Evolving legacy systems through a multi-objective decision process

Our previous work on improving the quality of object-oriented legacy systems includes: i) devising a quality-driven re-engineering framework (L. Tahvildari et al., 2003); ii) proposing a software transformation framework based on soft-goal interdependency graphs to enhance quality (L. Tahvildari and K. Kontogiannis, 2002); and iii) investigating the usage of metrics for detecting potential design flaws (L. Tahvildari and K. Kontogiannis, 2004). This paper defines a decision making process that determines a list of source-code improving transformations among several applicable transformations. The decision-making process is developed on a multi-objective decision analysis technique. This type of technique is necessary as there are a number of different, and sometimes conflicting, criterion among non-functional requirements. For the migrant system, the proposed approach uses heuristic estimates to guide the discovery process