The well formed nature of this system leads to some potential developments. One of the most exciting would have to be the possibility of adding user interaction. If a plan step is rejected, or the planner is unable to complete a plan, a human user could construct a plan step manually (like decision table rule entry in Hullenkremer [1985]). A new rule could be induced from this plan step, or old rules could be altered. This would allow a system that could be operated without the use of a knowledge engineer to develop the rules. In a slightly different approach, Lu and Zhang [1989] have developed a system that will induce rules from detailed process models. This could also be a novel approach to developing rule sets.

Variant planning does not always receive the recognition it deserves. The benefits of Variant planning are the fast setup times, ease of use, and the ability to deal with plans that are highly specific to a factory or technology. There has been research in the past trying to match CSG representations to GT codes [Kakazu and Okino, 1984]. Using this approach GT codes could be developed for products and parts, then products and parts could be found with similar codes, and their plans recalled and edited. There is also work being done to categorize parts to drive a generative planner [Iwata et. al., 1987].

Developing a CAD system for the design structure would create some possibilities for the addition of some other techniques, such as,

• automatic dimensioning as is done in Yuen et. al. [1988] who chain up dimension dependencies. Work has also been done by Minagawa et. al. [1986],

• addition of functional modelling as is found in Kiriyama et. al. [1991],

• use of CAPP as a concurrent engineering tool [Domazet and Lu, 1991,92]

Other systems may also be added for process plan verification, and operation planning. There is work about the topic in high level terms [Peklenik, 1990] but in more specific terms some possible approaches are listed below,

• assembly sequence planning is of great value. deMello and Sanderson [1991 a, b], Heemskerk [1989], Laperriere and ElMaraghy [1992], Baldwin et. al. [1991], Tonshoff et. al. [1992] suggest such a system. Systems for Disassembly planning have also been done by Lee et. al. [1992].

• automatic generation of NC tool paths. Tsai et. al. [1991], Kao et. al. [1990], Cavendish and Marin [1992], Parkinson [1986], Su and Mukerjee [1991] describe systems to do this,

• automatic generation of NC code for machine forging dies [Eversheim and Cobanoglu, 1989].

• fixture planning, such as the work of Nee et. al. [1992],

• database lookup - such as that for metal forming by Raj and Kumar[1990],

• models of specific processes to verify operations like non-linear optimization for Electro-Discharge Machining (EDM),

• modules for sheet metal bending [Huwiler and Reissner, 1992],

• planning for connecting joints [Neiminen et. al., 1989].

• The problem of mapping from design to production has not been examined formally but it might reveal some interesting results in the context of this thesis.