data model
data modelling

    The product of the database design process which
   aims to identify and organize the required data logically and
   physically.

   A data model says what information is to be contained in a
   database, how the information will be used, and how the items
   in the database will be related to each other.

   For example, a data model might specify that a customer is
   represented by a customer name and credit card number and a
   product as a product code and price, and that there is a
   one-to-many relation between a customer and a product.

   It can be difficult to change a database layout once code has
   been written and data inserted.  A well thought-out data model
   reduces the need for such changes.  Data modelling enhances
   application maintainability and future systems may re-use
   parts of existing models, which should lower development
   costs.

   A data modelling language is a mathematical formalism with a
   notation for describing data structures and a set of
   operations used to manipulate and validate that data.

   One of the most widely used methods for developing data models
   is the entity-relationship model.  The relational model is
   the most widely used type of data model.  Another example is
   NIAM.

   ["Principles of Database and Knowledge-Base Systems",
   J.D. Ullman, Volume I, Computer Science Press, 1988, p. 32].

   (2000-06-24)