Valid-Time Indeterminacy in Temporal Relational Databases: Semantics and Representations

Valid-time indeterminacy is "don't know when" indeterminacy, coping with cases in which one does not exactly know when a fact holds in the modeled reality. In this paper, we first propose a reference representation (data model and algebra) in which all possible temporal scenarios induced by valid-time indeterminacy can be extensionally modeled. We then specify a family of 16 more compact representational data models. We demonstrate their correctness with respect to the reference representation and analyze several properties, including their data expressiveness. Then, we compare these compact models along several relevant dimensions. Finally, we also extend the reference representation and a representative of compact representations to cope with probabilities.

1 Introduction

Time is pervasive and in many situations the dynamics over time is one of the most relevant aspects to be captured by a data model. Many representations for temporal databases (TDBs) have been developed over the last two decades.