The Fourth Generation Language (4GL) functional model places 4GL in the context of programming language evolution, and describes the functions provided within the context. A 4GL is a software system that provides integrated functions for developing interactive on-line data processing applications. These functions are defined as: (1) user functions that define those services and capabilities necessary to provide a high level dialogue between the 4GL and users of the 4GL; (2) data management functions that provide capabilities to describe, store and retrieve, and perform ancillary tasks in the management and safekeeping of application data; and (3) system functions that provide the support services necessary to allow the user of 4GL to define and access applications in relation to the constraints of the 4GL's environment. A typical implementation of 4GL distributes pieces of these functions over various components, such as a DBMS, query language, data dictionary, screen formatter, report generator, and high level procedural language.
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