By using Boolean equations, and sets to represent designs, it has been shown to be possible to generate process plans. The process plans have a number of features of interest,

- multiple manufacturing domains are considered,

- cost can be considered,

- sequencing is somewhat inherent, although not required,

- even without interpreting the product geometry, the system is able to suggest process plans.

The input form used by the planner does not contain unreasonable knowledge that would not normally be available from a CAD system. This information is processed by a non-linear, hierarchical process planner. The hierarchical representation of knowledge is based upon high-level examination of design equations for recognized equation forms and then subsequent application of more traditional production rules. The process planner can handle non-linear cases by backtracking from failed states. The example cases showed a number of successful applications to process planning situations. In the next section some of the outstanding issues will be discussed in terms of future work.