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From: lucdr@kim.cs.kuleuven.ac.be (Luc De Raedt)
Newsgroups: comp.lang.prolog
Subject: Information requested : theta subsumption
Message-ID: <1342@n_kulcscs.kuleuven.ac.be>
Date: 10 Nov 90 01:12:21 GMT
Sender: news@cs.kuleuven.ac.be
Organization: Dept. of Computer Science (K.U.Leuven)
Lines: 27
Originator: lucdr@kim.cs.kuleuven.ac.be

Hello,

I'am looking for information concerning theta-subsumption of clauses
as defined by Plotkin in Machine Intelligence, 5 , 1970.

He states that a clause c subsumes a clause c' iff
there is a substitution t such that ct is a subset of c'.
c can also be considered as a generalization of c'.

My problem is that most  works on theta-subsumption
address either : 
	* subsumption tests
or	* finding the least genereralization of two clauses

I have a different problem:
I want to have a (computationally attractive) algorithm
to compute the following :

given : a clause c
find : all proper minimal generalizations of c 

Information concerning theoretical properties of theta subsumption of clauses
is also welcome.

Luc De Raedt
KULeuven
email :  lucdr@cs.kuleuven.ac.be