A TEMPORAL QUERY SYSTEM FOR PROTOCOL-DIRECTED DECISION-SUPPORT

Chronus is a query system that supports temporal extensions to the Str uctured Query Language (SQL) for relational databases. Although the re lational data model can store time-stamped data and can permit simple temporal-comparison operations, it does not provide either a closed or a sufficient algebra for manipulating temporal data. In this paper, w e outline an algebra that maintains a consistent relational representa tion of temporal data and that allows the type of temporal queries nee ded for protocol-directed decision support. We also discuss how Chronu s can translate between our temporal algebra and the relational algebr a used for SQL queries. We have applied our system to the task of scre ening patients for clinical trials. Our results demonstrate that Chron us can express sufficiently all required temporal queries, and that th e search time of such queries is similar to that of standard SQL.