[GroupDAV] Lightning via CalDAV <--> GroupDAV

[Helge Hess]

On 26.10.2007, at 08:32, Ralf Becker wrote:
> I'm working on the GroupDAV interface for eGroupWare  
> (www.egroupware.org).
>
> I want to know what extra methods are required on top of the regular
> GroupDav ones, to support lightning via CalDAV? Are there any
> experiences what is required, or even better documentation ;-)

You would need to support all of CalDAV if you want to support  
Sunbird/Lightning in a reliable way. Even if it uses a subset right  
now, which subset that is can change every other version.

(Of course the Inverse GroupDAV addressbook provider for Lightning  
does just GroupDAV, so you should be clear with that)


> Btw. I like the idea mentioned here earlier by Helge, to define a
> GroupDAV 2.0, which contains the subset of CalDAV necessary to support
> lightning and the apple iCal client.

Thats definitely not what I mentioned, after all its impossible to do  
this. GroupDAV only makes sense if its supported by the clients (if  
they agree to stick to a "GroupDAV 2.0" subset and/or downgrade on  
the fly [if they detect 5xx codes on CalDAV ops]).

What I suggested was to enhance GroupDAV with one specified CalDAV  
REPORT to support bulk retrieval of items. "CalDAV REPORT" to make it  
easier for server to support CalDAV *and* GroupDAV.
I could use such a REPORT to speed up my GroupDAV Outlook/MAPI  
provider, but it will be useful for other clients too, eg the  
Funambol one.


Maybe a small list helps:
GroupDAV client
- very easy to make it talk to any full CalDAV server (just add support
   for the additional WebDAV resourcetypes)
CalDAV client
- doesn't work against GroupDAV servers (CalDAV requires ~100times the
   features in the server). To support GroupDAV it usually require a bit
   of additional code and awareness that the server might support less
GroupDAV server
- usually won't work against CalDAV clients unless it also supports
   CalDAV. Implementing GroupDAV first is a good starting point to
   enhance it to a full CalDAV server.
CalDAV server
- full support for CalDAV clients. Doesn't really need to do anything
   special to support GroupDAV clients. GroupDAV clients can be easily
   enhanced to support CalDAV servers in "GroupDAV mode".
   [Reminder for me: GroupDAV should specify that CalDAV collection  
types
    MUST be recognized as the respective GroupDAV collections by  
clients]


I think in the case of Sunbird/Lightning we could probably talk/ 
support the MailCo into supporting GroupDAV too (properly fall back  
to just GroupDAV if the server doesn't support CalDAV). I've failed a  
few bugreports with Mozilla in the past and never got negative/ 
unreasonable feedback.

Wrt to Apple iCal, if you do not want to provide a rather complete  
CalDAV implementation (and Apple iCal makes *HEAVY* use of a lot of  
CalDAV [+WebDAV ACL] features), we are back to Mathew's iSync plugin  
for GroupDAV.
He promised a OSX 10.5 version ;-)

Greets,
   Helge
-- 
Helge Hess
http://www.helgehess.eu/