Viola: A Verifier For Interoperating Components

Two or more components (e.g., objects, modules, or programs) interoperate when they exchange data, such as XML data. Currently, there is no approach that can detect a situation at compile time when one component modifies XML data so that it becomes incompatible for use by other components, delaying discovery of errors to runtime. Our solution, a Verifier for Interoperating cOmponents for finding Logic fAults (Viola) builds abstract programs from the source code of components that exchange XML data. Viola symbolically executes these abstract programs thereby obtaining approximate specifications of the data that would be output by these components. The computed and expected specifications are analyzed to find errors in XML data exchanges between components. We describe our approach, implementation, and give our error checking algorithm. We used Viola on open source and commercial systems and discovered errors that were not detected during their design and testing.