The middle ware architecture of the subjectmediators for problemsolving over a set of integrated heterogeneous distributed information resources in the hybrid grid-infrastructure of virtual observatories

The middleware architecture of subject mediators for scientific problem solving over a set of heterogeneous distributed information resources in the hybrid grid-infrastructure of virtual observatory (VO) is considered. The VO hybrid architecture is implemented as a binding of the AstroGrid VO system developed in the U.K. and of the facilities supporting subject mediators developed at the Institute of Informatics Problems of the Russian Academy of Sciences. An approach is implemented according to which for a class of applications, a specification of subject domain is formed independently of preexisting information resources. The hybrid architecture is implemented as the binding of execution engines of two infrastructures (AstroGrid and subject mediators). That is why, in the paper, the main attention is drawn to the problems of rewriting the mediator queries into the plans of their implementation over specific information resources, to the brief description of the hybrid architecture of execution engines of the AstroGrid and subject mediators. An example of implementation in the hybrid architecture of a subject mediator for solving distant galaxies discovery problem is revealed. The distinguishing features of the presented approach comparing to the well-known prototypes of database integration in VOs are overviewed. The middleware architecture of subject mediators is planned to be used for solving the Russian VO problems.