tailieunhanh - Integration of Temporal Reasoning and Temporal-Data Maintenance into a Reusable Database Mediator to Answer Abstract, Time-Oriented Queries: The Tzolkin System

Extent of knowledge sharing: Related to the above problem is the question of how much knowledge is available to the system during its query optimization process. In particular, the first step in choosing a query evaluation strategy is likely to be identifying which nodes have materialized views that can speed query processing. A simple technique would be to use a centralized catalog of all available views and their locations, analogous to the central directory used by Napster. Yet this model introduces a single point of failure and a potential scalability bottleneck. Alternatively, one may attempt to replicate the complete catalog at all peers, but this. | Journal ofIntelligent Information Systems 13 121-145 1999 c 1999 Kluwer Academic Publishers. Manufactured in The Netherlands. Integration of Temporal Reasoning and Temporal-Data Maintenance into a Reusable Database Mediator to Answer Abstract Time-Oriented Queries The Tzolkin System JOHN H. NGUYEN jnguyen@ YUVAL SHAHAR shahar@ SAMSON W. TU tu@ AMAR K. DAS das@ MARK A. MUSEN musen@ Stanford Medicalinformatics Stanford University School of Medicine Stanford CA 94305-5479 Abstract. 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 . 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 SQL-like temporal queries to retrieve both raw time-oriented data and dynamically generated summaries of those data. Tzolkin can be used as a standalone system or as a module that serves other software systems. We