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Propagating New Information

The changes propagated by label propagation, as discussed in the previous section, are variable assignments as held in a traditional program store. However in this section we explore the application of constraint propagation to constraint stores, which maintain partial information about the program variables expressed as primitive constraints. Using a constraint store, it is possible to develop a quite different model of computation in which the store is never destructively changed by propagation, but only augmented. One great advantage of this combination is that confluence properties are easy to establish, and consequently there is little need for the programmer or applications designer to know in what order the propagation steps take place.

Mark Wallace
Wed Sep 3 18:36:40 BST 1997