Client specified properties

I've read through the WEBDAV spec and Lisa's book, but there is one area 
that isn't quite clear to me.

Is it expected that a WEBDAV server should accept arbitrary dead 
properties that the client PROPPATCHs?

We've been watching the messages sent by Windows Explorer and we see 
that it sends several Windows specific properties in a PROPPATCH. Our 
system naturally has the required properties (or can leave them blank in 
specific cases). However, we do not have any need for arbitrary client 
specified properties. Does WEBDAV (clients, servers, or specifications) 
expect that we do have this capability?

Jeff Thompson