Evolution and maintainability of legacy systems is all time attention drawing subject for researchers and especially practitioners. Discovering the crosscutting concerns and separating it from core functionalities of a software system may help in evolution of the legacy systems. Aspect-oriented software development (AOSD) tries to achieve the goal. AOSD is new programming paradigm which helps to bring in modularity in the program by writing the crosscutting concerns in the form of ‘aspects'. Modularity brings comprehensibility and hence maintainability of the software system. Tools and techniques, which aid in identifying the crosscutting concerns in such systems and refactoring them into aspects, are needed to apply aspect-oriented techniques to legacy systems at use in industry. This chapter aims to identify issues, problems and approaches used in the migration from legacy systems to aspect-oriented software system.
