An efficient query evaluation in a mediator based on implementation plan

A labeled-tree approach to semantic and structural data interoperability applied in hydrology domain

“…Currently, there are two commonly used approaches for such information integration:''data warehousing" (e.g., [20,[22][23][24]29]), and ''virtual information integration" (e.g., [6,18,31]). Data-warehouse techniques require importing data from various data sources and maintaining them at a centralized data warehouse; such methods thus provide for centralized control over the data stored within and necessitate that queries are executed at the data warehouse itself.…”

“…Such data integration systems attempt to enable data retrieval from existing heterogeneous and autonomous data sources with a unified query interface, which is significantly different from the data warehouse method. A majority of systems (e.g., [11,12,17,8,35,27,2,26,18]) using this approach emphasize the need for querying capabilities that can pinpoint the most appropriate datasets with a semantically rich query, although, a partially materialized method could also be implemented in mediator to speed up some more frequently used queries (e.g., [21,23]). …”

Efficient approaches for materialized views selection in a data warehouse

“…Materialized views are extremely useful in query optimization [11]. Rewriting a query based on the use of a set of materialized views can yield a much more efficient query execution plan for OLAP query in the DW environment [4].…”