ON PERIODICITY IN TEMPORAL DATABASES

The issue of periodicity is generally understood to be a desirable pro perty of temporal data that should. be supported by temporal database models and their query languages. Nevertheless, here has so far not be en any systematic examination of how to incorporate this concept into a temporal DBMS in this paper we describe two concepts of periodicity, which we call strong periodicity and near periodicity, and discuss ho w they capture formally two of the intuitive meanings of this term. We formally compare the expressive power of these two concepts, relate t hem to existing temporal query languages, and show how they can be inc orporated into temporal relational database query languages,such as th e proposed temporal extension to SQL, in a clean and straightforward m anner.