3. Background: Towards an Information Centric User Interface ArchitectureThe VISAGE user interface paradigm takes an aggressively information-centric approach to the presentation of information to the user. The information-centric approach may be thought of as the next logical step along the path from application-centric architectures to the modern document-centric approach. The distinctions among the three approaches hinges on differences in the "basic currency" through which the users interact with the system.In application-centric architectures, the basic currency is the file. The file system is completely exposed to the user and a somewhat detailed understanding of its workings is a prerequisite to the productive use of the system. Moreover, although files in the file system are the basic unit of information, the files themselves are of little use to the user. To access the information in their files, users must rely on "applications" to fetch and display the information from the files on their behalf. In this regard, applications are like remote manipulator arms in nuclear power plants--users are not allowed to "touch" their data, except indirectly via various special-purpose tools. Each application has it's own user interface which defines what kinds of files people can manipulate and what they can do with them. With the introduction of graphical user interfaces and the desktop metaphor, files became concrete visual objects, directly manipulable by the user, storable on the desktop or in folders, and--to a limited extent--arrangeable by users and software in semantically meaningful ways. But the contents of those files were still out of direct reach of the user. The advent of document-centric interface paradigms has introduced many positive changes into this story. In this world, the basic currency is no longer the file but rather the document--an entity with some potential meaning in the user's world-outside-the-computer. The role of the application is subordinated (and perhaps ultimately eliminated) in favor of component architectures whose interactions with the user are focused on direct manipulations of documents. Documents may be kept on the desktop in addition to files and may be directly activated and manipulated via drag-and-drop operations. Documents may serve as containers for other documents, enabling natural modes of grouping and attaching information together in meaningful units. Some extremely document-centric interfaces (e.g. Workscape, [3], Web Forager [5]) permit the spatial arrangement of large numbers of documents, enabling effective visualizations of the relationships among them. The application of dynamic query techniques in a document-centric world enables visual search paradigms. In document-centric interfaces, users can almost literally "get their hands on" their documents. The information-centric approach in Visage simply represents a natural continuation of these trends. Visage abandons the primacy of the document wrapper as the central focus of user interaction in favor of the data element as the basic currency of the interface. Rather than limiting the user to files and documents as targets of direct manipulation, Visage permits direct drag-and-drop manipulation of data at any level of granularity. A numeric entry in a table, selected bars from a bar chart, and a complex presentation graphic are all first-class candidates for user manipulations, and all follow the same "physics" of the interface. The object oriented nature of this approach is clearly is not unique to Visage and indeed was introduced and explored in Smalltalk and other systems (e.g. 10). Our work addressed the user interface issues raised in using this approach throughout an information visualization and exploration environment. |