A few internet references report that etags for the same underlying resource but with different representation (xml, json ...) should have different etags. That is currently not the case. Added code to allow incorporation of representation info into the etag. By default the representation is "json", but future patches can pass the representation down and modify flow to match requested representation.

The existence of this file enables the Zope product refresh option.
Read the Zope documentation for more info about product refresh.