1. A method for managing state data of a service in a service-oriented architecture by establishing a pluggable meta-data processor comprising: establishing a platform independent, extensible meta-data information model to define meta-data about the state data of the service; establishing an extensible meta-data definition comprising an extensible set of attributes of the state data of the service, so as to enable the service to extend its state with change notification semantics; configuring one or more extensible semantic processors for interpreting the semantics of a state change query created and sent by a requesting client directly to the service, wherein query language and the one or more semantic processors are each chosen by the client, and which state change query is forwarded from the service to a client-chosen semantic processor; configuring a controller meta-data processor; and defining contracts among said semantic processors.