If we have an estimation r X (j) of the optimal score for translating position j, then the value of the heuristic function R X (n) for a node n can be inferred by summing over the contribution for every position j that is not in the coverage vector c(n) (here X denotes different possibilities to choose the heuristic function): The situation in the case of the alignment template approach is more complicated, as not every word is translated alone, but typically the words are translated in context.
the basic quantity for the heuristic function in the case of the alignment template approach is a function r(Z) that assigns to every alignment template instantiation Z a maximal probability.