  The original European ESPRIT ProCoS I and II projects on Provably Correct
Systems} took place around a quarter of a century ago. Since then the legacy of
the initiative has spawned many researchers with careers in formal methods. One
of the leaders on the ProCoS projects was Ernst-R\"udiger Olderog. This paper
charts the influence of the ProCoS projects and the subsequent ProCoS-WG
Working Group, using Prof. Dr Olderog as an example. The community of
researchers surrounding an initiative such as ProCoS is considered in the
context of the social science concept of a Community of Practice (CoP) and the
collaborations undertaken through coauthorship of and citations to
publications. Consideration of citation metrics is also included.
