Maybe I’m wrong, but as I know No-SQL doesn’t have a good performance like SQL (but for sure maybe a mixed approach SQL + No-SQL be good, maybe)
It seems that Esri uses a relational approach and this document explains relationships, especially “Relationship Class - Navigation Property” which I think would be useful
http://resources.esri.com/help/9.3/arcgisengine/dotnet/2e097482-4f99-4224-896e-8027e6ab883e.htm