In the emerging deregulated multi-provider telecommunications market place, telecommunications service engineering, enhanced with the architectural framework of the Telecommunications Information Networking Architecture Consortium (TINA-C), promises to pave the way towards an open integrated broadband service infrastructure. In order to be able to populate this infrastructure with a variety of new (sophisticated) telecommunications services, it is necessary to assist and constrain service designers during the complex process of service creation. Therefore, in this paper, after considering briefly a number of service modeling issues, a TINA-C conformant service creation methodology, based on the exploitation of the flexible Unified Modeling Language (UML) notation, is proposed. This methodology is then presented focusing on the role and purpose of essential artifacts, examining their dependencies and illustrating the significance of UML.