From secured legacy systems to interoperable services (the careful evolution of the French tax administration to provide new possibilities while ensuring the primary tax recovering objective)

Abstract

The purpose of this paper is to describe the interest of opening legacy systems in large organisations instead of replacing them from scratch. The author also provides a feedback on the different REST solutions available to facilitate their usage by information technology architects. The paper underlines the importance not only to preserve the good functioning of the legacy heritage but also to migrate progressively applications to modernised languages. Assuredly, the code developed is robust and tackles the whole business perimeter whereas new technologies may suffer from a lack of stability or technical expertise within the organisation. This advocates for a progressive migration in the specific context of essential public services. To achieve the migration, the author proposes a hybrid architecture which relies on data exchanges between the legacy and modern parts of the application. Finally, a method is proposed to select an API management solution adjusted to each organisation requirements.