  In this paper we apply the social network concept of core-periphery structure
to the sociotechnical structure of a software development team. We propose a
socio-technical pattern that can be used to locate emerging coordination
problems in Open Source projects. With the help of our tool and method called
TESNA, we demonstrate a method to monitor the socio-technical core-periphery
movement in Open Source projects. We then study the impact of different
core-periphery movements on Open Source projects. We conclude that a steady
core-periphery shift towards the core is beneficial to the project, whereas
shifts away from the core are clearly not good. Furthermore, oscillatory shifts
towards and away from the core can be considered as an indication of the
instability of the project. Such an analysis can provide developers with a good
insight into the health of an Open Source project. Researchers can gain from
the pattern theory, and from the method we use to study the core-periphery
movements.
