Affiliations: Izmir Institute of Technology, Urla, Izmir, Turkey.
Tel.: +90 232 750 65 32; Fax: +90 232 750 65 05; E-mail:
firstname.lastname@example.org | Institut de Recherche en Informatique de Toulouse
IRIT, Universitè Paul Sabatier, 118, Route de Narbonne, 31062 Toulouse
Cedex, France. Tel.: +33 (0) 5 61 55 82 48 6325; Fax: +33 (0) 5 61 55 62 58;
Abstract: We consider the problem of query execution when there is limited
access to the relations, i.e. when binding patterns require values to be
specified in order to get data from the relation. This problem is common in
virtual data integration systems where there are heterogeneous sources with
various restricted access patterns and query capabilities. Another problem is
the lack of the statistical information about the sources and occurrence of
unpredictable events. We introduce two mobile join operators, MDJoin and
SMDJoin which are designed for restricted sources and implemented using 'mobile
agents' in order to benefit from their autonomous and reactive characteristics.
Mobile operators of restricted sources are capable to deal with restricted
sources and react to the variations between the compile-time estimations and
run-time computations of data during query execution. The difference between
the two new query operators lies in their level of adaptation ability to the
execution environment. Performance results show that mobile agent-based
approach at operator level can lead to a significant reduction in response time
with restricted sources.
Keywords: Virtual data integration, restricted sources, adaptive query execution, mobile agents, mobile dependent join operators, performance evaluation