1. A method in a computer system for generating information retrieval tokens from an input string, the method comprising the steps of: creating from the input string a primary logical form characterizing a semantic relationship between selected words in the input string; identifying hypernyms of the selected words in the input string, at least one hypernym being identified from a group of hypernyms associated with a selected word wherein at least one other hypernym in the group is not identified; constructing from the primary logical form one or more alternative logical forms, each alternative logical form being constructed by, for each of one or more of the selected words in the input string, replacing the selected word in the primary logical form with an identified hypernym of the selected word; and generating tokens representing both the primary logical form and the alternative logical forms, the generated tokens being distinguishable by an information retrieval engine.