Compound documents often contain objects that don't actually exist in their assembled form until they reach their destination. None of the current mechanisms of handling binary data in XML can efficiently represent compound documents. Multimedia systems, for instance, are just one example of systems requiring the processing of a number of large binary files, often simultaneously. Borden's Synapse system is based on compound document technology that integrates medical images with voice dictations, drawings, and textual reports. In XML-enabling this system, Borden had to devise a mechanism to represent compound documents.
Individual parts represent individual streams in the compound document.
This is, in essence, a compound document. Typically the first object in a message is in XML format. Other objects may be GIF, JPEG, or other binary formats. The whole package travels together so that once the message gets through a firewall, the links remain valid. Listing 2 shows the structure of this message.