A Visual Logic Programming Language

It is commonly accepted that non-logicians have difficulty in expressing themselves in first order logic. Part of the visual language community is concerned with providing visual notations (“declarative diagrams”) which use visual cues to make the structuring of logical expressions more intuitive. One of the more successful metaphors used in such languages is that of set inclusion, making use of the graphical intuitions which most of us are taught at school. Existing declarative diagramming languages do not make full use of such set-based intuitions. We present a more uniform use of sets in this form of description, which allows simple, but highly expressive diagrams to be constructed from a small number of primitive components. These diagrams —we claim— provide a good alternative notation for a limited, but useful, subset of FOL and, as we show in this paper, are the basis of a visual logic programming language.