Analyzing Fault-Impact Region of Composite Service for Supporting Fault Handling Process Azlan Ismail *§ , Jun Yan * and Jun Shen * * School of Information Systems and Technology, University of Wollongong, NSW, 2522, Australia Email: {ai423, jyan, jshen}@uow.edu.au § Faculty of Computer and Mathematical Sciences, Universiti Teknologi MARA (UiTM), Selangor, 40450, Malaysia. Abstract—A fault situation occurs to a service needs to be well analyzed and handled in order to ensure the reliability of composite service. The analysis can be driven by understanding the impact caused by the faulty service on the other services as well as the entire composition. Existing works have given less attention to this issue, in particular, the temporal impact situation caused by the fault. Thus, we propose an approach to analyzing the temporal impact and generating the impact region. The region can be utilized by the handling mechanism to prioritize the services to be repaired. The approach begins by estimating the updated temporal behavior of the composite service after the fault situation occurs, followed by identifying the potential candidates of the impact region. The concept of temporal negative impact is introduced to support the identification activity. Intuitively, the approach can assist in reducing the number of service changes in handling the fault situation. Keywords-Faults; Impact Analysis; Temporal Properties; Temporal Impact; Temporal Consistency; Temporal Satisfac- tion I. I NTRODUCTION Service oriented computing (SOC) is an emerging para- digm that provides the fundamental principle in managing and maintaining service-oriented system [10]. A service- oriented system is a group of applications that interact with other(s) by providing and/or consuming services. The combination of these services forms a composite service that is meant to achieve the system’s goal. In the Web service technology, the composite services can be specified using the Web service composition framework, WS-BPEL [16]. From the service consumer perspective, it is important that each service in the composition behaves as required in order to meet the system’s goal. To facilitate the observation of each service as well as the entire composition, a contract can be governed between the service consumer and the service provider which is known as a Service Level Agreements (SLA). In this document, the service consumer defines its requirements on the service. Meanwhile, the service provider justifies its capabilities on the service. The capabilities are specified based on several aspects including QoS metrics. Based on the mutual understanding of both sides, the service is accepted and delivered. In the Web service technology, the SLA document can be specified using the SLA frameworks e.g., WS-Agreement [17]. However, as a software system, the run-time lifecycle of each service is exposed to several kinds of exceptional situations due to various reasons [15] e.g., resource failure and constraints violation. As pointed in [21], the exceptions are the symptom of a failed situation. When an exception is triggered, one of the important tasks is to perform the diagnosis task. This task is meant to determine which services are responsible for the exception. This task may result in a conclusion of a single faulty service or multiple faulty services. When a service becomes faulty, there is a huge risk that the specified temporal requirements cannot be met and the present temporal constraints are violated. The temporal issue is a challenging scenario since we cannot repair the time that has passed. What is needed is to compensate the time of the future activities. Conceptually, the future services(unexecuted services) are the right candidates to support the repair process [22] [5]. There are several repair strategies that can be implemented e.g., replacement, recom- position, or renegotiation. However, if the number of future services are large, the main question here is which services need to be considered for the repair? rather considering all of them. Intuitively, the number of services to be repaired can be significantly reduced by performing the impact analysis. An impact analysis is a process of identifying the potential consequences of a change, and estimating what needs to be modified to accomplish that change [18]. The changes can be classified from multiple perspectives. In the service oriented environment, the evolutionary changes which in- volve the changes for reengineering and improvement have been gaining attentions [12] [11]. However, a fault occurs unintentionally. Thus, it can be classified as an unintentional change or abnormal change. The impact analysis acts as a partitioning mechanism