An implementation of a temporal relational database management system

111 this work, the implementation of a temporal database management system is reported. This system has been implemented on top of an existing database system that manipulates relations with set-valued attributes. The temporal relational model together with the tem])oral algebra are descril)ed. The basic set of opercitions of the extended relational algebra have been modified to handle temporal attributes. New operations have been added to help in the extraction of information from historical relations. These operations convcirt one attrilnite type to another and do selection over the time'dimension. Moreover, a statistical interface has been added to the system. This interface includes aggregate functions and a new operation, enumeration^ which derives a table of uniform data for a set of time points or intervals, from a three dimensional historical relation. A performance evaluation of the system is carried out by executing sample queries against different types of databases: snapshot, snapshot/nested and historical.