Granularity Metrics for IT Services

Many articles discuss the design of fineor coarse-grained IT services without defining what granularity exactly means. However, this is important to know since the granularity influence e.g. the reusability or the composition effort of services and thus the development, maintenance and composition costs of a service realization. Therefore, we present different metrics to evaluate and compare the granularity of various service realizations of a process where each metric represents a different perspective on service granularity. In addition, we discuss the advantages and disadvantages of these metrics and argue that a reasonable measurement of service granularity can usually be obtained by the combination of the metrics. Furthermore, we illustrate that the proposed metrics may constitute a first step towards the evaluation of the total costs of various service realizations. The application of the metrics as well as the discussion of the practical benefits is illustrated by a real world case.