In large-scale distributed systems the selection of services and data sources to respond to a given request is a crucial task. Non-functional or Quality of Service (QoS) attributes need to be considered when there are several candidate services with identical functionality. Before applying any service selection optimization strategy, the system has to be analyzed in terms of QoS metrics, comparable to the statistics needed by a database query optimizer. This paper presents a classification approach for QoS attributes of system components, from which aggregation functions for composite services are derived. The applicability and usefulness of the approach is shown in a distributed system from a High-Energy Physics experiment posing a complex service selection challenge.

Top