These user preferences form part of the source rule and can include any aspect of the user environment or link ranking. Users can filter out irrelevant links, also private links can be created that other users do not see. The nonlinearity of information access is not in itself the key feature of hypermedia. Many recent improvements on hypermedia systems involve either making some aspect of the information retrieval or presentation into a user-configurable element, or permitting the user to create personal workspaces within a larger information system. Many of these developments in hypermedia systems reflect the transfer of control from the corporate bodies to the individual users.
Hypermedia is characterised by the ability to change the retrieval and presentation of information.
This characteristic is maximised by the concept of distributed control of information presentation and retrieval. Acknowledgments I wish to thank Eric Youle of DSTO for his valuable comments, and for long discussions on this work. Janet Verbyla has also provided useful comments and is my valued collaborator in this work. Then the famous Fermat's Last Theorem would not have been the mystery that it has for the last few centuries.