Linking and Publishing Custom Properties
Word documents use two custom properties to enable linking and publishing. First,
_SourceUrl is the address of the source library that a
document workspace uses when you choose Publish to Source Location. _SharedFileIndex is the site ID Word uses to locate the document workspace when
you open a linked file from your computer.
Of the two, _SourceUrl is the most straightforward since it contains a simple web address.
The _SharedFileIndex property is a much longer value that
identifies the document in the workspace. Figure
6-12 shows both custom properties in Word.
In the previous section,
"Linking Documents to Libraries," I instructed you to set the _SourceUrl manually to enable publishing from a linked document. That might
seem like a hack, but it's the only way I know. Word doesn't enable both features, even
though they are useful when combined.

Figure 6-12. Linking and publishing custom properties
For you programmers out there: the value of _SharedFileIndex is a GUID identifying the attachment in the list. You can
retrieve that information using the FindDwsDoc method of
the DWS web service.