1. A system which uses a query-network to represent social connections in a social network comprising: a database apparatus of an online social network which is connected to a network and comprises: an interface; and a memory storing code; and a processor coupled to the interface and the memory which executes the code, the code comprising: code instructions for updating a plurality of nodes of a query-network representation of a plurality of social connections between a plurality of participants of a social network by performing the following for each one of said plurality of participants: code instructions for using said interface for communicating with a respective said participant over said network to acquire a policy for establishing social connections between said respective participant and other participants of said plurality of participants; code instructions for specifying an edge-defining query and an edge-accepting rule according to said policy; code instructions for associating said edge-defining query and said edge-accepting rule with one of a plurality of nodes in said query-network representation; code instructions for defining said plurality of social connections by automatically and recursively adding or subtracting a plurality of edges each connecting between a pair of said plurality of nodes until said edge-defining query and said edge-accepting rule of said plurality of nodes are complied with; wherein each one of said plurality of edges represents a social connection that is complied with a respective said edge-accepting rule of one of said plurality of nodes and a respective said edge-defining query of another of said plurality of nodes.