One natural criterion is the following. We could say that a response to a question counts as a proper answer just in case it resolves the issue that the question raises. If we adopt this criterion then we also have to impose a certain structural condition on question-meanings. That is, question-meanings cannot just be defined as arbitrary sets of propositions, as in the theories of Hamblin (1973) and Karttunen (1977). Rather, they should be defined as downward closed sets of propositions. That i