Most of the legacy software systems were developed in imperative languages with traditional design approaches. Instead of continually maintaining these legacy systems at high cost, re-engineering them to new systems with good design and architecture can surely improve their understandability, reusability and maintainability. Design patterns (DPs) have integrated the concept of standardization and expert experiences into a set of inter-related components that can function certain behaviors with better flexible structure. The software development with DPs provides easier understanding and standardization that makes the system evolution much more effective. We use a parallel program generation environment (PPGE) as a case study to the re-engineering of a traditional software system into a pattern based software system. An architecture with the Dynamic-Packing Component Library (ADPCL) which is composed of existing well-known design patterns, and a pattern based re-engineering approach for transformation systems are also proposed.
