Abstract
Time representation and temporal reasoning are of crucial importance to clinical diagnosis. In this paper we present a general model for diagnostic knowledge, the Causal-Temporal-Action (C-T-A) model. This has a central tri-planar structure for the representation, in causal terms, of knowledge on disorders and physiological processes. The central structure is bounded by two other, orthogonal planes that represent temporal constraints and therapeutic actions. These planes function to constrain the existences of the temporal entities residing on the central structure. A major focus of the paper is the temporal constraints plane of the C-T-A model. An abstract structure, the Abstract Temporal Graph (ATG) is proposed for the representation of temporal constraints. Specific cases of the ATG structure encountered in the literature on temporal clinical diagnosis are discussed and algorithms for checking the consistency and satisfiability of temporal constraints are presented. These algorithms are of relevance to the validation of diagnostic knowledge and patient data and the evaluation of diagnostic hypotheses.