This chapter outlines a number of issues on enterprise design architectures suitable for applications that need flexibility and change in their design. Better understanding of user requirements is needed to reflect the best performance of the system towards its users. Verifying the requirements elicited for best system performance is an essential task for enterprise systems design. The requirements elicited should reflect the user intention, as he/she has demanded. This chapter presents some of the international Lyee project’ results led by Fujita (Fujita 2001) and is structured into two parts: one part reflects the collaborative intention outcome and the other part is related to legacy software outcome. The 1st part shows the impact of correct requirements on enterprise design architectures; it also enlists some of the results achieved by our project. The 2nd part shows the impact of Legacy software using new techniques extracted from an intention-oriented tool, namely Lyee builder. This second part also contributes in showing new techniques for handling legacy software, an issue that is important for handling essential problems related to old generation software, which is our current interest. We have succeeded to build a software diagnosis tool based on the Lyee framework, which is currently used in business practices to diagnose programs written in imperative languages.