The basic theory behind solid modelling was reviewed, including the fundamental operators. Of particular interest was the Assembly operator. While it was shown that there are currently no satisfactory techniques for assembly modelling, it was made clear that techniques are evolving.

The product representation was presented, including a basic structure, and details necessary for a computer implementation. The representation includes data structures capable of storing and manipulating Boolean equations. These equations also refer to sets of properties. The final data structure was selected in such a way that the method of representation (r-sets/s-set/CNRG/etc.) did not have to be chosen. This can be said because at no point is the data structure interpreted physically, thereby forcing a selection of representation.

There are a number of highlights from various sections of this chapter.

• The attributes of sets, such as tolerances, have been left undefined to allow for the greatest flexibility in future use. (Only a few very fundamental properties have been defined, such as position).

• The computer was able to generate a graphical representation of the part based upon the part file. This indicates that the method is at least sufficient for geometrical representation.

• The nested Boolean form has been used to eliminate ambiguities in operator scope.

• Properties may be appended to sets and primitives. This allows reuse of basic parts as would be desired in an Engineering design environment.

• Most of the common Boolean algebra axioms are included in the equation manipulation subroutines.