Alain Colmerauer (1941-2017) was a French computer scientist best known as the creator of Prolog, the most influential logic programming language. After early work in Grenoble and a period at the University of Montreal, he led the artificial intelligence group at the University of Aix-Marseille, where Prolog was born.
Colmerauer came to programming languages by way of language itself. In Montreal he developed Q-Systems, a formalism for rewriting trees that was used in machine translation, and his goal in Marseille was to build a tool that could take in concepts described in French and answer questions about them in French. Pursuing that aim with Philippe Roussel and others, the group built a system around a refinement of John Alan Robinson’s resolution principle, and in 1972 that work crystallized into Prolog. Rather than telling the computer how to compute, a Prolog programmer states facts and rules and poses queries, and the system searches for answers. It was, as colleagues put it, a new way of thinking about what a program is.
Colmerauer did not stop with the original language. Through Prolog II, III, and IV he extended logic programming to handle infinite trees, Boolean algebra, and arithmetic over the real numbers, making him one of the founders of constraint logic programming, a powerful approach for problems that mix logic with numeric and combinatorial constraints.
Why business readers should care: the declarative style Colmerauer pioneered, stating what is true and letting the machine derive consequences, runs through database query languages, business-rule systems, and constraint solvers used for scheduling and configuration.