Path to file from which window has been opened

Question

If one opens a TextEdit file on a volume other than the startup volume, a window opens using the TextEdit application installed on the Startup volume. (At least, that's my conclusion as to what happens).
At that point, both 'windows of application "TextEdit"' or 'documents of application "TextEdit"' yield a wealth of information about the opened window, including (in different ways) the path to the originating file.
There are other applications for which that path information can be determined in a similar fashion.
But for other applications (most, it seems) the path to the originating file cannot be obtained in this manner. For example, if a Safari webarchive file is opened, much or most of the information about the resultant window is in 'windows of ...' or in 'documents of ...' -- but path information is typically listed as "empty" or "missing value."
How would one go about getting the path information in these cases? Basically, what's known initially is:
1) The name of the window
2) The application that opened the window
Information that can be added easily includes the window id and a few other things.

Answer 1

99.9% of what you see in Safari isn't file based, so it makes no sense for Apple to implement a file-based hook to its documents - there simply isn't a file to reference.
In the cases where you are opening a file on disk then the URL property will give you that information - if it begins with 'file://' then the window is pointing to a disk-based file, if it's 'http://' or "https://' then it's web-based.
Other applications will have similar issues depending on how they work. Take Mail.app, for example - mail messages are not stored in individual files, so it isn't possible to get the file reference to an email message. So it all depends on the app.