The XML physical format is the simplest of the physical formats for modeling multipart messages, the content and the structure of the message are both fully described by the bit stream. The logical model must include an embedded message definition at the appropriate position, but there are no extra definitions required.
In the MRM domain, embedded XML messages are recognized by matching their XML tag name against the XML name of a message definition in the message model. If the position of the embedded message corresponds to an embedded message definition in the logical model, the message is recognized.
If the embedded message definition is a complex type, the message definition will contain a complex element based on that complex type. This complex element will have its own tag, which will appear in the bit stream before the tag for the embedded message. If you want to avoid this extra tag, you can create the embedded message definition from a group, and insert the group at the appropriate position in the message model.
You can define the outer message to contain more than one hierarchy of embedded messages, and you can define an embedded message to contain another embedded message. An embedded message, wherever it occurs, must start with the tag for that message.