Interactivity

As a general rule, constraints on interactivity between users via a shared application should be kept to a minimum, and only imposed as a policy where the users actually require such constraints rather than imposed by the mechanism of the shared application. Thus with a shared editor, the mechanism implementing the editor should allow multiple users to edit the document simultaneously. Thus if the sharing mechanism requires a lock to be imposed on a part of the data set, then this lock should be imposed on as small a part of the data set as possible to maximise the potential interactivity that can be achieved between users through the editor. However, the imposing of locks of any sort is at odds with the resilience/scalability requirements above, and because we do not require global consistency at any time, the use of locks should be avoided if suitable alternative solutions are available.