1. A computer implemented method of processing user input to an information retrieval component within a computer wherein the computer implemented method includes a defining session between a user and an information retrieval component and an execution session between the user and an information retrieval component, the computer implemented method comprising: during the defining session: (a) receiving and storing a user generated definition of an expression type wherein the expression type is capable of being characterized as a (i) query seeking information from the information retrieval component, (ii) a statement seeking to add new information to the information retrieval component, and (iii) a command to perform an action, wherein the definition of the expression type specifies an expression format having a semantic structure, a response type, and a display format; during the execution session: (b) receiving a user generated expression having a semantic structure that matches a semantic structure that was received and stored during the defining session; (c) identifying an expression type for the received expression by determining: (i) whether the received expression semantically matches a command; (ii) whether the received expression is an answer to a question; (iii) whether a query of the information retrieval component using the received expression exactly as phrased results in identification of stored information associated with the received expression; and (iv) whether the received expression is an implicit command to add data to the information retrieval component; (d) processing the received expression according to the response type specified by the definition of the expression type for the received expression; and (e) causing a response to the received expression to be displayed to the user according to the display format specified by the definition of the identified expression type for the received expression.