11. A method for generating a translation rule to support natural language search, comprising: receiving a first natural language expression and a second natural language expression, the first expression being semantically different from the second expression; generating a first representation by parsing the first expression; generating a second representation by parsing the second expression, the first representation and the second representation each comprising word facts and roles; determining aligned pairs based on the first semantic representation and the second semantic representation; replacing, in the first representation and the second representation, variables that correspond to the aligned pairs with a generic variable; upon replacing the variables that correspond to the aligned pairs with the generic variable, removing the word facts from the first representation and the second semantic representation that that occur in both the first and second representation; upon removing the word facts that correspond to the replaced variables, replacing the remaining word facts in the first representation with a broader representation of the word facts; and upon replacing the remaining word facts in the first representation with the broader representation, generating the translation rule including the first representation, an operator, and the second representation.
11. A method for generating a translation rule to support natural language search, comprising: receiving a first natural language expression and a second natural language expression, the first expression being semantically different from the second expression; generating a first representation by parsing the first expression; generating a second representation by parsing the second expression, the first representation and the second representation each comprising word facts and roles; determining aligned pairs based on the first semantic representation and the second semantic representation; replacing, in the first representation and the second representation, variables that correspond to the aligned pairs with a generic variable; upon replacing the variables that correspond to the aligned pairs with the generic variable, removing the word facts from the first representation and the second semantic representation that that occur in both the first and second representation; upon removing the word facts that correspond to the replaced variables, replacing the remaining word facts in the first representation with a broader representation of the word facts; and upon replacing the remaining word facts in the first representation with the broader representation, generating the translation rule including the first representation, an operator, and the second representation. 13. The method of claim 11 , wherein determining aligned pairs based on the first representation and the second representation comprises: matching variables in the first representation with variables in the second representation that correspond to the same word; and upon matching the variables in the first representation with the variables in the second representation that correspond to the same word, matching the remaining variables in the first representation with the remaining variables in the second representation based on induction.