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From: jacob@NRL-CSS.ARPA (Rob Jacob)
Newsgroups: comp.ai.digest
Subject: Re: Software Development and Expert Systems
Message-ID: <8801270004.AA12634@nrl-rjkj.arpa>
Date: 27 Jan 88 00:04:24 GMT
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To: sross@cs.ucl.ac.uk

Saw your message about software engineering techniques for expert
systems on the AIList.  This may not be quite what you had in mind,
but, here at the Naval Research Laboratory Judy Froscher and I have
been working on developing a software engineering method for expert
systems.  We are interested in how rule-based systems can be built so
that they will be easier to change.  Our basic solution is to divide
the set of rules up into pieces and limit the connectivity of the
pieces.

I'm going to attach a short abstract about our work to the end of this
message and some references.   Hope it's of use to you.

Good luck,
Rob Jacob

ARPA:	jacob@nrl-css.arpa
UUCP:	...!decvax!nrl-css!jacob
SNAIL:	Code 5530, Naval Research Lab, Washington, D.C. 20375


    Developing a Software Engineering Methodology for Rule-based Systems

			    Robert J.K. Jacob
			   Judith N. Froscher

			Naval Research Laboratory
			    Washington, D.C.

Current expert systems are typically difficult to change once they are
built.  The objective of this research is to develop a design
methodology that will make a knowledge-based system easier to change,
particularly by people other than its original developer.  The basic
approach for solving this problem is to divide the information in a
knowledge base and attempt to reduce the amount of information that
each single programmer must understand before he can make a change to
the expert system.  We thus divide the domain knowledge in an expert
system into groups and then attempt to limit carefully and specify
formally the flow of information between these groups, in order to
localize the effects of typical changes within the groups.

By studying the connectivity of rules and facts in several typical
rule-based expert systems, we found that they seem to have a latent
structure, which can be used to support this approach.  We have
developed a methodology based on dividing the rules into groups and
concentrating attention on those facts that carry information between
rules in different groups.  We have also developed algorithms for
grouping the rules automatically and measures for coupling and cohesion
of alternate rule groupings in a knowledge base.  In contrast to the
homogeneous way in which the facts of a rule-based system are usually
viewed, the new method distinguishes certain facts as more important
than others with regard to future modifications of the rules.

                           REFERENCES

R.J.K. Jacob and J.N. Froscher, "Facilitating Change in Rule-based
Systems," pp. 251-286 in Expert Systems: The User Interface, ed. J.A.
Hendler, Ablex Publishing Co., Norwood, N.J. (1988).

R.J.K. Jacob and J.N. Froscher, "Software Engineering for Rule-based
Systems," Proc. Fall Joint Computer Conference pp.  185-189, Dallas,
Tex. (1986).

J.N. Froscher and R.J.K. Jacob, "Designing Expert Systems for Ease of
Change," Proc. IEEE Symposium on Expert Systems in Government pp.
246-251, Washington, D.C. (1985).

R.J.K. Jacob and J.N. Froscher, "Developing a Software Engineering
Methodology for Rule-based Systems," Proc. 1985 Conference on
Intelligent Systems and Machines pp. 179-183, Oakland University
(1985).

R.J.K. Jacob and J.N. Froscher, "Developing a Software Engineering
Methodology for Knowledge-based Systems," NRL Report 9019,  Naval
Research Laboratory, Washington, D.C. (1987).