Trading Object Service
Zahir Tari, Omran Bukhres PhD · 2001
In Chapter 7 we saw how objects can be found by using the CORBA Naming Service when their names are known. One problem that may arise is that the users do not have details about the names that are associated with different objects, but they have details about their (external) properties, such as the cost of printing a file. To enable the creation of objects in such a way, another service is defined, called the trading service, that is responsible for locating objects when the values of their properties are known. This chapter explains the details of the CORBA Trading Object Service (TOS). Before introducing the different elements of the TOS, we will show an example of how a TOS is used. The JTrader, which is a CORBA-compliant syntax will be used to illustrate the use of different trader operations, such as registering and importing a service type. Details about the elements of the CORBA TOS, and the trading policies, such as scoping policies, associated with CORBA traders are provided. Because query routing is very important when dealing with large-scale distributed applications. We explain the underlying model of the OMG query propagation mechanism and later show how this mechanism can be extended to deal with dynamic information related to service offers. Finally, in we provide a short description of some existing CORBA TOS implementations.