GCH-OSQL: a temporally-oriented object-oriented query language based on a three-valued logic

The need of managing temporal information given at different levels of granularity and indeterminacy is common to many application areas. Between them, we focus on the management of clinical data. Different time granularities are also needed in querying temporal databases. In this paper, we describe GCH-OSQL (Granular Clinical History-Object Structured Query Language), an object-oriented temporally-oriented extension of SQL. GCH-OSQL is based on an object-oriented temporal data model, named GCH-OODM. GCH-OODM allows storage of temporal information at different and mixed granularities. GCH-OSQL deals with the valid time of temporal data. The temporal extension of the SELECT statement includes the addition of the TIME-SLICE and MOVING WINDOW clauses, and the capability of referring to the temporal dimension of objects in the WHERE and SELECT clauses.