Update 05-implementation.md

documentation/design/05-implementation.md

@@ -25,4 +25,10 @@ The RESTCONF  client stubs used by goSDN are generated from YANG files using YGO
 
 ### Dependencies
 
-For now we can only use the OpenAPI 2.0 standard. This is because `go-swagger` does not support OpenAPI 3.0 specifications yet.
+For now we can only use the OpenAPI 2.0 standard. This is because `go-swagger` does not support OpenAPI 3.0 specifications yet.
\ No newline at end of file
+
+## Storing Information
+
+There seem to be two classes of information to be stored in the controller:
+* short-living information, such as, current topology 
+* long-time information, such as, information about principle network domains, elements in such a domain, etc