Enhancing WS-BPEL Dynamic Invariant Generation Using XML Schema and XPath Information

The OASIS WS-BPEL 2.0 standard language for Web Service composition eases the creation of advanced services based on others. However, its dynamic and asynchronous nature presents a challenge for traditional white-box testing techniques. Takuan is a tool that can help with this problem. It analyses execution logs of a WS-BPEL process in a real-world WS-BPEL engine to dynamically generate composition invariants. Nevertheless, it suffered some performance issues when handling a large number of variables with complex multidimensional content. In this work, we present two techniques implemented to automatically alleviate these issues. First, we dynamically analyse XPath expressions so only sensible invariants are checked. And secondly, we have extended the Daikon dynamic invariant generator used internally in Takuan to accept XML Schema restrictions which must not be inferred as invariants. We present practical results supporting our work and comment the impact and applicability of these techniques beyond WS-BPEL itself.