Applying an update method to a set of receivers

Abstract

In the context of object databases, we study the application of an update method to a collection of receivers rather than to a single one. The obvious strategy of applying the update to the receivers one after the other, in some arbitrary order, brings up the problem of order independence. On a very general level, we investigate how update behavior can be analyzed in terms of certain schema annotations, called colorings. We are able to characterize those colorings that always describe order-independent updates. We also consider a more specific model of update methods implemented in the relational algebra. Order-independence of such algebraic methods is undecidable in general, but decidable if the expressions used are positive. Finally, we consider an alternative parallel strategy for set-oriented application of algebraic update methods and compare and relate it to the sequential strategy.