Service Reliability Theory and Engineering

The concepts and methods of reliability theory and engineering are applied to services. This has not yet been done in a systematic fashion because services are intangible and the primitives and concepts necessary to making the connection of intangibles and the mathematical theory of reliability have not yet been documented. A good example of the confusion this causes comes from the telecommunications services industry, where professionals often confuse “network reliability” with what is really the reliability of the services provided over the network: a phrase that could make sense when correctly applied to tangible engineering systems is applied (without proper preparation) to reliability of an intangible, the services. The purpose of this paper is to clarify the notions of service reliability theory and to describe some mathematical models useful for service reliability engineering. The paper covers primitive terms in the theory, basic concepts, failure modes and failure mechanisms for services, service reliability figures of merit and metrics (including modeling and estimation), and describes some open problems. Many of the illustrative examples are drawn from the author’s experiences in the telecommunications industry. The paper offers a foundation for clear discussion and quantitative statements about the reliability of services, and brings clarity to service planning and development . The value for professionals in the quality sciences and quality engineering is in the systematic extension of reliability engineering concepts and techniques to intangibles, in the provision of a framework and language for quantitative study of service reliability, and in focusing quality attention on service industries, now the major part of the economies of many developed countries.