Logical data model
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In computer science, a logical data model is a representation of an organization's data, organized in terms of a particular data management technology. When ANSI first laid out the idea of a logical schema (in 1975 [1]), the choices were hierarchical and network. Relational had just been recognized as a data organization theory but no technology existed. Now, the choices are relational, object-oriented, and XML. Relational data are described in terms of tables and columns. Object-oriented data are described in terms of classes, attributes, and associations. XML is described in terms of tags.
Logical data models, properly designed, should be based on the structures identified in the conceptual data model. This, after all described the semantics of the business, which the logical model should also reflect. Even so, since the logical data model anticipates implementation on a finite-capacity computer, some will modify the structure to achieve certain efficiencies.
This is sometimes incorrectly called a "physical data model", which is not what the ANSI people had in mind. The physical design of a database involves deep use of particular database management technology. For example, a table/column design could be implemented on a collection of computers, located in different parts of the world. That is the domain of the physical model.
[edit] Reference
1. American National Standards Institute. 1975. “ANSI/X3/SPARC Study Group on Data Base Management Systems; Interim Report”. FDT(Bulletin of ACM SIGMOD) 7:2.
