Consolidating Pipe s

Consolidation is inferring the behavioral description o f a device by composing the behavioral descriptions o f its components . The intent is to infer the behaviora l laws of the device without assuming a scenario (i .e . , initial state and external interactions) . Consolidation differs from qualitative simulation (Bobrow, 1985) i n that qualitative simulation assumes such a scenario (Bylander, 1988a) . Consolidation differs from envisioning, i .e ., the generation of all possible qualitative states and state transitions of a device, because th e result of consolidation is an intensional description . In previous work, we proposed a conceptual representation and reasoning process for performing consol idation (Bylander and Chandrasekaran, 1985) . This proposal is primarily based on predicating path s within the components with their conceptual behavior (e .g., allow, pump, move) and inferring th e conceptual behavior of path combinations . Other work has showed how qualitative differential equations (QDEs) can be composed (Dormoy and Raiman, 1988 ; Williams, 1988) . However, little work has been done to show how the conceptual level can be related to th e QDE level . The main motivation for our work is computationa l complexity. Because solving QDEs is in general computationally intractable (Davis, 1987), any theory tha t relies on QDEs without imposing sufficient restriction s on them does not explain how qualitative physics problems can be tractably solved .' As a consequence, th e practicality of such theories on specific problems can not be determined in advance of implementation . Our hope is that a conceptual analysis can provide sufficient restrictions on QDEs . So far our results are : (1) a general schema for pipe s