The dbs interacts with a client - one per connected workspace. The dbs has the same lifetime as the client. The central data structure of this layer is what we call the reference structure , see section 3 . It provides the interface to the editing of the reference structure and via that, the information components. The WWW front end is also built on top of the third layer.
Versions represent the actual appearances of objects at certain times.
The history structure nodes contain object information and historical information of the objects. Attributes are single valued and describe the object's properties, and a number of links which describe the object's relationships to other objects. Past versions of objects can be accessed and reactivated. The temporal history of an object is an order between the different versions of that object and reflects the order of the versions' creation time. We allow several users to take out an object at the same logical time and to create new versions of that object.