XML-binary Optimized Packaging
XML-binary Optimized Packaging (XOP) is a mechanism defined for the serialization of XML Information Sets (infosets) that contain binary data, as well as deserialization back into the XML Information Set. == Benefits == XOP allows the binary data part of an XML Infoset to be serialized without going through the XML serializer.
Source: Wikipedia — XML-binary Optimized Packaging (CC BY-SA 4.0)