C How to Build Smart Appliances ?

advertised as smart devices since they have enhanced features beyond basic functionality. However, these devices are often regarded as complex and complicated rather than smart. Our notion of a smart appliance is different; we suggest that smart devices are devices that are not ignorant about their environment and context. From our working definition it can be seen that the understanding of context, context awareness, and the concepts that enable context awareness are central to our work. In order to gain this understanding we will discuss the following issues in more detail in this article: • What is context? How do we relate a certain real-world situation to the more abstract notion of context? • What is behind the idea of capturing information to approximate context? What technologies are available to capture information about the situation? How can context sensing be implemented? • What mechanisms and methods are useful to translate the information about the situation captured to a more abstract concept of context? • How can applications be built to make use of context? How does this help to make human-computer interaction more implicit and therefore more natural? To answer the questions stated above, we first introduce a terminology for context awareness, then talk about sensing the real world and ways for abstractions, leading to an architecture for context-aware devices. Then we introduce a method to build such devices and discuss possible application domains. We then describe a feasibility study in which we developed a smart mobile phone that is aware of the context of usage and activity of the user. This case study was also used to validate our method. Up to the mid-'90s, context-aware devices were a synonym for location-aware devices [1, 2], but context means much more than location [3]. We use the term context in a more general way to describe the environment, situation, state, surroundings , task, and so on. In the Technology for Enabled Awareness (TEA) project [4] we define context awareness as knowledge about the user's and device's state, including surroundings , situation, and location. From our experience we learned that it is important to discriminate between the real-world situation, the data captured to represent the situation, the abstract representation of the situation, and the behavior of the application according to this information. In current literature this discrimination is often not clear. We suggest the following terminology: • Situation or situational context: These …