In the days of its foundation, the field of science covered by UNIF – a series of annual international workshops on unification – was still in its infancy. With the advent of automated reasoning, term rewriting, logic programming, natural language processing, and program analysis, the areas of computer science concerned by unification were seething with excitement. With the coming out of researches in constraint solving and admissibility of inference rules and with the breaking out of applications, such as type checking, query answering, and cryptographic protocol analysis, the development of unification was not long in going at full speed.