Data model

A data model is a model that describes in an abstract way how data is represented in an information system or a database. In general it describes the following aspects:

1. Structure: defines what the structure of the representation is. This should not only specify how data is represented but also how a schema can be specified that defines the structure of the data in a specific user domain.
2. Integrity: provides a language for the definition of rules that restrict which instances of the defined structure are allowed.
3. Manipulation: provides a language in which updates of the data can be expressed.
4. Querying: provides a language in which the data can be queried.

An example is the relational model in which all data is represented by mathematical relations (or, to be precise, a slightly generalized version thereof). It furthermore defines a set of specific constraints (candidate keys[?], foreign keys) and a general language for specifying constraints (first-order logic), and for manipulations and querying the data the relational algebra, tuple calculus and domain calculus are introduced.

Other examples are the Functional Data Model[?], the Entity-Relationship Model[?] and the Object Role Model[?] although these usually only describe a small subset of the aspects described above.