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|Title: ||EXPERIMENTS WITH AN INTEGER PROGRAMMING FORMULATION OF AN EXPERT SYSTEM|
|Authors: ||Dhar, Vasant|
|Issue Date: ||Mar-1989|
|Publisher: ||Stern School of Business, New York University|
|Series/Report no.: ||IS-89-039|
|Abstract: ||We present expert system (ES) and Integer Programming (IP) formulations of an NP-complete
constraint satisfaction problem (CSP). The problem involves generating a
plan for assigning faculty to courses given a variety of constraints and preferences and
other tentative data. The expert system consists of a heuristic rule-based problem
solver and a truth maintenance system. The IP model consists of about 700 zero-one
decision variables and 300 constraints. We describe and contrast the expert system
and IP models in terms of behavior, quality of results, and computational performance.
We find that the expressiveness of the IP model is hampered by its single objective
function, inability to encode various types of complex preferences, the lack of useful
output when it fails to find a feasible solution, and a general lack of control over inference.
It is also difficult to make incremental revisions to the plan produced by the IP
model. In contrast, the truth maintenance system maintains justifications for assignments,
which makes it possible to reason about incremental modifications to a plan.
In terms of performance, we found that whenever the IP approach finds a solution, it
does so quickly using the Pivot and Complement heuristic of Balas and Martin (1980).
The branch and bound always failed to find a feasible integer solution when the heuristic
failed to find one.|
|Appears in Collections:||IOMS: Information Systems Working Papers|
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