Behavioral subtyping and behavioral enrichment of multimethods

Multimethods can provide considerable flexibility to the OO (object oriented) designer. The authors' goal is to address issues related to reasoning about the behavior of multimethods. Specifically they show that the important notion of behavioral subtyping can be naturally extended to multimethods. The authors also investigate how, when reasoning about code that invokes multimethods, one can appeal to the enriched behavior provided by the specialized methods.