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

[Lisa Dusseault]

> 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?).

That's certainly not my goal -- that would not be conducive to 
developing a standard, let alone to achieving interoperability.  My 
goal was to maximize interoperability and usability together, which of 
course trade off against each other.  Interoperability could be 
achieved almost trivially with a trivial standard but it wouldn't be 
very usable.  Usability could be maximized with a complex protocol but 
it would be only theoretical usability without good interoperability.  
CalDAV is a stab at a compromise there and I welcome input from this 
list on where the balance should lie.

> 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).

What do you think is too complex?  Evidently you think DASL is not too 
complex but Jabber is; that's interesting because it's not the same 
position others would necessarily take, since so many XMPP /Jabber 
libraries exist but few (none?) DASL libraries.

> 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 ;-)
>

Cyrus also proposed CalDAV "levels" where the first level was basically 
what Apple does with iCal, so an even simpler "Level 0" than what you 
propose.

The reason ACL is a requirement in CalDAV is because the requirements 
investigation that the CalSch WG did resulted in deciding that access 
control was a requirement for a calendar access protocol.   I don't 
think it's actually a requirement, but I'd like some kind of rough 
consensus before making it optional.

Lisa