Database integration and query optimization in multi-database systems
Hai-Yann Hwang · 1982
Independent database systems may model objects and relationships differently; and may contain mutually inconsistent data. In order to logically integrate them, the concept of generalization is extended to the Functional Data Model, and a versatile view definition facility is provided to resolve inconsistencies. The query modification algorithm for the extended model is given. The query optimization problem in the integrated system is also explored. For queries containing projection or selection, linear-time algorithms are proposed to construct minimum communication-cost strategies to process the queries. The correctness of the algorithms is proved. Algorithms are also proposed to construct efficient strategies to process queries containing join. The processing of general queries is also considered.