The editor is also a real-time groupware application. Several people can view and manipulate the concept map at the same time, and any change made by any user is immediately updated on all workstations. Every person's display shows the focal points of all participants, although at lower magnification than their own focus. This multiple focal point display has several advantages in groupware. Our development and use of this interactive fisheye editor for groupware has raised a number of design and usability issues.
People organize concept maps through spatial relationships.
They may, for example, cluster nodes together or line them up in ways that imply meaning in the task domain. Unfortunately, these relationships are difficult to construct in a fisheye space. Similarly, changing a focal point distorts each node differently, which can upset how an existing spatial organization is perceived. Consequently, a user may be forced to adjust node positions every time they change the focus, if they want to keep the visual relationships intact. This can be problematic, since this single node can overlap and occlude other nodes when the map is dense.