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+$Id: multidb,v 1.1 2006-01-17 11:10:30 mike Exp $
+
+
+YP2 Virtual Databases and Multicast Searching
+=============================================
+
+Two of YP2's filters are concerned with multiple-database operations.
+Of these, "virt_db" can work alone to control the routing of searches
+to one of a number of servers, while "multi" can work with the output
+of "virt_db" to perform multicast searching, merging the results into
+a unified result-set.  The interaction between these two filters is
+necessarily complex, reflecting the real complexity of multicast
+searching in a protocol such as Z39.50 that separates initialisation
+from searching, with the database to search known only during the
+latter operation.
+
+### Much, much more to say!
+