Some Reflections on Knowledge Based System Modeling - Mathematical Aspects: Applications to Symbolic (and Geometric) Modeling of Robot Arms Jochen Pfalzgraf Computer Science Institute University of Salzburg Salzburg, Austria In this contribution we would like to embed the topic of the special session "ACA in Robotics" in a larger framework as indicated in the title. First we present some thoughts about knowledge based systemmodeling (``almost everything'' is knowledge based modeling ...) from a mathematical perspective (general aspect: looking for ``the right'' language to formulate a given problem and try to solve it). Then we focus on modeling robot arms as kinematic chains and discuss mathematical and symbolic computation aspects which arise naturally in that field.