About Query Expression

This component provides a way to express queries in a generic manner. Its centerpiece is a class called XMLQuery that uses boolean postfix expressions to capture the domain, range, and constraint of a query, regardless of the source of the query (SQL, keyword query, etc.). It can also encapsulate the results of a query. It's used by many other components as the standard way to pass a query and its results between servers, clients, nodes, and other components.