Update 01-introduction.md

documentation/design/01-introduction.md

@@ -20,6 +20,14 @@ Some unsorted thoughts the be ordered yet:
 * core of controller should be kept simple/lean, i.e., just the basic primitives
 * core should be extended by modules to add functionality beyond basics
 * modules should be loaded (or unloaded) during runtime of the controller core
+* reuse existing software if possible and if those are stable, i.e., documented, maintained etc,  on a long time
 
 
 ## Structure of this Memo
+
+## Use Cases to be considered
+
+The development of a general purpose SDN controller is not the primary goal at this early stage of the project.
+Instead there are two use cases to be considered in the implemenation works that are currently ongoing:
+* Primary: optical domain SDN-controller for the CoCSN project
+* Secondary: SDN-controller for our local labs to manage an Ethernet-based lab environment