Our parsing algorithm produces all possible parses from an ambiguous sentence. For the algorithm to be useful in practical applications, we need a mechanism to select one intended parse out of a batch of parses. In theory, it is desirable for the system to be able to disambiguate a sentence by semantics and pragmatics, and a large number of techniques using semantic information have been developed to resolve natural language ambiguity [13, 45, 7]. In practice, however, not all ambiguity problems can be solved by those techniques at the current state of the art. Moreover, some sentences are absolutely ambiguous, that is, even a human cannot disambiguate them, unless he knows the intent of the speaker.