RACCOON: A Peer-Based System for Data Integration and Sharing
ICDE '04 Proceedings of the 20th International Conference on Data Engineering
Distribution and synchronisation of engineering information using active database technology
Advances in Engineering Software - Selected papers from civil-comp 2003 and AlCivil-comp 2003
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To integrate many data ources we use a peer mediator framework where view defined in the peers are logically composed in term of each other. A common approachto execute queries over mediators is to treat views in datasources as 'black boxes'. The mediator locally decompose queries into query fragment and submit them to thedata sources for processing. Another approach, used in distributed DBMSs, is to treat the views as 'transparent boxes'by importing and fully expanding all view and merge themwith the query. The black box approach often leads to inefficient query plans. However, in a peer mediator frameworkfull view expansion (VE) leads to prohibitively long querycompilation times when many peer are involved. It alsolimits peer autonomy since peer must reveal their view definitions. We investigate in a peer mediator framework thetradeoff between none, partial, and full VE in two differentdistributed view composition scenarios. We show that it isoften favorable with respect to query execution and sometimes even with respect to query compilation time to expandthose view having common hidden peer subviews. However, in other cases it is better to use the 'black box' approach, in particular when peer autonomy prohibit viewimportation. Based on this, a hybrid trategy for VE in peermediator is proposed.