Cullen was talking about service discovery techniques that go beyond what I was aware of

• I thought that the most you could discover with DNS SRV records was the domain name. E.g. look up an SRV record for "CALDAV" type service and it would tell you "caldav.osafoundation.org" or "share.osafoundation.org"and nothing more.
• "OPTIONS *" is a hook a client could use to discover if "share.osafoundation.org" supported WebDAV or CalDAV, and possibly even to find what the principal URL namespace is or the general location of calendars
• Cullen says that it's trivial to advertise a path instead of only advertising a server. so the CALDAV SRV record could advertise "share.osafoundation.org/calendars".
• What if there isn't one namespace for calendaring but it's scattered throughout the server?
• Cullen mentioned ENUM and PKI innovations to discover the certificate or other information for a user, not just for a service. E.g. ENUM would allow one to start from a phone number, and from there discover specific properties about the user with that phone number, for example a SIP server address.