Definition
A temporal expression is a syntactic construct used, e.g., in a query that evaluates to a temporal value, i.e., an instant, a time period, a time interval, or a temporal element.
Key Points
Advanced by Gadia [1], a temporal expression is a convenient temporal query language construct.
First, any temporal element is considered a temporal expression. As Gadia uses a discrete and bounded time domain, any subset of the time domain is then a temporal expression. Next, an attribute value of a tuple in Gadia’s data model is a function from the time domain to some value domain. Likewise, the attribute values of a tuple are valid during some temporal element. To illustrate, consider an (ungrouped) relation with attributes Name and Position. An example tuple in this relation is:
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Recommended Reading
Gadia SK. A homogeneous relational model and query languages for temporal databases. ACM Trans Database Syst. 1988;13(4):418–48.
Jensen CS, Dyreson CE, editors. A consensus glossary of temporal database concepts – February 1998 version. In: Etzion O, Jajodia S, Sripada S, editors. Temporal databases: research and practice, Berlin: Springer; 1998. p. 367–405.
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Jensen, C.S., Snodgrass, R.T. (2018). Temporal Expression. In: Liu, L., Özsu, M.T. (eds) Encyclopedia of Database Systems. Springer, New York, NY. https://doi.org/10.1007/978-1-4614-8265-9_1420
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DOI: https://doi.org/10.1007/978-1-4614-8265-9_1420
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