COMEX: A Commodities Support System

1977) for representing knowledge. About twenty types of event are represented, together with crop-states, weather, commodities, quantities and prices. Frame structures are Interwoven with procedures. COMEX-0 builds frame structures by means of a formal dialogue with a user: Each frame has procedures for requesting information to instantiate its slots. Procedures attached to slots check that responses satisfy the requirements of the slot. Unsatisfied requirements complain giving a reason for unacceptability. Representing evants. event representations in two ways, INSTANTIATION of an event and AGGREGATION of several events. procedures, as well as assertions, are inherited. Aggregation is exemplified by EXCHANGING which has two parts, both of them TRANSFERINGS, which occur at the same time. When we instantiate EXCHANGING, mapping commands use definitions to construct the subcomponents so as to represent that ACT0R1 transfered 0BJECT1 to ACT0R2 and ACT0R2 transfered 0BJECT2 to ACTOR 1. This mapping makes inferences, since assertions about TRANSFERING have become available through expanding the definition of EXCHANGING. Mappings take account of constraints among slots of the sub-components. They are like Merlin mappings (Moore and Newell, 1973) but are used differently. Parts of a defined structure which use different frames but contain common elements are mapped into each other.