IMPROVING QUALITY OF WEB SERVICES BY USING REPLICATION
Author(s):
Dirk Thißen,
Thomas Brambring
Paper abstract: Web services define a kind of middleware for implementing distributed applications independent of
underlying platforms and used programming languages. In the development of new software systems,
functionality of existing services can be re-used to reduce development time and costs. This process of
re-use can be done by web service composition. But, current web service standards are not equipped to
consider non-functional requirements, i.e. quality of service (QoS) aspects of a user to a service, neither
in the development of single services, nor in composed services. Thus, capabilities of services, especially
of composed services cannot be guaranteed. But, in competition between service providers such
capabilities can be of special importance in attracting customers. This paper presents an approach to
consider QoS aspects of web services by using service replication. When a user needs to select a service
for usage from a service registry, possible candidates are chosen depending on the QoS requirements of a
user to the service. Replication now ensures that the QoS requirements are not only considered at service
selection time, but also can be granted at service runtime. To do so, integrated in the service selection it
is decided if and how a service has to be replicated for fulfilling the user’s requirements. A flexible
replication architecture is developed, supporting different replication strategies to give guarantees for
several user requirements, as well for single services as for composed services.
Keywords:
Web services, replication, quality of service, service composition, proxy
