Abstract 1 1 Introduction 2
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- Figure 2: A taxonomy of multiple window coordination (North Shneiderman, 1997)
- Figure 3: Samples of presenting window relations
5.3Presentation LevelMost GUI technology is organized around “windows” as a basic unit. The window is a rectangular area for display that has some degree of automated functionality provided by a window manager program. These include the reporting of various events such as: window events -- exposure, resizing, etc.; user events -- mouse clicks, keyboard actions, etc.; and system events -- OS interrupts, signals, inter application messaging, etc. Window systems allow -- require -- that windows be organized within other windows -- creating a hierarchy. Within X-window terminology, all graphical objects are windows, including icons and scroll bars. From this viewpoint, each navigational tool may be defined as having its own window. The integration of tools is then concerned with the placement of windows and indication of relations among windows. The layout of windows may be static or dynamic. Windows may be laid out side-by-side or overlapped. The advantage of side-by-side windows is that all information is presented in a single view. The disadvantage is that the territory of all the windows must be less than the territory of the display itself. Using overlapping windows, the total territory in all the windows may be many times greater than the amount of display territory. The disadvantage is that some (most) of the total amount of information will be hidden from view at any given time. Interaction can resolve this problem by allowing the user to select which window should be up front. X-Windows provides facility to do an automatic “bring to front” when the mouse enters the window area. MS Windows 95 uses a “task bar” to aid this process. Some applications provide “stay on top” option to avoid occlusion by other windows. Observation data show that cycle thru windows is relatively higher than other related activity with windows (Gaylin, 1986). Many applications which use a multi-windows scheme provide an automatic layout as either tiled or overlapping. Window layout is dependent on the tasks being performed. Tasks that require little window manipulation can be performed faster in tiled than in overlapping windows (Bly & Rosenberg, 1986). Kandogan and Shneiderman (1997) propose an elastic window scheme to address this problem by using hierarchical window organization, multi-window operations, and space-filling tiled layout. North & Shneiderman (1997) provide a taxonomy of multiple windows coordination. It is a two dimensional taxonomy. The first dimension relates to the data in the two windows, which is either the same or different. The same data may be has different presentation in each window. Different data should have explicitly defined relations among them. They may be an aggregate of data items. The second dimension is the nature of the window function. It is suggested that the windows might be either selection or navigation windows. Thus, the second dimension would be:
The navigation action is described as scrolling, zooming, following link, opening file, etc. The six cases of combination are show as Figure 2. Shneiderman and North have reviewed the advantages in presenting data with multiple windows with coordination between them. They implemented a “snap-together visualization” which allows a user to define coordination of windows (North & Shneiderman, 1999). Figure 2: A taxonomy of multiple window coordination (North & Shneiderman, 1997) 
Multiple window techniques may encounter difficulty in presenting relatedness among windows on the screen. Many windows from various applications may be shown on the same screen. As more windows are added, the screen becomes crowded. The windows may be shown to be related by presenting them within a single application window. Relationships among windows may be shown by synchronization of changes. Interactions in one window can be used to change other windows. For instance, when the data from one window is changed by interaction, e.g. selection, the contents of another window, e.g. a contents window, can be changed. The relation may be explicit -- shown by some presentation such as a line and an arrow--or unannounced. Some examples are shown in Figure 3. A pop-up window is a multiple window where a second window appears only after some interaction. A pop-up window also captures control from a main window. A common type of pop-up window becomes active on mouse click action and disappears when some button on the window is clicked. Some variations such as Balloon Help in Apple™ system and Tool Tips in MS windows™ are activated when the mouse pointer has been over some specific area for some specified amount of time. A pop-up window may be kept open via some holding action. A “Pin” is used in the X Windows system to keep a pop-up menu open even after the pointer has left the menu area. The location of a pop-up window varies; positioning at the center of the screen is common practice. Many applications position a pop-up window under the active area to avoid obstruction of the active area. A pop-up window is considered to take a focal of attention from a main window. The second window may be the same size and at the same position as the current window but with a transparency property. Data is drawn on the transparent window which is layered on top of the other window. The data from a new layer may block the view of the layers beneath. This scheme is used when spatial encoding of both views is similar. The interaction of views should be coherent in both layers. The magic lens uses a scheme where a second smaller window is positioned in the larger window, and the contents of the smaller window is a function of location within the main window. Change mode of display may be considered as a second window replacing the first window. In change mode of display, an interaction may be preserved or it may use a new set. Mode changing has the disadvantage of associating information from a previous display with a new one. It requires recognition overhead. Figure 3: Samples of presenting window relations
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