Use case:
User is looking at BPEL design view.
The BPEL navigator and the propperty sheet are synchronized so that as user
selects different nodes in the design view, the navigator and property sheet
change accordingly.
User switches from BPEL design view to BPEL source editor.
User moves cursor to a line of code in the source editor
User wishes that the navigator and property sheet would be consistent with the
currently selected BPEL source element.

Scenario
User works in Design view
Navigator and Property sheet respond to selection changes to remain in sync with
Design view selection.
User switches to Source view
Navigator and Property sheet respond by synchronizing their presentation to be
consistent with the current position in the source editor
As user chanage current position in the source editor, the Navigator and
Property sheet track the changing position.
When user swithches back to Design view, the current position in the Design view
is still what it had been when user was last looking at Design view. 
Navigator and Property sheet react by syncing back up with Design view.

In short, Design view and Source views are what are called TopComponents. The
plan is to have Navigator and Property sheet remain in sync with the current
active anode in the current TopComponent.  Today this behavior is only present
for Design view. This feature will extend this functionality to the Source view.