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Re: FOL versus Rule Languages - A tutorial

From: Jim Hendler <hendler@cs.umd.edu>
Date: Fri, 26 Aug 2005 08:38:57 -0400
Message-Id: <p0623096ebf34b9225fba@[]>
To: doug.foxvog@deri.org, Dieter Fensel <dieter.fensel@deri.org>
Cc: public-rule-workshop-discuss@w3.org, Christian de Sainte Marie <csma@ilog.fr>

All- I'm running out the door, not back for a few days -- but looking 
at the recent mail, Dieter's comments, etc - it seems to me there is 
a convergence on a "compromise" space occuring -- the charter as 
written could be changed in a few simple ways to, basically, allow 
the WG to work out some of the details - the compromise space may 
live somewhere around here:

1 - FOL v. model -- the charter as written, with a few small wording 
changes, woudl allow a WG to produce the following
   i - a FOL-syntax based language for exchange (Call this Rules Full) 
- this would essentially be the "XML for the rules"
  ii - a "semantic" specification for that syntax that might be less 
precise than needed for rule reasoning  (in fact, I can imagine that 
an operational or axiomatic semantics may be just fine for this) -- 
this semantics is not intended for computational use, but for clarity 
of specification
  iii - a subset of this language (or, more precisely a profile of the 
langauge - as OWL DL is a profile of OWL Full) that is intended for 
computational use - I would imagine that any of the main things 
people have argued for (datalog, Horn, Courteous LP, etc.) could be a 
possible basis for this, and the WG would need to work that out - let 
me call this Rules Comp because I can't think of anything better 
right now.
  iv. a precise semantics (with a single model as Dieter defined it) 
for this language
Note that this would be sort of like WebOnt did with OWL Full and OWL 
DL - but by knowing in advance this was a possibility, the language 
design would be much easier -- in OWL the realization that we could 
do both didn't occur until very late in the game - and if we'd 
realized going in we might have made some decisions differently that 
would have made things easier in the end.

2 - OWL and this language -- the compromise above would need to cause 
the words on OWL to change a little - the compatibility with OWL that 
Sandro specifies would work with the Rules Full language, but would 
need to be described differently with the restricted subset -- I 
think just specifying that the WG has to clearly specify the mapping 
from OWL to Rules Comp (and note, that this can be from OWL Full - 
i.e. some OWL restrictions for DL may not be needed for the rules - 
cf. nominals are easy in rules languages)

3 - NAF v. SNAF - I disagree with Dieter and some others that this is 
not an important issue - I personally think it will be the critical 
issue as to whether we end up with a rules language or a new rules 
language that is the basis for Semantic Web applications (for those 
who know what I mean, think of the difference in cwm with and without 
log:semantics and quoting) -- but that said, the charter can leave 
this vague and the WG can decide -- I would do this by removing the 
"NAF is out of scope" - but I would leave in something about the 
ability to close worlds (this needs to be rewritten a bit) -- so in 
essence I would legitimize the WG dealing with this issue, but 
wouldnt' demand a specific solution

  Anyway, if I was putting on my old WebOnt chair hat, I'd be nervous 
about how large the charter space was in the above (a narrower 
charter is easier for a chair), but happier because my hands wouldn't 
be tied and the WG could produce use cases and requirements that 
would guide all of the above...

oops - this was gonna be a short message ... sorry

Professor James Hendler			  Director
Joint Institute for Knowledge Discovery	  	  301-405-2696
UMIACS, Univ of Maryland			  301-314-9734 (Fax)
College Park, MD 20742	 		  http://www.cs.umd.edu/users/~hendler
Received on Friday, 26 August 2005 12:39:23 UTC

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