Temporal coalescing is a unary operator applicable to temporal databases that is similar to duplicate elimination in conventional databases. Temporal coalescing merges value-equivalent tuples, i.e., tuples with overlapping or adjacent timestamps and matching explicit attribute values. Tuples in a temporal relation that agree on the explicit attribute values and that have adjacent or overlapping timestamps are candidates for temporal coalescing. The result of operators may change if a relation is coalesced before applying the operator. For instance, an operator that counts the number of tuples in a relation or an operator that selects all tuples with a timestamp spanning at least 3 months are sensitive to temporal coalescing.
- 2.Böhlen MH, Snodgrass RT, Soo MD. Coalescing in temporal databases. In: Proceedings of the 22th International Conference on Very Large Data Bases; 1996. p. 180–91.Google Scholar
- 5.Leung C, Muntz R. Query processing for temporal databases. In: Proceedings of the 6th International Conference on Data Engineering; 1990. p. 200–8.Google Scholar
- 6.Leung TYC, Pirahesh H. Querying historical data in IBM DB2 C/S DBMS using recursive SQL. In: Clifford J, Tuzhilin A, editors. Recent advances in temporal databases. Berlin: Springer; 1995.Google Scholar
- 9.Sadeghi R, Samson WB, Deen SM. HQL – a historical query language. Technical report, Dundee College of Technology, Dundee, September 1987.Google Scholar
- 12.Snodgrass RT. Developing time-oriented database applications in SQL. San Mateo: Morgan Kaufmann; 2000.Google Scholar
- 13.Tansel A, Clifford J, Gadia S, Jajodia S, Segev A, Snodgrass RT. 1Temporal databases: theory, design, and implementation. Redwood City: Benjamin/Cummings; 1993.Google Scholar
- 14.Zhou X, Wang F, Zaniolo C. Efficient temporal coalescing query support in relational database systems. In: Proceedings of the 17th International Conference Database and Expert System Applications; 2006. p. 676–86.Google Scholar