13. The system of claim 11 , wherein the operations further comprise: receiving an expression in the second natural language; using the second machine translator, translating at least a portion of the expression from the second natural language to a canonical representation of the at least a portion of the expression; and using a third machine translator, translating the canonical representation of the at least a portion of the expression into an equivalent expression in a third natural language.
11. The system of claim 8 , wherein the operations further comprise: training the second machine translator, using the set of training data, to translate acceptable expressions for a value of the variable entity in the second natural language to corresponding canonical representations.