Date Added: Sep 2009
The standard database mechanisms for concurrency control, which include transactions and locking protocols, do not provide the support needed for updating complex geographic data in a multiuser environment. The preferred method to resolve conflicts in GIS systems is to encapsulate the modifications generated by the end users through the use of multiple versions. Multiuser (or versioned) geographic databases allow users to operate as though they have full access to the entire dataset. Instead of relying upon row locking, versioned databases allow multiple users to simultaneously edit the same row. They implement a model for conflict detection and resolution where the first to commit the change wins by default (though clients can manually intervene and select the latter change as the winner).