For the sake of convenience, in this section we assume M is a meta-grammar M = {m}, where each m represents a meta-rule.
for each translation r, there exists a hypergraph H r that represents all possible derivations D r = {d} that can generate rule r. Here, each derivation d is a hyperpath using meta- we can use hypergraph H r to characterize r. Translation rules in G can share nodes and meta-rules in their hypergraphs, so that M is more compact model than G. In the rest of this section, we will introduce three methods to quantify H r as features of rule r. It should be noted that there are more ways to exploit the compact model of M than these three.