19. The computer-readable storage medium of claim 18 , having further computer-executable instructions stored thereon which, when executed by a computer, cause the computer to apply the translation rule during content acquisition to convert a semantic representation of a search result that is stored in a semantic index, the semantic representation matching the first semantic representation.
18. A computer-readable medium having computer-executable instructions stored thereon which, when executed by a computer, cause the computer to: receive a first expression and a second expression, the first expression being semantically different from the second expression; generate a first semantic representation by parsing the first expression; generate a second semantic representation by parsing the second expression, the first semantic representation and the second semantic representation each comprising word facts and roles, the roles identifying relationships between the word facts; determine aligned pairs based on the first semantic representation and the second semantic representation; replace, in the first semantic representation and the second semantic representation, variables that correspond to the aligned pairs with a generic variable by matching variables in the first semantic representation with variables in the second representation that correspond to the same word and by matching the remaining variables in the first semantic representation with the remaining variables in the second semantic representation based on induction; upon replacing the variables that correspond to the aligned pairs with the generic variable, remove the word facts from the first semantic representation and the second semantic representation that correspond to the replaced variables; upon removing the word facts that correspond to the replaced variables, replace the remaining word facts in the first semantic representation with a broader representation of the word facts; and upon replacing the remaining word facts in the first semantic representation with the broader representation, generate a translation rule including the first semantic representation, an operator, and the second semantic representation.