diff --git a/documentation/design/05-implementation.md b/documentation/design/05-implementation.md
index 52b51866f9316161b6a948bcad0b13f6eceb32ee..1f14088149141d457093dc022c806bd9aaf61ac9 100644
--- a/documentation/design/05-implementation.md
+++ b/documentation/design/05-implementation.md
@@ -29,6 +29,20 @@ For now we can only use the OpenAPI 2.0 standard. This is because `go-swagger` d
 
 ## Storing Information
 
+This section keeps by now some loose thoughts about what information has to be stored how and where. 
+
 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 
+* short-living information, such as, current configured network flows or obtained network configuration out of use case #1 (CoCSN)
+* long-time information, such as, information about principle network domains, elements in such a domain if directly learned from SBI, etc 
+
+This may or may not result in two different places to store data. Unclear yet. 
+
+### Some more details for implementation for the database(s)
+
+We define the principle network domain (PND) and each piece of information of any PND has to be stored in relation the particular PND. 
+
+Specification of a PND:
+* Human readable name of PND
+* Textual description for further information
+* Set of supported Southbound-Interfaces, e.g., RESTCONF, TAPI, OpenFlow etc
+* Phyiscal Inventory Network Elements, hosts and links 
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