The Free On-line Dictionary of Computing (30 December 2018):
The product of the database design process which
aims to identify and organize the required data logically and
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
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
["Principles of Database and Knowledge-Base Systems",
J.D. Ullman, Volume I, Computer Science Press, 1988, p. 32].