Classical software engineering has been traditionally dominated by stand-alone development organizations and collaborations be- tween contractors, integrators and suppliers. The notion of software ecosystems has been established as a new kind of software engineer- ing paradigm in the last decade. In its essence it proposes participative engineering across independent development organizations.
This short paper reviews the current state-of-the-art and presents a typification of successful software ecosystems. We further discuss key characteristic of the ecosystem types and present a set of example cases. The characterization reviews and consolidates existing research and discusses variations within the key building block of a software ecosystem. It further enables sharpening the borders of what an ecosystem is (and what not) and how the individual types can be differentiated. Thus, this paper contributes to widening the understanding of software ecosystems.