Rigorous Methods for Software Construction and Analysis Essays Dedicated to Egon Börger on the Occasion of His 60th Birthday

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."