|
Abstract : |
IRO-DB is an object-oriented federated database system to access multiple data sources from an ODMG compliant C++ interface. The system encompasses several components, including local database adapters to homogenize local data sources, a remote object access component to query and transfer collections of objects from site to site, and a mediator to define integrated views, decompose and optimize queries, and combine results. This paper gives an overview of the IRO-DB architecture and describes in detail the cost evaluator currently under elaboration for the next version of the distributed query optimizer. The cost model is composed of a set of mathematical formulas with coefficients to estimate the cost of the search operators. The coefficients are deduced from a calibrating objectoriented database composed of linked collections of objects. A tuning application is run on each local site to adjust the cost formulas and fix the coefficients. We report on the tuning of O2 and ObjectStore. We show that the estimation is quite accurate for path traversals with the OO7 benchmark on top of, |
