This makes it difficult to incorporate semantic parsing into SMT merely by applying the sort of dynamic programming techniques found in current syntactic and tree-structured SMT models, most of which rely on being able to factor the computation into independent computations on the subtrees.
the key computational obstacle is that the semantic parse of a larger string (or string pair, in the case of translation) is not in general strictly mechanically composable from the semantic parses of its smaller substrings (or substring pairs).