Quality of Service for Workflows and Web Service Processes

Abstract

Workflow management systems (WfMSs) have been used to support various types of business processes for more than a decade now. In workflows for e-commerce and Web-services applications, suppliers and customers define a binding agreement or contract between the two parties, specifying Quality of Service (QoS) items such as products or services to be delivered, deadlines, quality of products, and cost of services. The management of QoS metrics directly impacts the success of organizations participating in e-commerce. Therefore, when services or products are created or managed using workflows, the underlying workflow system must accept the specifications and be able to estimate, monitor, and control the QoS rendered to customers. In this paper, we present a predictive QoS model that makes it possible to compute the quality of service for workflows automatically based on atomic task QoS attributes. To this end, we present a model that specifies QoS and describe an algorithm and a simulation system in order to compute, analyze and monitor workflow QoS metrics.

QoS-aware service composition for cloud manufacturing based on the optimal construction of synergistic elementary service groups

“…The minimum and maximum values of each QoS property of a MCS were firstly found out in respective CMCSSs. And these values were used to compute the absolute minimum/maximum QoS of the manufacturing task T (by using the aggregation patterns and formulas proposed by Cardoso [45]). Let minQ(T) and maxQ(T) denote the absolute minimum/maximum QoS of the manufacturing task T, respectively, and then the QoS requirements of T values can range from minQ(T) to maxQ(T).…”

“…Traditionally, a composite service was plainly composed in a OOM pattern, which contained the following features [44,45]: (1) each component service on the execution path of the composed composite service strictly matches the corresponding one subtask in the workflow of the given task, (2) the execution path has the same topology as the workflow, and (3) each component service is plainly related to an appropriately chosen elementary service (MCS). Although plain composition was widely employed in most cases of QoS-aware service composition, a plainly composed composite service can hardly make rapid improvements of overall QoS and success rate [25].…”

“…In line with the principle of the new approach, several functionally equivalent MCSs can be combined as a whole (SESG) to execute a subtask of a MFMT, which removes the assumption of one-to-one mapping between MCSs and subtasks, so as to enhance the QoS performance and success rate of service composition. For the sake of illustration, typical QoS properties in [45] (i.e., time, cost, and reliability) are used as the criteria to evaluate the QoS of MCSs, SESGs, and MCCS. More properties can also be added without fundamentally altering the model and related algorithm.…”

“…That is because the former (aggregation patterns) expresses the structural relationships between different subtasks or services with different functionalities in a MFMT or MCCS; by contrast, the latter (redundant structures) characterizes the structural properties of several functionally equivalent elementary services (MCSs) within a SESG. The aggregation formulas of those patterns have been studied by Tao et al [22] and Cardoso et al [45] and applied to calculate the QoS of a MCCS composed with elementary services (MCSs). Let in seq , in par , in sel , and in cir denote the instance of sequence, parallel, selective, and circular patterns, respectively.…”

A model-driven method for describing and predicting the reliability of composite services

“…This approach does not consider the component's reliability as an input to the prediction step. In [41] a reliability model is proposed for evaluating both atomic and composite Web services, similarly to the approach proposed in [5]. The authors first propose a reliability model for atomic Web services and then derive the reliability model of the composite Web service by considering both the relationship among the atomic services and the reliability model of each component service.…”