Unlike the other Office applications, the Word object model enables the developer to access the Open XML file format of a document while the document is open in the application. The content can be read using the Range.WordOpenXML property and information can be written to the document using the Range.InsertXML method.
In both cases, the information read from or passed to the document is in the so-called Open XML “flat file” format. Rather than the parts being separate xml file in a zip package, all the information is in one XML “string”, each part being a separate element.
Theoretically, the developer should be able to get a snapshot of the current document state using Document.Content.WordOpenXML. In practise, this is not 100% reliable because not all the document parts are converted into WordOpenXML, such as customization parts containing keyboard shortcuts. But up until now, we could be reasonably sure all significant content was present. We can hope that Microsoft puts a high priority on getting this oversight fixed in an early Service Pack.