The paper describes how a language analyser (parser) is used as interface between a user and the functions of an information system. A specific user is at log-on forced into a sublanguage analyser, which only recognizes statements relevant to this specific user. Every attempt to use non-allowed functions is rejected, and the user is guided into his sublanguage. The language analyser is defined completely separately from the semantics of the information system, and it can be automatically generated outgoing from a definition of language functions.