The performance of GET processing needs to be efficient. To resolve a URL, it is not acceptable to have to traverse the URL tree to find out where the references are. High performance servers would not implement this. You have to make a trade-off between the flexibility you get from references and speed. It will look to them as if we still obey the namespace consistency constraints.
Many servers do.
Jim W doesn't like this. According to WebDAV, if you are a DAV resource and your parent is, too, then your parent must contain your url as part of its state. In our example, there is no parent collection. Jim will write up the alternative interpretations and his concerns. Judy will add this to the issues list.