Data model: Difference between revisions

Revision as of 16:07, 27 January 2003

Revision as of 16:23, 27 January 2003

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# ''Querying:'' provides a language in which the data can be queried.

An example is the [[relational model]] in which the structure ofall data is definedrepresented by as

[[mathematical relation]]s. (or, to be precise, a slightly generalized version thereof).
It furthermore defines a set of specific constraints ([[candidate keyskey]]s, [[foreign keys, functional dependencies, multi-valued dependencies, join dependencieskey]]s) 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 [[Entity-Relationship Model]] and [[ORM]] although these usually only describe a small subset of the aspects described above.