LINCKS provides a basic change notification mechanism. A marker is created in the server when we create the transient version in our workspace. We notify users who retrieve objects having a marker in the database.
: `Another user is already editing' notification
When a user A accesses an object which is being updated by user B, the user A receives a notification (see figure 3) that user B is already editing this object. If user A then starts to modify the object, user B will receive notification that user A have started to modify the object (see figure 4). The case is similar when several users update a certain object simultaneously. The notification consists of a message and visual aid (see figure 5). The objects (or parts of objects in the case of composite objects) which are affected are shaded.
: `Somebody started modifying one of your modified objects' notification
The described implementation of change notification cannot handle the following case. We have several users with the same object (not modified) in their workspaces. One user B modifies the object, but the others users will not receive any change notification until they either change the object themselves or retrieve the object again from the database. This is natural since the modification created a transient version (and thus a marker) and the system does not know which users have retrieved the object.
: Window shading for parallel editing