1. A method of developing an interactive system performed by a computer system having data processing logic and computer readable storage media with one or more computer programs stored thereon, comprising using the computer system to: receive an application file including application data representative of an application for said system, said application data including operations and input and return parameters, with parameter types, for said application; generate a dialogue state machine, including a number of procedures with variables, on the basis of said application data, said state machine including slots for each operation and each input parameter, said slots defining data on which said interactive system executes the operations; generate prompts on the basis of said application data including a prompt listing said operations; generate grammar on the basis of said application data, said grammar including slots for each operation and input parameters to return data of said parameter types to said state machine; and execute grammatical inference to enhance the grammar on the basis of observations recorded by said system, including executing a model merging process that includes: processing rules of the grammar; creating additional rules representative of repeated phrases; and merging equivalent symbols of the grammar; wherein said rules define said slots and include said symbols.
14. A method as claimed in claim 1 , wherein said rules include a reference count representing the number of other rules that reference the rule.