General function structures consist of symbols for energy flow, material flow, and information flow as well as their conversion. They are used to abstractly depict a system's functions without specifying the respective implementation. That way, already existing systems can be analyzed for the adaptive design. When developing a new design, a general function structure is created from the requirements.
Varying the general functions structure can lead to new functional solutions. This works for both adaptations and new designs. Additionally, general function structures can help dividing problems into subtasks.