When the Product Advertising API receives a request, it returns an XML document that contains the results of the call in an XML data structure. This data conforms to a WSDL and schema.
For REST requests, this data structure is simply the body of the HTTP response. You can use a data binding method for REST responses, or use an XML parser directly to process the information.
For SOAP requests, the data structure is the SOAP message body of the response. SOAP toolkits typically convert the response data into structures for use with your programming language, or allow you to specify your own data bindings.
Other than the use of a message envelope in the SOAP response, REST and SOAP responses are identical. Both conform to the Product Advertising API schema. The SOAP WSDL imports an XSD file to define the response messages. REST users can access the XSD file directly. For more information, see WSDL Location.