A method for controlling a relational database system, wherein a query statement to be processed, which consists of keywords, is first analyzed by applying a recursive transition network (RTN) and then converted into control commands by the following steps: defining the RTN in a presetting step by forming independent RTN building blocks each having an inner, directed decision graph and optionally at least one recursive call function; forming an RTN building block-independent reference group, the elements of which refer to a residual decision graph with the first decision position removed; carrying out a reference processing step and running the residual decision graphs, which may prescribe the recursive call function; and generating an optimized access plan for the relational database system.