A.3. MESSAGING STANDARDS

SOAP 1.2

SOAP is one of the foundational standards of SOA. Many other standards build on it. It stipulates the format of the messages exchanged between the applications.

SOAP requires that all messages be formatted according to XML. For example, an application requesting a price quote can formulate a request message as follows:

<Envelope>
<Body>
 <GetPriceQuote>
  <ProductId>41</ProductId>
 </GetPriceQuote>
</Body>
</Envelope></codeDisplayEnhanced>

The service provider application, upon receiving this request message can send a reply back as follows:

<Envelope>
<Body>
 <GetPriceQuoteResponse>
  <Price>32.95</Price>
 </GetPriceQuoteResponse>
</Body>
</Envelope>

Web Services use SOAP as the message format. In SOA, not all services are Web Services and consequently you do not have to use SOAP. However, to make your services interoperable, Web Services are an excellent choice. At minimum, services that you intend to expose to your customers, suppliers, and partners should be highly interoperable.

SOAP concerns itself only with the format of the messages. It does not stipulate exactly how the messages will be delivered. Today, most SOAP messages are exchanged using the HTTP protocol, the same protocol used by the Web browsers and Web servers. There is nothing stopping you from sending a SOAP message via e-mail, or simply by saving the message in a file.

Web Services Addressing

Exhibit A.3 shows an example of how two software applications can engage in a conversation. ...

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