Rigorous Methods for Software Construction and Analysis

Egon B¨ orger Tribute to Egon B¨ orger on th the Occasion of his 60 Birthday 1 2 Jean-Raymond Abrial and Uwe Glasser ¨ 1 jrabrial@neuf. fr 2 glaesser@cs. sfu. ca Egon B¨ orger was born on May 13, 1946, in Westfalia (Germany). After the cl- sic baccalaur´ eat, from 1965-1971 he studied philosophy, logic and mathematics at the Sorbonne (Paris, France), Institut Sup´ erieur de Philosophie de Louvain (Belgium), Universit´ e de Louvain and Universitat ¨ Munster ¨ (Germany), where he got his doctoral degree and in 1976 his “Habilitation” in mathematics. The themes of his doctoral dissertation,ReductionclassesinKromandHornfor- lae,andofhis“Habilitationsschrift,”Asimple method for determining thedegree of unsolvability of decision problems for combinatorial systems,havetheirroot inthe computationalviewofmathematicallogicheldatthe time atthe Institute for Logic and Foundations of Mathematics at the University of Mu ¨nster, a t- dition going back to (among others) Leibniz, Ackermann, G¨ odel, Post, Turing, Kleene, and associated in Munster ¨ with the names of the founder of the ins- tute, Heinrich Scholz, and his followers Hans Hermes, Gisbert Hasenj¨ ager and Dieter R¨ odding. This heritage determined the focus of B¨ orger’s logical inves- gations in what nowadaysis called computability and computationalcomplexity theory and his early interest in applying methods from logic to solve problems in computer science.