Responses
In response to a request, the Product Advertising API web service 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.
Item Attributes Segment
Assuming that your request is valid, the final segment of the response that contains the item attributes is typically the part of the response that contains the most value. This segment contains all of the descriptive information about the items that satisfied the request. In the preceding example, one item was found that satisfied the search criteria. Many attributes are returned that describe that item, including, the title, "Saving Miss Oliver's: A Novel of Leadership, Loyalty and Change."
The item attributes returned in a response vary according to the response group used and the items found. Merchants do not always provide Amazon with a single set of item attributes. For example, one merchant might supply the name of a book's publisher, another might not. A response contain both of these books would therefore contain a different set of item attributes. Item attributes that do not have values are not returned. The API Reference Guide describes the item attributes that can be returned by each response group.