It displays in its central display field a graphic representation of the specific design units contained in a specific state of the design space associated with a problem statement. A command bar allows the designer to trigger the execution of tasks by selecting the appropriate buttons. In the present interface this is used for interactive query, search control and debugging. It remains an open question whether the eventual SEED-Config interface will have such programming access. The visual connections between the four windows are shown in Figure 13 .
Visual connections are only a view onto underlying logical structure.
A state may differ from its successor states in both its problem definition and its design solution. This implies that, within a SEED world, there is no authoritative problem description. In fact the design space structure records changes to the problem description as well as changes to design solutions. Nonetheless, the interface is presented to a user in a hierarchical fashion. A PH window specifies a problem structure.