  Although architecture instability has been studied and measured using a
variety of metrics, a deeper analysis of which project parts are less stable
and how such instability varies over time is still needed. While having more
information on architecture instability is, in general, useful for any software
development project, it is especially important in Open Source Software (OSS)
projects where the supervision of the development process is more difficult to
achieve. In particular, we are interested when OSS projects grow from a small
controlled environment (i.e., the cathedral phase) to a community-driven
project (i.e., the bazaar phase). In such a transition, the project often
explodes in terms of software size and number of contributing developers.
Hence, the complexity of the newly added features, and the frequency of the
commits and files modified may cause significant variations of the instability
of the structure of the classes and packages. Consequently, in this registered
report we suggest ways to analyze the instability in OSS projects, especially
during that sensitive phase where they become community-driven. We intend to
suggest ways to predict the evolution of the instability in several OSS
projects. Our preliminary results show that it seems possible to provide
meaningful estimations that can be useful for OSS teams before a project grows
in excess.
