1. Message Service System
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2. The Message System Paradigm
The Message System or Message-Oriented Middleware (MOM) paradigm is an elaboration of the basic message-passing paradigm.
A message system serves as an intermediary among separate, independent processes.
A message system acts as a switch for messages, through which processes exchange messages asynchronously, in a decoupled manner.
A sender deposits a message with the message system, which forwards it to a message queue associated with each receiver.
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3. The Message System Paradigm
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4. Message System Models Two subtypes of message system models:
Point-to-Point
Publish-Subscribe
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5. The Point-To-Point Message Model
A message system forwards a message from the sender to the receiver’s message queue. Unlike the basic message passing model, the middleware provides a message depository, and allows the sending and the receiving to be decoupled.
Via the middleware, a sender deposits a message in the message queue of the receiving process.
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.
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6. The Publish/Subscribe Message Model
Each message is associated with a specific topic or event. Applications interested in the 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 operation allows a process to multicast to a group of processes, and the subscribe operation allows a process to listen for such multicast.
This model offers a powerful abstraction for multicasting or group communication
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7. Toolkits based on the Message-System Paradigm
The MOM paradigm has had a long history in distributed applications.
Message Queue Services (MQS) have been in use since the 1980’s.
The IBM MQ*Series6 is an example of such a facility.
Other existing support for this paradigm are
Microsoft’s Message Queue (MSQ)
Java’s Message Service
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8. Short Message Service (SMS)
The transmission of short text messages to and from a mobile phone, fax machine and/or IP address.
Messages must be no longer than 160 alpha-numeric characters and contain no images or graphics.
Once a message is sent, it is received by a Short Message Service Center (SMSC), which must then get it to the appropriate mobile device.
The SMSC sends a SMS Request to the home location register (HLR) to find the roaming receiver.
Once the HLR receives the request, it will respond to the SMSC with the receiver’s status: 1) inactive or active 2) where receiver is roaming.
Ref:
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9. Short Message Service (SMS)
If the response is "inactive", then the SMSC will hold onto the message for a period of time.
When the receiver accesses his/her device, the HLR sends a SMS Notification to the SMSC, and the SMSC will attempt delivery.
The SMSC transfers the message in a Short Message Delivery Point to Point format to the serving system. The system pages the device, and if it responds, the message gets delivered.
The SMSC receives verification that the message was received by the receiver, then categorizes the message as "sent" and will not attempt to send again.
Ref:
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10. Sources of Information
Sun's JMS Tutorial
Microsoft's Message Queue(MSMQ)
IBM's MQ-Series
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