By relationship you mean the database schema?. You can integrate CW2K with other 3rd party NMS apps like HPOV, NetView etc. Details on the procedure is available in the CW2K docs. As for the db schema, it's not published. However, with RME 3.4, there's a Data Extraction Engine tool on CCO which can be used from CLI to export the RME data in Inventory in XML format.