One requirement is that it should always be possible to see who is changing what at any time. In nte we achieve this by placing a labelled graphical icon at the place a change is happening. This is necessary not only because it identifies who is making a change, but also because it is not always very obvious that a change has been made. For example, single character changes are not easy for a user to spot if his attention was focused somewhere else at the time. Thus the appearance of the icon serves to mark for a few seconds the location of a change, the nature of the change, and (because the icons is labelled) who made the change.
In nt, all changes are marked in this way. However, when we started to use nte in group conferences, it became clear that the screen could get very congested, and also that when a block of text was deleted, users often could see that a block of text had been deleted and who deleted it from the eraser icon and who deleted it, but could often not remember which text it was that was deleted. The reason for this was that their attention was elsewhere, and all they could tell was that something had gone. The solution was simple - not only display the eraser icon and its label, but also fade the block away so they can see what is happening as it happens. In practice, this fade need take no longer than a second to remove the sense of surprise that the users were feeling when blocks were deleted.
Next: Block Locking Up: Shared Applications in the Previous: Usability Issues Jon CROWCROFT