The paper presents a knowledge representation form (KRF) oriented to k
nowledge based CAD systems development for variant design in mechanica
l engineering. It combines both declarative knowledge (frames and prod
uction rules) and procedural knowledge. From this KRF, a design proble
m solving method based on a data driven inference process has been dev
eloped. A way to automate the knowledge acquisition process according
to this KRF is defined.