Design and implementation of CORBA-based Subscription Server

The standard CORBA operation invocation model supports synchronous, one-way, and deferred synchronous interactions between clients and servers. However, this model is too restrictive for real-time applications. In particular, the model lacks asynchronous message delivery, does not support timed invocations or group communication, and can lead to excessive polling by clients. We have designed and implemented a subscription server based on the OMG Notification Service specification for the structured push style communication. In order to alleviate some of the restrictions with the standard CORBA invocation model, the Subscription Server supports asynchronous message delivery and allows one or more suppliers to send structured messages to one or more consumers. Event data can be delivered from suppliers to consumers without requiring these participants to know about each other explicitly. In addition to implementing most of the interfaces defined in the specification, the Subscription Server implements an additional advertiser interface which lets one discover all event types offered by the channel and subscribed by the consumers. Event filtering as well as quality of service properties, such as connection reliability and event reliability, are also provided. An Auction Alert application was developed to test the functionality of the subscription server.