Which format is primarily used for data exchange in SOAP services?

SOAP (Simple Object Access Protocol) is a protocol used for exchanging structured information in web services. The primary format utilized for data exchange in SOAP services is XML. This is because SOAP relies on XML for its message structure, which allows for the encoding of messages with a standardized format that can be easily understood by different systems.

XML provides a flexible and hierarchical way to represent data, making it suitable for the complex data structures that may be involved in service interactions. Additionally, SOAP messages are typically wrapped in an XML envelope, which contains both the header and the body, allowing for various properties like routing information to be included.

The other options, such as JSON, HTML, and YAML, serve different purposes. JSON is predominantly used in RESTful web services due to its lighter weight and ease of use with JavaScript. HTML, being a markup language for displaying web content, is not intended for data exchange. YAML, often used for configuration files, is not widely adopted for web service communications like SOAP. Thus, XML is clearly the format that aligns with the requirements and standards of SOAP services.