A visual programming language for qualitative data

Modeling of human knowledge and reasoning requires the formulation of uncertainty in its various forms. Fuzzy logic was introduced to directly support these applications (H. Zimmermann, 1991). Fuzzy control (FC) which is based on fuzzy logic allows one to control complex systems based on qualitative information like human knowledge (C. Geiger and G. Lehrenfeld, 1994). In fuzzy logic, fuzzy sets are usually defined and manipulated by means of complex mathematics, whereas the fuzzy control process is frequently outlined by visual sketches based on set diagrams in order to enhance the comprehension of the inference process. The rule based execution of this process usually follows the lines of rule based visual programming languages (VPLs), i.e., languages comparable to Agentsheets and ChemTrains. This strongly indicates that VPLs are thus well applicable for this use. We first outline the basic concepts of fuzzy logic and fuzzy control. Thereafter, we sketch a visual language which integrates fuzzy set diagrams in the visual representation of rules. The basic concepts are inherited from the complete visual programming language, Pictorial Janus (PJ). However, we significantly simplify PJ's visual concepts in order to adapt it for our purpose.