Abstract: A system and method are provided for processing a document containing multiple words to extract an answer. The method uses a set of signatures and signature based rules. Each rule includes a name formed by concatenating the signatures included in the rule and a concept which is assignable to the combination of signatures included in the rule. The method parses the words and assigns a signature to each of them. It may also assign a window which includes a parameter defining the number of signatures viewable at one time. The window may be moved so that the window reveals signatures not viewable in its previous position. The signatures viewable in the window are read and a rule name is created by concatenating the signatures. The created rule name is compared to the names of the rules and, if the created name matches any of the rule names, the matching rule is applied to create a concept and the concept is assigned back into the window.