A mechanism is provided for storing self-defining data and mapping elements with either a fixed set of allowed structures or types or with the structures and types determined by rules. Recovery is enhanced by the use of backward and forward pointers between data and mapping elements for the data elements...http://www.google.com.hk/patents/US6973556?utm_source=gb-gplus-share專利 US6973556 - Data element including metadata that includes data management information for managing the data element
