BỐI CẢNH vật dụng GUI widget ẩn các chi tiết cụ thể của các thiết bị đầu vào được sử dụng từ các lập trình ứng dụng (cho phép thay đổi có tác động tối thiểu trên các ứng dụng), quản lý tương tác để cung cấp các ứng dụng với kết quả của những hành động của người sử dụng có liên quan, | 268 ANIND K. DEY AND GREGORY D. ABOWD . CONTEXT WIDGETS GUI widgets hide the specifics of the input devices being used from the application programmer allowing changes with minimal impact on applications manage interaction to provide applications with relevant results of user actions and provide reusable building blocks. Similarly context widgets provide the following benefits They provide a separation of concerns by hiding the complexity of the actual sensors used from the application. Whether the location of a user is sensed using Active Badges floor sensors an RF radio frequency based indoor positioning system or a combination of these they should not impact the application. They abstract context information to suit the expected needs of applications. A widget that tracks the location of a user within a building or a city notifies the application only when the user moves from one room to another or from one street corner to another and doesn t report less significant moves to the application. Widgets provide abstracted information that we expect applications to need the most frequently. They provide reusable and customizable building blocks of context sensing. A widget that tracks the location of a user can be used by a variety of applications from tour guides to car navigation to office awareness systems. Furthermore context widgets can be tailored and combined in ways similar to GUI widgets. For example a meeting sensing widget can be build on top of a presence sensing widget. From the application s perspective context widgets encapsulate context information and provide methods to access it in a way very similar to a GUI widget. Context widgets provide callbacks to notify applications of significant context changes and attributes that can be queried or polled by applications. As mentioned earlier context widgets differ from GUI widgets in that they live much longer they execute independently from individual applications they can be used by multiple .
