Bill O'Farrell

Runtime Monitoring of Web Service Conversations

For a system of distributed processes, correctness can be ensured by (statically) checking whether their composition satisfies properties of interest. However, Web services are distributed processes that dynamically discover properties of other Web services. Since the overall system may not be available statically and since each business process is supposed to be relatively simple, we propose to use runtime monitoring of conversations between partners as a means of checking behavioral correctness of the entire Web service system. Specifically, we identify a subset of UML 2.0 sequence diagrams as a property specification language and show that it is sufficiently expressive for capturing safety and liveness properties. By transforming these diagrams to automata, we enable conformance checking of finite execution traces against the specification. We show how our language can be used to specify the specification property system (SPS). We describe an implementation of our approach as part of an industrial system. Finally, we discuss our experience of specifying and monitoring a number of properties from three existing applications.

Runtime monitoring of web service conversations

For a system of distributed processes, correctness can be ensured by (statically) checking whether their composition satisfies properties of interest. In contrast, Web services are being designed so that each partner discovers properties of others dynamically, through a published interface. Since the overall system may not be available statically and since each business process is supposed to be relatively simple, we propose to use runtime monitoring of conversations between partners as a means of checking behavioural correctness of the entire web service system. Specifically, we identify a subset of UML 2.0 Sequence Diagrams as a property specification language and show that it is sufficiently expressive for capturing safety and liveness properties. By transforming these diagrams to automata, we enable conformance checking of finite execution traces against the specification. We describe an implementation of our approach as part of an industrial system and report on preliminary experience.

Property Patterns for Runtime Monitoring of Web Service Conversations

For a system of distributed processes, correctness can be ensured by statically checking whether their composition satisfies the properties of interest. However, web services are distributed processes that dynamically discover properties of other web services. Since the overall system may not be available statically and since each business process is supposed to be relatively simple, we propose to use runtime monitoring of conversations between partners as a means of checking behavioral correctness of the entire web service system. Specifically, we identify a subset of UML 2.0 Sequence Diagrams (SD) as a property specification language. We show how our language can be used to specify the patterns in the Specification Property System (SPS) [1]. By formalizing this subset using automata, we can check finite execution traces of web services against various complex properties. Finally, we discuss our experience using our language for runtime monitoring of an existing application, and conclude with a description of existing tool support.

A Framework for Verifying SLA Compliance in Composed Services

Service level agreements (SLAs) impose many non-functional requirements on services. Business analysts specify and check these requirements in business process models using tools such as IBM WebSphere Business Modeler. System integrators on the other hand use service composition tools such as IBM WebSphere Integration Developer to create service composition models, which specify the integration of services. However, system integrators rarely verify SLA compliance in their proposed composition designs. Instead, SLA compliance is verified after the composed services are deployed in the field. To improve the quality of the composed services, we propose a framework to verify SLA compliance in composed services at design time. The framework re-uses information in business process models to simulate services and verify the non-functional requirements before the service deployment. To demonstrate our framework, we built a prototype using an industrial process simulation engine from IBM WebSphere Business Modeler and integrate it into an industrial service composition tool. Through a case study, we demonstrate that our framework and the prototype assist system integrators in composing services while considering the non-functional requirements.

XPlainer: An XPath Debugging Framework

XML is an important practical paradigm in information technology and has a broad range of applications. How to access and retrieve the XML data is crucial to these applications. There are two standard ways for accessing and manipulating XML data, the Simple API for XML (SAX) and the Document Object Model (DOM). However, when an application needs to traverse through XML data, it is not easy to retrieve the required data with these two standard ways. XML data is impossible to be retrieved back and forth by SAX, and the graph-oriented DOM notation is not easy to work with. With such limitation, the W3C supervises the development of three important languages: XPath [3], XQuery and XSLT for exploring and querying XML. Among these three languages, XPath is the key and cornerstone language for the other two. XPath defines expressions for traversing an XML document and specifies the set of nodes (XPath 1.0) or the sequence of nodes (XPath 2.0) in the XML document.