| The diff utility is an important basic tool, providing a foundation for many of the fundamental practices of software development, such as source code management. While there are many file differencing tools for textual programming languages, including some that look at more than simple textual variations, there are few for visual programming languages. We present an algorithm for comparing programs in structured visual dataflow languages; that is, languages in which dataflow diagrams are embedded in control structures. Using either subgraph or maximum common subgraph isomorphism for matching dataflow diagrams, our algorithm compares programs to determine whether they are semantically equivalent, and if not, to discover the differences between them. We use the visual language Prograph for illustration; however, the mechanism we are proposing could be applied to any controlled dataflow language, such as LabVIEW. |
