 
Summary: Journal of Arti cial Intelligence Research 8 (1998) 39{65 Submitted 6/97; published 3/98
Tractability of Theory Patching
Shlomo ArgamonEngelson argamon@cs.biu.ac.il
Moshe Koppel koppel@cs.biu.ac.il
Department of Mathematics and Computer Science
BarIlan University
52900 Ramat Gan, Israel
Abstract
In this paper we consider the problem of theory patching, in which we are given a domain
theory, some of whose components are indicated to be possibly awed, and a set of labeled
training examples for the domain concept. The theory patching problem is to revise only
the indicated components of the theory, such that the resulting theory correctly classi es
all the training examples. Theory patching is thus a type of theory revision in which
revisions are made to individual components of the theory. Our concern in this paper
is to determine for which classes of logical domain theories the theory patching problem
is tractable. We consider both propositional and rstorder domain theories, and show
that the theory patching problem is equivalent to that of determining what information
contained in a theory is stable regardless of what revisions might be performed to the theory.
We show that determining stability is tractable if the input theory satis es two conditions:
that revisions to each theory component have monotonic e ects on the classi cation of
