The notion of service is becoming increasingly popular as a means for implementing large-scale distributed, reactive systems. Systematic development approaches and modeling notations for services are sill largely missing from the literature. We introduce an Architecture Definition Language for service-oriented software architectures. It provides modeling elements for interaction patterns defining services, as well as for mapping sets of services to target component configurations. We also present a comprehensive software development process that considers services as first class modeling elements. By decoupling the modeling of services from their implementation on target component configurations this process enables exploration of multiple architectures implementing the same set of services. We substantiate our view of services as cross-cutting architectural aspects by providing a mapping from services to aspects in AspectJ. We illustrate applicability of our approach by modeling service-oriented architectures for portions of the Center TRACON Automation System as a running example.