GVL: a graphical, functional language for the specification of output in programming languages

The conceptual view model of output is based on the complete separation of the output specification of a program from the program itself, and the use of implicit synchronization to allow the data state of the program to be continuously mapped to a display view. An output specification language called GVL is used to specify the mapping from the program´s data state to the display. GVL is a functional language explicitly designed for specifying output. Building from a small number of basic primitives, it provides sufficient power to describe complex graphical output. Examples, including GVL specifications for linked list diagrams, bar charts and an address card file, are given. In keeping with its intended application, GVL is also a graphical language, in which the user draws output specifications directly on the display. How problems often associated with imperative graphical languages are avoided by using the functional paradigm is shown. A prototype implementation of GVL was used to produce examples of graphical output