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Object-Role Modeling Workbook: Data Modeling Exercises using ORM and NORMA by Terry Halpin

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6    Some Data Model Patterns

This chapter discusses some data modeling patterns for dealing with temporal aspects of information systems (e.g. maintaining history of fact type populations and recording history of role subtype migration), as well as different kinds of collection structures (sets, ordered sets, bags, multisets, and sequences).

6.1    Temporal Aspects

Many data models involve object types that are temporal in nature. We distinguish between Instant (a point in time, e.g. 2015 November 14, 10:28 a.m. UTC), Duration (a length of time, e.g. 5 days) and Period (an anchored duration in time, e.g. 2015 November 15 .. 2015 November 20). The precision with which we record a temporal value is known as temporal granularity. For example, ...

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