Visual Programming Languages

Visual programming languages are an important recent development in computer science. It has been argued that they enable users to understand programs more easily. However, many suffer from the disadvantage of having no properly specified formal semantics which means that proofs of program correctness are virtually impossible.

At the QSR group, Tony Cohn and John Gooday have worked on providing visual languages with a formal semantics via RCC. We have focussed our attention on Pictorial Janus, a visual form of the Janus parallel logic programming language (an example Janus program is shown below). Using continuity networks we were able to give a full account of the procedural semantics of the language and we hope to use this in conjunction with QSSIM, our qualitative simulation program, to simulate the execution of Pictorial Janus Programs. This approach is intended to provide a method for the rapid prototyping of visual languages: if a semantics is specified in our spatial logic then program simulations can quickly be constructed allowing the designer to explore the expressive capabilities of his language directly.