Service Oriented Architecture Field Guide for Executives

A.4. ADVANCED STANDARDS

Web Services Notification

Both plain SOAP messaging and Web Services Addressing suffer from a few limitations. The consumer must be aware of the address of the service provider. Also, the request message is sent to only one service provider. This type of one-to-one messaging cannot easily solve certain problems where there are potentially several service providers (Exhibit A.4).

Figure A.4. In some cases, the same message needs to be sent to a number of service providers

Any savvy buyer organization will send the price quote request to multiple sellers. Competition for price is the main reason for it. Also, not all buyers will have the product in stock. It is only prudent to contact several buyers. In a situation like this, it would be ideal where the buyer-side application did not have an intimate knowledge of the number and location of the seller service providers. These things should be configured outside of the consumer application.

Web Services Notification extends SOAP to make that possible. It allows the service providers to subscribe to certain events. When these events take place, the consumer publishes a message. All service providers that are interested in that message are then notified.

Web Services Reliable Messaging

When an application sends a SOAP message using the HTTP protocol, there is no guarantee that the receiver will get the message. ...