On May 18, 2007, at 3:40 AM, Phillip Lord wrote:
"MK" == Marijke Keet <[EMAIL PROTECTED]> writes:
MK> Regarding “reification design patterns” and the reification &
MK> OWL (not the thorny logic-based representation of beliefs et
MK> al), permit me to mention that support for n-ary relations
MK> ---where n may also be >2--- in description logics is already
MK> possible with DLR [1] and implemented with reasoner-support in
MK> the iCOM tool (the tool may not live up to end-user-level
MK> expectations on userfriendliness, but it works) [2].
Out of curiosity, can you describe how different or similar this is to
the result that you can achieve in the N-ary relation design pattern
for OWL?
Obviously, building things into the DL is nice, but it's not currently
representable in OWL, so would require tooling support, while the OWL
N-ary relation pattern doesn't.
I'm afraid I'm unclear how to state the OWL n-ary relation pattern
(http://www.w3.org/TR/swbp-n-aryRelations) where I really need it. In
all the examples given, the "lifted"[*] n-ary relation was never
truly a relation in the first place and always better modeled as a
class. It's kind of cheating. What if my n-ary relation is transitive
or if the 3rd argument is a temporal interval over which the relation
holds?
I think the former is doable with property role chains. Updating the
n-ary relations note with this - and all the other omitted details,
such as how to re-represent domain/range, functional properties, n-
ary relations in restrictions etc - would take a lot of work and
would make it utterly terrifying to the naive user.
Nevertheless the results are clunky and will need special tool support
[**] to avoid going insane. In general I am wary of design pattern
type things - they are usually a sign that the language lacks the
constructs required to express things unambiguously and concisely. It
sounds like DLR could provide this, which would be great.
Cheers
Chris
[*] Can someone tell me the correct terminology here? I know there
are people who hold steadfastly to "reification" insisting it's use
precedes the RDF usage.
[**] http://composing-the-semantic-web.blogspot.com/
2006_07_01_archive.html -- but not much use yet for those of us who
only use open source tools. Note the use of the R term in the non-RDF
sense...
Phil
