Currently, Uses Cases are the most widely accepted notation despite their restricted expressiveness and overloaded semantic. Other more sophisticated modeling techniques have been developed independently of any other ones and/or for specific application domains. These techniques often provide broad expressiveness but do not include any scalability or any integration with other approaches. In this work, we present a proposal for requirements modeling that allows the integration of the expressiveness of some of the most relevant approaches in the Requirements Engineering arena. By focusing on the scalability with respect to expressiveness and adaptability to the application domain, we have established some basic guidelines and extension mechanisms that give coherence and semantic precision to our approach.