A comprehensive approach to 'now' in temporal relational databases: Semantics and representation

Luca Anselma, Luca Piovesan, Abdul Sattar, Bela Stantic, Paolo Terenziani

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Abstract

Now-related temporal data play an important role in many applications. Clifford et al.'s approach is a milestone to model the semantics of 'now' in temporal relational databases. Several relational representation models for now-related data have been presented; however, the semantics of such representations has not been explicitly studied. Additionally, the definition of a relational algebra to query now-related data is an open problem. We propose the first integrated approach that provides both a neat semantics for now-related data and a compact 1NF representation (data model and relational algebra) for them. Additionally, our approach also extends current approaches to consider (i) domains where it is not always possible to know when changes in the world are recorded in the database and (ii) now-related data with a bound on their persistency in the future. To do so, we explicitly model the notion of temporal indeterminacy in the future for now-related data. The properties of our approach are also analyzed both from a theoretical (semantic correctness and reducibility of the algebra) and from an experimental point of view. Experiments show that, despite the fact that our approach is a major extension to current temporal relational approaches, no significant overhead is added to deal with 'now'.

Lingua originaleInglese
Numero di articolo7506328
pagine (da-a)2538-2551
Numero di pagine14
RivistaIEEE Transactions on Knowledge and Data Engineering
Volume28
Numero di pubblicazione10
DOI
Stato di pubblicazionePubblicato - ott 2016

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