Figure 23. The family entailments among the B, V, C, R, and Sym relations. Double-line arrows stand for the entailments (such as V => B); single solid lines indicate the possible coexistence of relations which do not entail each other (such as V – C), and dashed lines serve to remind that the entailments do not go both ways (V and C both entail B, but B does not necessarily entail either V or C)