => A KOL C) ? Bear in mind that this
can give rise to arbitrarily long chains of A KOL B KOL C KOL ... Z,
and then A has to KOL Z. If not, can you give examples showing why
not? If its sometimes transitive and sometimes not, can you
characterize the differences between the cases?
(3) can any thing be KOL something, or does it only apply to some
special kind of thingie (names, identities, whatever.) ? If so, can
you say why it is restricted like this? (owl:sameAs is just good old
mathematical/logical equals, which can be applied to absolutely
anything, including classes and properties.)
(4) if A has some property or is in some class, and A KOL B, can one
infer anything at all about the properties or class memberships of B?
What?
In my experience so far, this is enough to reduce the discussion to
incoherence, because no two people will agree on the answers to just
these questions. But if KOL hasn't even got enough coherence to make
questions like this answerable, then its not really worth trying to
define it in any ontology language. Just make up some OWL property and
use it, and give it no axioms. Or use rdf: seeAlso, which was put in
the language pretty much for this reason, to be a blank carry-all for
a loose association with no formal properties.
Pat
Cheers,
Bijan.
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