We propose a domain-specific service selection mechanism and system implementation to address the issue of runtime adaptation of composite services that implement mission-critical business processes. To this end, we leverage quality of service (QoS) as a means to specify rigid dependability requirements. QoS does not include only common attributes such as availability or response time but also attributes specific to certain business domains and processes. Therefore, we combine both domain-agnostic and domain-specific QoS attributes in an adaptive QoS model. For specifying the service selection strategy, we propose a domain-specific language called VieDASSL to specify so-called selectors. This language can be used to specify selector implementations based on the available QoS attributes. Both the QoS model implementation and the selectors can be adapted at runtime to deal with changing business and QoS requirements. Our approach is implemented on top of an existing WS-BPEL engine. We demonstrate its feasibility by implementing a case study from the telecommunication domain.

Web service processes currently lack monitoring and dynamic (runtime) adaptation mechanisms. In highly dynamic processes, services frequently need to be exchanged due to a variety of reasons. In this paper we present VieDAME, a system which allows monitoring of BPEL processes according to Quality of Service (QoS) attributes and replacement of existing partner services based on various (pluggable) replacement strategies. The chosen replacement services can be syntactically or semantically equivalent to the BPEL interface. Services can be automatically replaced during runtime without any downtime of the overall system. We implemented our solution with an aspect-oriented approach by intercepting SOAP messages and allow services to be exchanged during runtime with little performance penalty costs, as shown in our experiments, thereby making our approach suitable for high-availability BPEL environments.