2.1 - Data models

``For data to be useful in providing information, they need to be organized so that they can be processed effectively. In data modelling we try to organize data so that:

they represent as closely as possible the real world
they are amenable to representation by computers.''

Components of a data model

Data models (Figure 2.1) have been introduced to help software developers to achieve these two potentially conflicting requirements. As stated by E.F. Codd in his 1981 Turing Award Lecture,

``A data model is a combination of at least three components:

a set of data structure types,
a collection of operators which can be applied to any instance of the data types, to retrieve, derive or modify data from any part of those structures in any combination desired,
a set of integrity rules, which define the consistent database states - these rules are general in the sense that they apply to any database using the model.''

Design advantage

A data model provides the designer and the programmer with substantial advantages: the detailed data design makes use of a few building blocks, and the manipulation of data is performed by a few operators that are the same for all data structures.

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BR and MR - CERN PTG - ADAMO Users Guide for Version 3.3 - 11 Oct 93