Hardware-software Co-design is a new discipline that provides methodologies and tools for the fast development of complex heterogeneous systems by combining hardware and software development cycles. This paper shows how the Propose&Revise PSM can be used to solve the hardware-software partitioning problem, the Co-design task that makes the decision on the best implementation of the different components of a system. In particular, a fuzzy expert system, SHAPES, has been developed following the CommonKADS methodology.