Example 2: KWIC — index generation
A method of program specification is described which leads naturally to the expression of a program as a network of simple processes. Starting with the problem statement the valid inputs and outputs of the system are specified by grammars which represent the structure of the input and output streams of a "black-box" which can be decomposed hierarchically into a structured network of processes which performs the required transformations. Three forms of network structure are described, analagous to the three forms of control in sequential programs. The leaves of the hierarchical description are sequential processes described by a form of attributed translation grammar which permits the specification of semantic as well as syntactic transformations. The notation can be used to specify programs which may be implemented either in conventional programming languages or by direct compilation of the DTL notation. The method is illustrated by application to the KWIC index workshop example.
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