FPP is a modeling language for the F Prime flight software framework. To use FPP, you write a model in the source language; then you use the FPP tools to generate XML and C++. Compared to writing XML by hand, FPP provides a cleaner and more succinct syntax, a well-defined semantics, good error checking and reporting, and better integration between the model and the generated code.
For more information on FPP, see the following resources: