objects provide the useful abstraction in programming languages. views provide a similar abstraction in databases. Since databases provide for persistent and shared data storage, view concepts will avoid problems occurring when persistent objects are to be shared.
database concepts provide independence of storage and user data formats. The schema describes the form of the database contents, …, querying the shared database using nonprocedural declaration of the forms:
SELECT what-I-want WHERE some-set-of-conditions-is-true
The principle formal database mechanism to obtain selected data for an application is a view spec. Having pre-defined views simplifies the user’s access and can also restrict the user from information that is to be protected.
views … closer to objects: related data has been brought together. The use of objects permits the programmer to manipulate data at a higher level of abstraction … Especially attractive is the display capability associated with objects. Object concepts can of course be implemented using non-specialized lang.
The collection of the tuples of a view is defined by the query that generates the set, and described by the relation schema and associated with the view query.