In previous work we described how the process algebra based language PSF can be used in software engineering, using the ToolBus, a coordination architecture also based on process algebra, as implementation model. We also described this software development process more formally by presenting the tools we use in this process in a CASE setting, leading to the PSF-ToolBus software engineering environment. In this article we summarize that work and describe a similar software development process for implementation of software systems using a client / server model and present this in a CASE setting as well.