This volume brings together current work on qualitative reasoning. Previous publication has been primarily in scattered conference proceedings. The appearance of this volume reflects the maturity of qualitative reasoning as a research area, and the growing interest in problems of reasoning about physical systems.
The papers present knowledge bases for a number of very different domains, from heat flow, to transistors, to digital computation. Anyone concerned with automated reasoning about the real (physical) world should read and understand this material.
Compositionality
A common theme of all these papers is explaining how physical systems work. An important shared criterion is that the behavioral description must be compositional, that is the description of a system's behavior must be derivable from the structure of the system. The term 'structure' refers to the components of the analysis, component behaviors, and the connections between components. The term 'behavior' refers to the time course of observable changes of state of the components and the system as a whole. Each component has some associated behavior, and the behavior of the system as a whole results from the interactions of the behaviors of the components through specified connections.
Locality
A shared criterion for explanation is that effects must propogate locally, through specified connections. Explanations which follow such local propagation rules are felt to be causal. This contrasts sharply with standard physics. In that paradigm, systems are described by differential equations which provide constraints on the dynamics of system state variables. Analytic techniques determine allowable time-varying behavior of these continuous state Artificial Intelligence 24 (1984)