1. A system for recognizing user input to a computer from a user input device, comprising: input means for receiving user input data in the form of a signal from a user input device chosen from the group consisting essentially of a tablet input device and a voice input device; means for storing said user input data in memory of said computer system; a hierarchy of independent recognition domains, each of said hierarchy of independent recognition domains comprising group means and classify means, including: a first recognition domain for receiving a portion of said user input data as a first recognition domain input and performing character-related recognition on the user input data only if the user input data is of the type expected in a screen recognition area and generating one or more active character-related hypotheses, each of said active character-related hypotheses comprising a portion of said user input data together with a character-related interpretation of said user input data; a second recognition domain for receiving at least one of said active character-related hypotheses as a second recognition domain input and performing word-related recognition on the user input data only if the user input data is of the type expected in said screen recognition area and generating one or more active word-related hypotheses, at least one of said active word-related hypotheses being derived from said one of said active character-related hypotheses; a third recognition domain for receiving a portion of said user input data as a third recognition domain input and performing shape part recognition on the user input data only if the user input data is of the type expected in said screen recognition area and generating one or more active shape-pan-related hypotheses, each of said shape-part-related hypotheses comprising a portion of said user input data together with a shape-part-related interpretation of said user input data; and a fourth recognition domain for receiving at least one of said active shape-part-related hypotheses as a fourth recognition domain input and performing shape recognition on the user input data only if the user input data is of the type expected in said screen recognition area and generating one or more active shape-related hypotheses, at least one of said active shape-related hypotheses being derived from said one of said active shape-part-related hypotheses; means for storing said active hypotheses in a database comprising a piece pool and a unit pool in said memory of said computer system; a control unit including: first control means for managing the means for storing active hypotheses, said first control means further including means for removing a previously stored hypothesis from said database, said means for removing further removes a hierarchy of hypotheses from which said previously stored hypothesis is derived, down to constituent strokes as well all other hypotheses in said database that refer to said constituent strokes; and second control means for scheduling the recognition tasks in said recognition domains; arbiter means for resolving multiple active hypotheses from said recognition domains and choosing a recognition result among said multiple active hypotheses from said recognition domains; and a user output device for communicating to said user said recognition result.