A receiving process extracts the messages from its message queue, and handles each one accordingly. Compared to the basic message-passing model, this paradigm provides the additional abstraction for asynchronous operations. To achieve the same effect with basic a developer will have to make use of threads or child processes. The Publish/Subscribe Message Model: In this model, each message is associated with a specific topic or event. Applications interested in he occurrence of a specific event may subscribe to messages for that event. When the awaited event occurs, the process publishes a message announcing the event or topic. The middleware message system distributes the message to all its subscribers. The publish/subscribe message model offers a powerful abstraction for multicasting or group communication. The operation allows a process to multicast to a group of publish processes, and the operation allows a process to listen for such multicast. subscribe Remote Procedure Call: As applications grew increasingly complex, it became desirable to have a paradigm which allows distributed software to be programmed in a manner similar to conventional applications which run on a single processor. The Remote Procedure Call (RPC) model provides such an abstraction. Using this model, interprocess communications proceed as procedure, or function, calls, which are familiar to application programmers. A remote procedure call involves two independent processes, may reside on separate machines. A process, wishing to make a request to another process, issues a A, B, procedure call to passing with the call a list of argument values. As in the case of B, local procedure calls, a remote procedure call triggers a predefined action in a procedure provided by process At the completion of the procedure, process returns a value to B. B process A. RPC allows programmers to network applications using a programming construct similar to the local procedure call, providing a convenient abstraction for both interprocess communication and event synchronization. Since its introduction in the early 1980s, the Remote Procedure Call model has been widely in use in network applications. There are two prevalent APIs for Remote Procedure Calls. The evolved from the RPC Open Network Computing Remote Procedure Call, API originated from Sun Microsystems in the early 1980s.
A receiving process extracts the messages from its message queue, and handles each one accordingly. Compared to the basic message-passing model, this paradigm provides the additional abstraction for asynchronous operations. To achieve the same effect with basic a developer will have to make use of threads or child processes. The Publish/Subscribe Message Model: In this model, each message is associated with a specific topic or event. Applications interested in he occurrence of a specific event may subscribe to messages for that event. When the awaited event occurs, the process publishes a message announcing the event or topic. The middleware message system distributes the message to all its subscribers. The publish/subscribe message model offers a powerful abstraction for multicasting or group communication. The publish operation allows a process to multicast to a group of processes, and the subscribe operation allows a process to listen for such multicast. Remote Procedure Call: As applications grew increasingly complex, it became desirable to have a paradigm which allows distributed software to be programmed in a manner similar to conventional applications which run on a single processor. The Remote Procedure Call (RPC) model provides such an abstraction. Using this model, interprocess communications proceed as procedure, or function, calls, which are familiar to application programmers. A remote procedure call involves two independent processes, may reside on separate machines. A process, A, wishing to make a request to another process, B, issues a procedure call to B, passing with the call a list of argument values. As in the case of local procedure calls, a remote procedure call triggers a predefined action in a procedure provided by process B. At the completion of the procedure, process B returns a value to process A. RPC allows programmers to network applications using a programming construct similar to the local procedure call, providing a convenient abstraction for both interprocess communication and event synchronization. Since its introduction in the early 1980s, the Remote Procedure Call model has been widely in use in network applications. There are two prevalent APIs for Remote Procedure Calls. The Open Network Computing Remote Procedure Call, evolved from the RPC API originated from Sun Microsystems in the early 1980s.
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