Abstract
Dynamic selection and dynamic binding and rebinding at runtime are new characters of composite services. The traditional static reliability prediction models are unsuitable to dynamic composite services. A new reliability predicting algorithm for composite services is proposed in this paper. Firstly, a composite service is decomposed into composition unites (executing path, composite module and atomic service) according to their constituents. Consequently, a hierarchical graph of all composite units is constructed. Lastly, a new dynamic reliability prediction algorithm is presented. Comparing with the traditional reliability model, the new dynamic reliability approach is more flexible, which does not recompute reliability for all composite units and only computes the reliability of the effected composite units. In addition, an example to show how to measure the reliability based on our algorithm is designed. The experimental results show our proposed methods can give an accurate estimation of reliability. Furthermore, a more flexible sensitivity analysis is performed to determine which service component has the most significant impact on the improvement of composite service reliability.
Highlights
With the rapid development and widespread use of web services, more and more businesses are achieved by composite services which can be created by aggregating a number of atomic or composite services by following certain composition pattern and rules
A new approach has been proposed to evaluate the reliability of composite services based on the hierarchical graph of composite units
The composite services can be decomposed into four different kinds of composite units, and they are Atomic Service (AS), Basic Composite Module (BCM), Path, and Composite Service (CS) nodes in the hierarchical graph from bottom to top layer
Summary
With the rapid development and widespread use of web services, more and more businesses are achieved by composite services which can be created by aggregating a number of atomic or composite services (called service components) by following certain composition pattern and rules. A large amount of functionequivalent services has been in the Internet, which make more services be selected Users can translate their requirements for services to the constraints of some QoS properties [1]. In local binding, when a composite service is running, one of its service components is bound to a selected service according to some QoS properties before it is invoked. Mathematical Problems in Engineering of some service components do not satisfy the requirements of the user or the bound services fail, the composite service will pause, and after new services are bound to the service components, the composite service continues to run; the binding in this process is called rebinding at runtime. A new dynamic reliability model is presented for the dynamic service composition in this paper.
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