A Study on Consistency in Multi-user GIS

GIS is widely used in many fields. With the rapid development of computer network,GIS users care more about data sharing. In traditional database, data consistency was controlled by consistency control mechartism. When a data object is looked in a sharing mode,other transactions can only read it, but can't update it. This is appropriate in traditional databases which store at tribute data and mainly deal with short transactions. In spatial databases, because of a large amount of data and complex topological relations, long transactions are used frequently. If the tra ditional consistency control method has already been used, the system's concurrency will be badly influenced. So there come many new requirements about the consistency control in the field of GIS.In this paper, data consistency is discussed in multi-user geographical information system.When a user updates some spatial data that have been accessed by other users in database,or exe cutes a UNDO/REDP operation, data consistency probably be destroyed. To solve the problem caused by the first case, a "notification-reread method"is introduced. As for the second case, there are many problems to be studied.