An introduction to clarity: a schematic functional language for managing the design of complex systems

Clarity is a functional schematic programming language currently freely available to the community‡‡http://www.sis.port.ac.uk/research/clarity/index.html.. It is a programming environment that allows a user to draw a program as a set of directed graphs. The term schematic is drawn from the traditions of engineering where the diagrams that represent electronic circuits or those of physical objects are often referred to as schematic drawings. A schema is a set of pictures or graphs that represent a program or working model. A schematic is taken as a system of tokens and structuring rules that expresses a program, model or concept; it is a graphical language. This paper introduces the principles behind design and issues to be considered when dealing with complex systems. The reasons why a “functional” representation provides a non-invasive approach to design and forms the basis of “good” design are described. In particular, the advantages of using diagrams is shown to be because the schema constructions make the structure of complex systems explicit as well as make a functional representation more intelligible than its sentential equivalent.