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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

Department of Computing Science, Faculty of Science and Technology

Research area

Computing science

Project description

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.