A database system consisting of a network database and a relational database. When a modification is made to the network database, update log data about the modification is created by an update log creating portion. An updating portion searches an address table for the storage position of an address...http://www.google.com/patents/US5764978?utm_source=gb-gplus-sharePatent US5764978 - Database system having a hierarchical network database and a corresponding relational database 
