[Ietf-caldav] Re: Notifications [was Re: Client work]

[Helge Hess]

On Aug 13, 2004, at 18:06, Lisa Dusseault wrote:
> It's my opinion that we can do much better than HTTP for notifications 
> if we're willing to work a little harder!

Yes, I absolutely agree. Using Jabber for that is certainly a good and 
reliable approach. The only issue I have with that is that it adds 
another relatively complex component to the server infrastructure 
(while httpu is pretty easy to implement).

But can we agree that this is out of scope for the "basic" CalDAV 
specification or an "optional" part, eg using protocol levels like in 
WebDAV?

Personally my goal is too bring as many _available_ servers and clients 
together - I'm not sure about your intention (produce a spec which 
covers all features of Chandler?).
Currently the only "protocol" which is more or less interoperable 
between servers is iCal-File-over-HTTP. And this one is really 
inappropriate for almost anything ;-)

For OGo we "solve" the situation only by implementing all the various 
protocols starting with iCal/HTTP, Exchange WebDAV, WCAP, 
XML-RPC(variants), RSS etc used by the clients. It is a mess that this 
is required even for basic things.
To summarize: my _strong_ fear is that if CalDAV ends up being too 
complex, few will implement it. The mentioned notification is certainly 
one thing which would require a major amount of work in existing 
servers (including OGo and PHPgroupware).

Maybe the "level" idea is good?:
CalDAV Level 0: basic DAV/iCal storage of iCal objects + DASL queries
CalDAV Level 1: Level 0 + more complex cal support (fanout, reports?)
CalDAV Level 2: Level 1 + Jabber notifications
What do you think? A calendaring system can work without level 1 and 2 
features. Instead of levels we could also use separate documents (like 
WebDAV ACL and DASL is separate from WebDAV and certainly not required 
for a lot of clients).

(BTW: I think it is already hard enough to make other server vendors 
implement DAV/DASL/ACLs properly ..., I already did a lot of talks with 
PHPgroupware and exchange4linux people on this ;-)

Greets,
   Helge
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