Date Added: Nov 2011
A major challenge faced by today's information systems is that of evolution as data usage evolves or new data resources become available. Modern organizations sometimes exchange data with one another via declarative mappings among their databases, as in data exchange and collaborative data sharing systems. Such mappings are frequently revised and refined as new data becomes available, new cross-reference tables are created, and corrections are made. A fundamental question is how to handle changes to these mapping definitions, when the organizations each materialize the results of applying the mappings to the available data.