Context: Most companies, independently of their size and activity type, are facing the problem of managing, maintaining and/or replacing (part of) their existing software systems. These legacy systems are often large applications playing a critical role in the company's information system and with a non-negligible impact on its daily operations. Improving their comprehension (e.g., architecture, features, enforced rules, handled data) is a key point when dealing with their evolution/modernization. Objective: The process of obtaining useful higher-level representations of (legacy) systems is called reverse engineering (RE), and remains a complex goal to achieve. Socalled Model Driven Reverse Engineering (MDRE) has been proposed to enhance more traditional RE processes. However, generic and extensible MDRE solutions potentially addressing several kinds of scenarios relying on different legacy technologies are still missing or incomplete. This paper proposes to make a step in this direction. Method: MDRE is the application of Model Driven Engineering (MDE) principles and techniques to RE in order to generate relevant model-based views on legacy systems, thus facilitating their understanding and manipulation. In this context, MDRE is practically used in order to 1) discover initial models from the legacy artifacts composing a given system and 2) understand (process) these models to generate relevant views (i.e., derived models) on this system. Results: Capitalizing on the different MDRE practices and our previous experience (e.g., in real modernization projects), this paper introduces and details the MoDisco open source MDRE framework. It also presents the underlying MDRE global methodology and architecture accompanying this proposed tooling. Conclusion: MoDisco is intended to make easier the design and building of modelbased solutions dedicated to legacy systems RE. As an empirical evidence of its relevance and usability, we report on its successful application in real industrial projects and on the concrete experience we gained from that.

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