There may be a simple generic way to correct pic's habit of accepting any set of object modifiers on any object, but obeying only a compatible subset. Pic already collects a bit vector of modifier types attached to the current object. If that were extended with a few more bits that designate the object types, the size, B, of the bit vector would be about 35--an easy fit in one 64-bit word. Then a BxB bit matrix could record both modifier/modifier incompatibilities and object/modifier incompatibilities. The collected bit vector needs to be tested against the matrix once per object definition. It seems to be harder to catch duplication of modifiers, requiring extra code at all points where bits are set. Nevertheless, this kind of error also merits detection. Some questions Does anybody think the issue is not worth addressing? Is there a better scheme than that suggested above? Is the scheme adequate? It would not, for example, catch a three-way incompatibility that does not entail any pairwise incompatibility, should such an incompatibility exist. Any other thoughts? Doug