In this paper a holistic approach to automated service composition in Service Oriented Architecture is presented. The model described allows to specify both functional and non-functional requirements for the complex service. In order to do so a decomposition of the complex service composition process into three stages is proposed, in which a structure, a scenario and an execution plan of a complex service is built. It is believed that service composition tool based on the proposed model will be able to create complex services satisfying efficiently both functional and nonfunctional requirements.