Many new designs are modifications, derivations, or variations of existing designs. The problem of redesign is a fruitful area for research both because the problem is better defined than for de novo design and because redesign is common in practice. One approach to the problem of redesign in the use of replay, that is, re-creating the steps by which the original design was created and modifying the original decisions to meet the new requirements. This proposal addresses reusability of a design by transforming a formal specification of the problem into a suitable implementation by the repeated application of transformations. It explores how a specification derived as a modification of an existing design can be realized by replaying the transformational derivation of the original and modifying it as required by changes made to the specification. This notion of replay can substantially mediate the difficulty and expense of maintenance, particularly for software systems. The Principal Investigators propose to exhibit a replay capability for a transformational system that designs efficient data structures. The PIs have previously developed a suitable set of transformations for this domain and have powerful knowledge-based tools to support this activity.
