Context-aware applications: from the laboratory to the marketplace

Current hardware developments are making mobile computing increasingly attractive. An important class of mobile applications are context-aware applications: applications that change their behaviour according to the user's present context-their location, who they are with, what the time of day is, and so on. This article is about software design for context-aware applications. Currently most such applications have been crafted by experts in research laboratories. Our aim is to factor out a simple class of context-aware applications and make the creation of these as easy as, say, creating Web pages.