Ph.D. Dissertation Defense - Jinchuan Xia

Date: 27 Jun, 2008
Time: 10:00 AM
Location: 223 Atanasoff Hall
Topic: WS-Pro: A Petri Net based Performance-driven Service Composition Framework
Major Professor(s): Carl K. Chang


Abstract:

As an emerging area gaining prevalence in the industry, Web Services was established to satisfy the needs for better flexibility and higher reliability in web applications. However, due to the lack of reliable frameworks and difficulties in constructing versatile service composition platforms, web developers encountered major obstacles in large-scale deployment of web services. Meanwhile, performance has been one of the major concerns and a largely unexplored area in Web Services research. It is in high demand for researchers to conceive and develop feasible solutions to design, monitor, and deploy web services systems that can adapt to failures, especially performance failures. Though many techniques have been proposed to attack this problem, none of them can offer a comprehensive solution to overcome the difficulties challenging practitioners.

Central to the performance-engineering studies, performance analysis and performance adaptation are of paramount importance to the success of a software project. The industry learned through many hard lessons the significance of well founded and well executed performance engineering plans. The important fact is: it is too expensive to tackle performance evaluation, mostly through performance testing, after the software is developed. This is especially true in recent decades when software complexity rises sharply. After the system is deployed, performance adaptation is essential to maintaining and improving software system reliability. It provides techniques to mitigate the consequence of performance failure and therefore becomes an important research issue. Performance adaptation is particularly meaningful is important for mission-critical software systems and software systems with inevitable frequent performance failure, such as Web Services.

This dissertation focuses on Web Services framework and proposes a performance-driven service composition scheme, called WS-Pro, to support both performance analysis and performance adaptation. A formalism of transformation from WS-BPEL to Petri net is first defined to enable the analysis of system properties and facilitate quality prediction. A state-transition based proof is presented to show that the transformed Petri net model correctly simulates the behavior of the WS-BPEL process. The generated Petri net model was augmented using performance data supplied by both historical data and runtime data. Results of executing the Petri nets suggest that optimal composition plans can be achieved based on the proposed method.

The performance of service composition procedure is an important research issue which has not been sufficiently treated by researchers. However, such an issue is imminent to dynamic service composition where re-planning must be done in a timely manner. In order to improve the performance of service composition procedure and enhance performance adaptation, this dissertation presents a novel unfolding algorithm so that a large portion of the computation time of service composition can be moved to a pre-processing unit; hence the response time is much shortened during runtime. We also extended the WS-Pro to the ubiquitous computing area to improve fault-tolerance.