Hi, I'm new to this list (and CalDAV in general), and apologize if this question has been asked before. A search of the 2008 archives came up empty. My question is about the use of X-CALENDARSERVER-ACCESS in the Darwin Calendar Server. But allow me to start with a little background: I wanted to see if iCal can handle private events when the calendar is hosted on a CalDAV-compliant server, and I came across this article: http://support.apple.com/kb/TS1694 , which suggests if the server supports private events, the option automatically unlocks in iCal. "Weird," I thought, as I have not seen any other Apple apps adapt themselves based on server capability. But sure enough, after downloading and configuraing darwin calendar, the private option appears in iCal. A colleague asked if it uses CLASS property as defined in RFC 2445, so I looked at the ics file, and found X-CALENDARSERVER-ACCESS instead. After a while I found caldav-privateevents.txt, which details how other CalDAV servers can also unlock the private option in iCal, but it doesn't explain why X-CALENDARSERVER-ACCESS was chosen over CLASS in the first place. Can someone explain this to me? I'm sure there's a reason. Thanks, Robert