Integration of temporal reasoning and temporal-data maintenance into a reusable database mediator to answer abstract, time-oriented queries: the Tzolkin system

The ability to reason with time-oriented data is central to the practice of medicine. Monitoring clinical variables over time often provides information that drives medical decision making (e.g., clinical diagnosis and therapy planning). Because the time-oriented patient data are often stored in electronic databases, it is important to ensure that clinicians and medical decision-support applications can conveniently find answers to their clinical queries using these databases. To help clinicians and decision-support applications make medical decisions using time-oriented data, a database-management system should (1) permit the expression of abstract, time-oriented queries, (2) permit the retrieval of data that satisfy a given set of time-oriented data-selection criteria, and (3) present the retrieved data at the appropriate level of abstraction. We impose these criteria to facilitate the expression of clinical queries and to reduce the manual data processing that users must undertake to decipher the answers to their queries. We describe a system, Tzolkin, that integrates a general method for temporal-data maintenance with a general method for temporal reasoning to meet these criteria. Tzolkin allows clinicians to use SOL-like temporal queries to retrieve both raw, time-oriented data and dynamically generated summaries of those data. Tzolkin can be used as standalone system or as a module that serves other software systems. We implement Tzolkin with a temporal-database mediator approach. This approach is general, facilities software reuse, and thus decreases the cost of building new software systems that require this functionality.