Representing time in a support environment for the management of hospital patients

Concerns the design of a support environment to assist with the management of hospital patients in a vascular surgery department. A central component of the system is a knowledge base containing static knowledge, medical and organisational, and dynamical knowledge of patient records. The event calculus is considered as a way of reasoning about the time-dependent aspects of this knowledge. The event calculus represents change by adding the descriptions of new events (occurring at particular though not necessarily specified times) to the knowledge base which, therefore, comprises an historical record of changes in the domain model. This contrasts with an approach to updating which keeps the contents of a database in conformity with the current state of the domain model, reference to time being implicit through the time of the updates. Such databases may store temporal information and extract or impose specialised temporal relations, but cannot provide general temporal reasoning. The motivation for using a more general framework is to provide a more flexible basis for interactive retrieval and assimilation. The approach is illustrated by a description of an implementation of a simplified model of the clinical pathway in which specialists review patients at variable intervals depending on how the results of investigations and consultations are progressing