Prototypes and Production Rules: An Approach to Knowledge Representation for Hypothesis Formation

ACT la a computer simulation program that uses a propositional network to represent knowledge of facts and a set of productions (conditionact ion rules) to represent knowledge of procedures. There are currently four different mechanisms by which ACT can make additions andmodifications to its set of productions: designation, strengthening, generalization, and discrimination. Designation refers to the abil i ty ofproductions to call for the creation of new productions. Strengthening a production involves adjusting the amount of system reaourcea thatw i l l be allocated to its processing. Finally, generalization and discrimination refer to complementary processes that produce betterperformance by either extending or restricting the range of situations in which a production will apply. Theae learning mechanisms are uaedto simulate experiments on prototype formation. ACT successfully accounts for the effects of distance of instances from a centraltendency, frequency of individual instances, and the family resemblance structure of categories.