Abstract: A logic method for accessing rules in a logic circuit synthesis system. Application of rules in a data base results in replacement of one or more model instances with other model instances or in alteration of values associated with the model instances or in the alteration of parameter values in the data base. Model instances are designated as VISIBLE or INVISIBLE, INVISIBLE model instances are ignored during logic circuit synthesis. VISIBLE model instances may be NEW or INACTIVE. All VISIBLE model instances are initially NEW. If no rule assciated with a model instance is TRUE, the model instance becomes INACTIVE. If at least one rule associated with a model instance is TRUE, one or more model instances are replaced and all inserted model instances and model instances directly connected to the inserted model instances become NEW. The number of model instances a rule will replace is called a SIZEWIN value of the rule.