1. A method for providing a unified user interface to two or more search providers, each adapted to search a different data store and each having one or more unique query operators or query-definition fields, the method comprising: identifying at least the unique query operators and query-definition fields supported by each search provider by receiving information from each search provider identifying its unique query operators and query definition fields; displaying a user interface that allows definition of a query based on one or more of the unique query operators or query-definition fields, the user interface including in query definition input fields the unique query operators and query definition fields identified; and processing the query by passing information regarding the one or more unique query operators and query-definition fields in the query to at least one of the search providers.