21.5 Resolving Goal Interactions 499
To avoid looking at every FBM, IMACS does a depth-first branch-and-bound
search to generate and test FBMs one at a time, pruning unpromising FBMs as
described in Section 21.8. To measure how good a plan is, IMACS uses an estimate
of the plan’s manufacturing time, as described in Section 21.7. A better measure
would also incorporate estimates of production cost: this was not done in IMACS
because IMACS is a prototype, but it would be straightforward to accomplish.
As an example of how much the branch-and-bound search reduces the size of
the search space, IMACS generates only 16 of the 512 FBMs for the socket P
0
.
21.5 Resolving Goal Interactions
An FBM corresponds to a set of tasks in which no ordering constraints