## Abstract

The prevailing approach to modeling the time dimension in databases is, in one form or another, the use of an explicit representation of time. In this paper we propose a temporal relational model and algebra, based on temporal semantics, to incorporate an implicit time dimension in databases. In temporal semantics, time-varying relations are an indexed collection of ordinary relations, one for each moment in time. A temporal database is modeled by a collection of time-varying relations. Temporal databases are queried using a temporal relational algebra (TRA) which extends the relational algebra point-wise upon the set of natural numbers. Although TRA lacks the ability to explicitly manipulate time, we show how temporal aggregation and when-type queries can be formulated using a technique called "tagging". The formal properties of TRA, which can be used for query optimization, are also outlined We also compare our work with other proposed temporal algebras.

Original language | English |
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Pages (from-to) | 231-260 |

Number of pages | 30 |

Journal | Theoretical Informatics and Applications |

Volume | 30 |

Issue number | 3 |

Publication status | Published - 1996 |

## Keywords

- Formal Semantics
- Temporal Aggregation, Algebraic Properties of Operators
- Temporal Algebras
- Temporal Databases
- Temporal Logic
- Temporal Queries