Querying Geographically Dispersed, Heterogeneous Data Stores: The PPerfXchange Approach

Syntax Tree Resulting XML Document Process Instructions PPerfXchange Virtual XML Documents Figure 5: An Architectural Overview of PPerfXchange Shown is an overview of PPerfXchange’s architecture. An XQuery is sent to the remote site where it is received by PPerfXchange’s network interface. The query is then parsed, creating an abstract syntax tree (AST). The AST is transformed into a series of process instructions that create a resulting XML document by retrieving data from a set of virtual XML documents.