Temporal queries in OQL

Abstract

The issue of modeling and querying such temporal events has been the subject of research the database community in recent years. We present an formalism based on a new periodic temporal type called periodic element to model periodic events in temporal databases, and illustrate its suitability by extending the object-oriented query language QQL of $O_2$ with a temporal data type hierarchy with an implementation. The temporal extension to the language is achieved through a set of absolute and relative periodic types which have well-defined temporal operators/functions written in the form of methods. Periodic elements are capable of representing aperiodic, strictly-periodic, and partially-periodic absolute and relative events, and can be used for implementing calendars, scheduling and other temporal applications.