Configuration systems[B 1][A 1][A 2] or also referred to as configurators or mass customization toolkits,[A 12] are one of the most successfully applied Artificial Intelligence technologies. Examples are the automotive industry,[A 9][B 5] the telecommunication industry,[A 7] the computer industry,[A 6][A 13] and power electric transformers.[A 8] Starting with rule-based approaches such as R1/XCON,[A 6] model-based representations of knowledge (in contrast to rule-based representations) have been developed which strictly separate product domain knowledge from the problem solving one - examples thereof are the constraint satisfaction problem, the Boolean satisfiability problem, and different answer set programming (ASP) representations. There are two commonly cited conceptualizations of configuration knowledge.[A 3][A 4] The most important concepts in these are components, ports, resources and functions.