System and method of joining data obtained from horizontally and vertically partitioned heterogeneous data stores using string-based location transparent search expressions

Abstract

Described are a system and method for accepting a string-based search expression, parsing the search expression into an expression tree, distributing the tree (or portion thereof) across heterogeneous repositories, and merging the results. The system is data-location transparent, encapsulates a federation model within query nodes and query trees. A client application produces and issues the search expression to the system. One type of expression tree node is an attribute node corresponding to an attribute included in the search expression. Metadata is associated with the attribute node for identifying each repository that supports the attribute represented by that attribute node. A call passes to the expression tree to perform the search, which occurs in a recursive-descent traversal of the tree. The search completes in a single tree traversal. Sub-trees receive a relevant portion of the search expression to translate into a query expression specific for each type of searched repository.