Managing the Quality of Modular Services -- A Process-Oriented Aggregation of Expected Service Levels Based on Probability Distributions

Service oriented architectures provide modular service components which can be combined to complex services. Besides the problem of finding optimal combinations of service components the quality of the overall service (the complex service) is important. It is often assumed in literature that the quality of the individual service components is expressed as one single value (e.g. the average). In fact, we observe different probabilities for certain quality levels which are summarized in a probability distribution of the service level indicators. Given the distribution of the quality levels of the individual service components we present an approach to aggregate these distribution functions. As such, we are able to derive one distribution function for the overall complex service. The distribution function of the complex service carries much more information than a single value. This fact is essential for analyzing, managing and controlling the overall process in order to detect weaknesses and to approve overall quality.