Synonyms
Time distance; Time interval
Definition
A span is a directed duration of time. A duration is an amount of time with known length, but no specific starting or ending instants. For example, the duration “1 week” is known to have a length of 7 days, but can refer to any block of seven consecutive days. A span is either positive, denoting forward motion of time, or negative, denoting backwards motion in time.
Key Points
Concerning the synonyms, the terms “time interval” is generally understood to denote an anchored span in the general community of computer science. Only in the SQL language does “time interval” denote a span. The term “span,” which has only one definition, is thus recommended over “time interval” for works not related to the SQL language. This use is unambiguous.
A “duration” is generally considered to be non-directional, i.e., always positive. The term “time distance” is precise, but is longer.
Cross-References
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Bettini C, Dyreson CE, Evans WS, Snodgrass RT, Wang XS. A glossary of time granularity concepts. In: Etzion O, Jajodia S, Sripada S, editors. Temporal databases: research and practice, LNCS 1399. Berlin: Springer; 1998. p. 406–13.
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, LNCS 1399. Berlin: Springer; 1998. p. 367–405.
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Jensen, C.S., Snodgrass, R.T. (2018). Time Span. 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_1429
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