Overview

The ODP/OMG CosTrading service is similar to a search engine for CORBA object service references. Figure 1 presents the CosTrading standard use, composed of four steps. (1) Service designers define their service offer types (see section 2.2). (2) Service providers or application servers characterize and export their service offers using properties describing the service. (3) Service users or client applications search service references using criteria describing their requirements. (4) Once references have been retrieved, clients invoke operations on the services. All these requests--definition, export, lookup, and use--are carried by CORBA.

Figure 1: The ODP/OMG CosTrading Service Use.

The CosTrading service provides three main interfaces for applications. The ServiceTypeRepository interface is used to define and manage service offer types. The Register interface is used to export service offers. Finally, the Lookup interface is used to search exported service offers. Other interfaces are also available for administration purposes, like to set the behavior of the trader and its search operation, as well as to build trader federations--offering a potentially large-scaled and unified trading service [2].