
114 Chapter 6 Planning-Graph Techniques
through a disjunction of resolvers. Because in general flaws are not independent
and their resolvers may interfere, dependency relations are posted as constraints to
be dealt with at a later stage.
Disjunctive refinement may not appear right away to the reader as the main
motivation in planning-graph techniques. However, reachability analysis is clearly
a driving mechanism for these approaches. Let us detail its principles and
the planning-graph structure (Section 6.2) before getting into planning-graph
algorithms (Section 6.3).
6.2 Planning Graphs
The planning-graph structure provides an efficient way to estimate ...