Modeling Time: Back to Basics

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  • Technical report TR96-03. Most of the work in modeling time in information systems has concentrated on issues such as support for historical information and providing query facilities to manipulate such information. In doing so, some simplistic view of the underling nature of time has been assumed. However, the domain of time is far from being simplistic. In this paper, we outline the various issues which arise in modeling basic temporal entities and propose solutions to these issues. More specifically, we note that the nature of temporal information can either be anchored (e.g., October 25, 1995) or unanchored (e.g., week), and is usually available in multiple granularities (e.g., the airline flight departure and arrival times are usually given in minutes, while the history of the salary of an employee is usually recorded in days). Physical temporal information also needs to be represented in a manner so as to be human readable. This is achieved using calenders. In this work, we show how both anchored and unanchored temporal entities are represented within the context of calenders. We discuss how calenders provide relationships between multiple granularities and facilitate the conversion of anchored and unanchored times from one granularity to another. We also give the semantics of various operations on anchored and unanchored times. | TRID-ID TR96-03

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    Attribution 3.0 International