1. A method for persistent querying in a federated database system having a plurality of connectable database management system nodes, each database node having at least one database, the method comprising: receiving a query at a first database node; propagating the query from the first database node to other database nodes in the federated database system; receiving, by the first database node, query results sets from at least one responding node, wherein at least one responding node satisfying the query: obtains a query results set; defines a topic identifier for the query; and publishes subsequent messages relating to the topic identifier when data updates are available; and subscribing, by the first database node, to topic identifiers for publications of subsequent messages from the responding database nodes.