XML-Binary Optimised Packaging (XOP)

XOP defines how to efficiently serialize XML Infosets that have certain types of content by:

• Packaging the XML in some format. This is called the XOP package. The specification mentions MIME Multipart/Related but does not limit it to this format.
• Re-encoding all or part of base64binary content to reduce its size.
• Placing the base64binary content elsewhere in the package and replacing the encoded content with XML that references it.

XOP is used as an implementation of the MTOM specification, which defines the optimization of SOAP messages. Because these two specifications are so closely linked, they are normally referred to as MTOM/XOP.