Computer systems keep growing in complexity, processing power and web connectivity. To leverage this rich environment and to 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 and engineering related fields. We believe that providing a unified tool and a set of associated methodologies to create end-to-end 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 create an intelligent assistant to help mobile users retrieve online information using a multimodal dialog approach.