Which data format does SOAP (Simple Object Access Protocol) support?

SOAP (Simple Object Access Protocol) primarily supports XML (eXtensible Markup Language) as its data format. This protocol is designed for exchanging structured information in web services, and XML serves as the foundation for its message format. SOAP messages are formatted in XML, which allows for the encoding of complex data types and structures, facilitating effective communication between systems over the internet.

Using XML allows SOAP to include a wide range of data types and provides a standardized way to transmit data. The structure of XML helps ensure that messages are both machine-readable and human-readable, enabling easier debugging and validation of data exchanges. This attribute is particularly important in web services where interoperability between different systems is crucial.

The other options listed do not align with the primary functions of SOAP. JSON, YAML, and HTML each serve different purposes and would not be suitable as the underlying format for SOAP messages. JSON is often used in RESTful APIs due to its lightweight nature, YAML is favored for configuration files and data serialization, and HTML is used for structuring content on the web, but none of these formats are utilized within SOAP protocols.