Abstract Restraining the combinatorial flood of conceivable solutions to chemical problems by formal means is discussed. An algebraic model of the logical structure of constitutional chemistry not only serves as the theoretical foundation of the inference engines in strictly logic-orientated chemical computer programs, but also provides a conceptual framework for non-arbitrary, transparent procedures for reducing the combinational abundance of conceivable solutions to given chemical problems. Diverse procedures are available to provide efficient guidance on routes from a chemical problem to its chemically most meaningful solutions. The division of problems into subsidiary problems, the bilateral alternative to monolateral approaches, and the hierarchic classification of results, prior to selecting individual solutions, is highly effective in computer-assisted problem-solving.