Computer systems keep growing in complexity, processing power and inter-connectivity. To leverage this rich environment and better assist users, a new type of intelligent assistant software is required. Building intelligent assistants is a difficult task that requires expertise in many AI related fields including natural language interpretation, dialog management, multimodal fusion and brokering of services. We believe that providing a unified tool and a set of associated methodologies to create intelligent software will bring many benefits to this area of research. Our solution, the Active framework, introduces the original concept of Active Ontologies to model and implement intelligent applications in a single and coherent software environment. As an example, this paper illustrates how Active has been used to implement an intelligent assistant to help surgeons in a computer equipped operating room.