What distinguishes SOAP from REST?

• A. SOAP is a web service architectural style
• B. SOAP is a protocol that requires a WSDL file
• C. SOAP reads can be cached
• D. SOAP is faster than REST

Answer: (B)

SOAP, which stands for Simple Object Access Protocol, is primarily recognized as a protocol designed for exchanging structured information in web services. One of its key characteristics is the requirement for a Web Services Description Language (WSDL) file. This file acts as a contract between the service provider and the consumer, detailing the available methods, inputs, outputs, and how to communicate with the service. This structured approach is what sets SOAP apart from REST, which is an architectural style that does not require a WSDL specification.

In contrast, SOAP’s reliance on a WSDL file ensures that the client can generate requests accurately and handle responses effectively, making it integral to how SOAP operates. The other options do not accurately differentiate SOAP in the same way, as they misrepresent either the function, capabilities, or comparisons with REST.

For instance, while some SOAP messages may include caching mechanisms, the statement that SOAP reads can be cached is not a defining characteristic that separates it from REST. Similarly, the claim regarding speed lacks a consistent basis, as performance can vary based on implementation. Moreover, the idea that SOAP is an architectural style is incorrect, as it is fundamentally a protocol, which is distinct from the REST architectural style.