What is SOAP?
SOAP stands for Simple Object Access Protocol. It is a protocol used for exchanging information in the implementation of web services. SOAP relies on XML (Extensible Markup Language) to format messages and usually relies on other application layer protocols, most notably HTTP and SMTP, for message negotiation and transmission.

Key Features of SOAP

Protocol-based: SOAP is a protocol, which means it has strict rules for messaging.
Language and Platform Independent: SOAP can be used on any platform and with any programming language.
Standardized: SOAP has a standardized set of rules, making it a reliable choice for communication between different systems.

Example of a Simple SOAP Request
Imagine you want to create a web service that provides weather information. A SOAP request to get the weather for a specific city might look like this:

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:web="http://www.example.com/weather">
   <soapenv:Header/>
   <soapenv:Body>
      <web:GetWeather>
         <web:CityName>New York</web:CityName>
      </web:GetWeather>
   </soapenv:Body>
</soapenv:Envelope>

In this XML, we have an Envelope, which is the top element in a SOAP message. Inside it, there is a Header (which is empty in this case) and a Body which contains the actual request. The GetWeather request asks for the weather in New York City.

Example of a Simple SOAP Response
The server might respond with the following SOAP message:

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">
   <soapenv:Header/>
   <soapenv:Body>
      <web:GetWeatherResponse>
         <web:CityName>New York</web:CityName>
         <web:Temperature>25</web:Temperature>
         <web:Condition>Sunny</web:Condition>
      </web:GetWeatherResponse>
   </soapenv:Body>
</soapenv:Envelope>

Here, the Envelope and Body are similar to the request. The GetWeatherResponse contains the weather information: the city name, temperature, and condition.

Conclusion
SOAP is a protocol used to exchange structured information in the implementation of web services. It is protocol-based, language, and platform independent, and standardized. By using XML for its messages, it ensures a high level of compatibility across different systems and platforms.

Understanding API Architecture Styles Using SOAP