On Ruspini's Models of Similarity-Based Approximate Reasoning

In his 1991 seminal paper, Enrique H. Ruspini proposed a similarity-based semantics for fuzzy sets and approximate reasoning which has been extensively used by many other authors in various con- texts. This brief note, which is our humble contribution to honor Ruspini¿s great legacy, describes some of the main developments in the field of logic that essentially rely on his ideas