Visual Logic Programming by Means of Diagram Transformations

We believe that the pragmatics and understanding of formal logic and also declarative programming languages are sensible to the type of syntax used. Our goal is to study how to apply the new developments in the eld of diagrammatic reasoning to declarative programming languages. In this paper we summarize the work done up to now in a visual logic language developped at the IIIA. We also attempt a complete formalization of its syntax, semantics and inference system. We claim that our visual syntax and operational semantics have a higher degree of homomorphism with respect to the mathematical semantics of the language than in conventional textual languages. Finally, we study two interesting new features: the ability of intuitively keeping track of the proof and the possibility to represent several solutions to the query, both using a single diagram.