Companies often need to share an internal database in distant offices, but high running cost is usually the main obstacle for its implementation.

IF Computer Japan has developed IFNET, a managing system for distributed databases on the telephone. This system always keeps the contents of several databases identical. It restrains at the same time the running cost because it only exchanges revised data, and not the entire database.

IFNET administrates the database in three phases: revise phase, transmission phase and conjunction phase. In the first phase, the local database is revised. In the second transmission phase, the data which are identified as reivised ones in the first phase in the local terminals are exchanged and in the third conjunction phase the exchanged data is fed. The change is performed in the file base. Considering the case that files with the same name are revised in both databases between a connection and the next time, the priority of either data- base should be preset or the conflict should be solved manually each time.

IFNET is operated between IF Computer Japan and IF Computer Asia in Hong Kong everyday. Data are exchanged once a day in the midnight. In the future IF Computers all over the world are planned to connect through IFNET and exchange information.

Hardware: UNIX Workstation

Software: IF/Prolog, UNIX