View Update by Cooperation in Component-Based Database Systems
Research project
In this research, a new way of supporting updates to views is being investigated --- update by cooperation.
Computers are often used to store large amounts of information in database-management systems. The organization of these data is often very complex, rendering it difficult to make changes in a consistent fashion. In this work, a new approach to the support of such changes, which requires the cooperation of all users affected by the changes, is investigated. In comparison to existing methods, this new approach promises to reduce the amount of inconsistency in computer databases.
Project overview
Project period:
2008-01-01 –
2008-12-31
Participating departments and units at Umeå University
Updating a database through a user view, or window, is known to be a difficult problem at best. In general, there are many possible updates to the main schema which map to a single update on the view; the problem is then to decide which of those possible updates on the main schema, if any, is appropriate. The gold standard is the constant-complement strategy, which is precisely the approach which avoids all update anomalies, i.e., changes to the state of the main schema which are not visible in the view. However, the constant-complement strategy is rather conservative with respect to the view updates which it allows, and has therefore been regarded as too restrictive by some. On the other hand, extensions to the constant-complement strategy are in general rather ad hoc, and provide limited extension at best.
Even if one accepts that view update strategies which are more liberal than the constant-complement approach are to be allowed, the further issue of access rights must be addressed. Views are often used to limit access rights. Thus, if a view update is reflected to an update of the main schema which is not entirely visible within the view, it is quite likely that the user of the view does not have the necessary privileges to make such an update, and so it must be disallowed.
In this research, a new way of supporting updates to views is being investigated --- update by cooperation. If a user of a view wishes to perform an update which does not respect the constant-complement strategy (that is, which entails side effects), then that user must enlist the cooperation of users of other views to complete the request. The agreed-upon update on the combined views of these users must respect the constant-complement strategy.
