Managing the Evolution of Mediation Queries

Previous works in data integration can be classified according to the approach used to define objects at the mediation level. One of these approaches is called global-as-view (GAV) and requires that each object is expressed as a view (a mediation query) on the data sources. One important limit of this approach is the management of the evolutions in the system. Indeed, each time a change occurs at the source schema level, all the queries defining the mediation objects have to be reconsidered and possibly redefined. In this paper, we propose an approach to cope with the evolution of mediation queries. Our claim is that if the definition of mediation queries in a GAV context follows a well-defined methodology, handling the evolution of the system becomes easier. These evolution problems are considered in the context of a methodology we have previously defined for generating mediation queries. Our solution is based on the concept of relevant relations on which propagation rules have been defined.