1. A system for sharing data objects among applications available on a network, comprising: a data protocol layer that permits a flow of data messages among applications on the network, at least a portion of the data messages including at least one data object; a client library coupled between each respective application and the data protocol layer; a data-type definition language that defines one or more data-types shareable among the applications through each of the respective client libraries; a data-set definition language that defines data-object sets that are of a given data-type; one or more data stores that contain data objects including, singularly or collectively, the data objects in the data-object sets; a data request module associated with each client library and operable to request data objects from the data stores that match a particular data-object set; a management server comprising code performing in a server of the type having a memory and a processor and being in communication with the data stores and configured to receive a request from the data request module, parse the request, and retrieve any matching data objects; a registration module associated with the management server and configured to accept subscriptions from subscribing applications, wherein the subscriptions have a filter criteria in the data-set definition language that match given fields of the data objects; and an event notification module associated with the management server and configured to receive an event message from the applications on the network, compare the at least one data object in the event message with one or more of the subscriptions, and selectively notify only a portion of the subscribing applications in response to the comparison on the basis of any matches of the filter criteria, wherein the event notification module is operable to identify whether the event message indication is an in-scope, an out-of-scope, or an into-scope event, and wherein the selective notification causes the return of the any matching data objects to the data request module by the management server for the portion of the subscribing applications.