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Designing Software for Ease of Extension and Contraction
March 1979 (vol. 5 no. 2)
pp. 128-138
D.L. Parnas, Information Systems Staff, Communications Sciences Division, Naval Research Laboratory
Designing software to be extensible and easily contracted is discussed as a special case of design for change. A number of ways that extension and contraction problems manifest themselves in current software are explained. Four steps in the design of software that is more flexible are then discussed. The most critical step is the design of a software structure called the " uses" relation. Some criteria for design decisions are given and illustrated using a small example. It is shown that the identification of minimal subsets and minimal extensions can lead to software that can be tailored to the needs of a broad variety of users.
Index Terms:
supersets, Contractibility, extensibility, modularity, software engineering, subsets
Citation:
D.L. Parnas, "Designing Software for Ease of Extension and Contraction," IEEE Transactions on Software Engineering, vol. 5, no. 2, pp. 128-138, March 1979, doi:10.1109/TSE.1979.234169
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