Emerging web services technologies provide an open infrastructure for automated business interaction, thereby creating new opportunities for business actors to collaborate within a networked constellation of enterprises via the Internet. The basis for a viable network of web services (the supporting information system of such a networked constellation of enterprises) is a value model that shows sound value propositions to all actors involved. Requirements engineering techniques can be developed to support: (1) exploring alternative business models, and (2) evaluating alternatives on their economic viability, leading into the design and implementation of technical systems. In this paper we present a Business-oriented Approach Supporting web Services Idea Exploration (BASSIE), which exploits the synergy between the agent- and goal-oriented i* framework and the value-based e3value framework. The approach iterates between exploration of structural alternatives and qualitative evaluation using i, and quantitative modeling and evaluation of business value using e3value. The approach is illustrated with a real-life case study in digital music distribution.