Delivering services cost-effectively benefits from economies of scale, not dissimilar to the production of goods. Customizing services to the specific needs of a customer - either the service interfaces or the delivery system - incurs additional costs of setting up the service delivery system to be able to fulfill a specific variant and the excess costs of operating this additional system. Service providers need to understand the trade-off between service standardization and customization. We propose a domain independent approach to identify the variation scope of existing instances and derive a normative model of admissible configurations. © 2012 IEEE.