#2373 (Shared xDAV (CalDAV/CardDAV) resources are not discoverable) / Re: time for cyrus-imap v3.2?

[Дилян Палаузов]

Hello,

> *  #2373 (Shared xDAV (CalDAV/CardDAV) resources are not discoverable).
> Dilyan Palauzov sent a diff for this in the github repo and there was a
> discussion with Ken on possible implementations (shared xDAV resources):
> https://lists.andrew.cmu.edu/pipermail/cyrus-devel/2018-May/004263.html.
> I guess it had enough progress to try to close it.

as far as I remember there is some DAV sharing progress in the 3.2 upcoming release, but I do not know the details.  I
guess it handles just scheduling of events of shared/unowned calendars, but not the discovery.  At CalDAV level the
options for discovery of foreign collections are:
- clients (CUAs) support for sharing resources the model described at 
https://evertpot.com/webdav-caldav-carddav-sharing/ , or 
- CUAs they discover other users by utilizing the  DAV:princapal-property-search to discover the home-sets of another
user,  from there obtain the accessible calendars, and the CUA memorizes to which calendar it has subscribed.

I am not aware of any CUA which does anything of the above. The third option is

- CUAs do not change, but the server changes.  Once the properties of a home-set (user4/#calendars or
user7/#addressbooks ) have READ/LOOKUP righth, these home-sets are returned to the CUA, when CUA asks for the accessible
home-sets.  On the next step the CUA iterates over all returned home-sets and fetches the collections to which it has
access (READ/Lookup ACL).  If there is a calendar that does not belong to any user (created with hack command over
IMAP), then this calendar could be a part of a fictional /dav/calendars/user/anonymous at domain/ home-set.  Such no-owner
calendars have to my knowledge no-advantage over calendars belonging to the user/ namespace.

The advantage of the last method is, that clients do not have to add any new features.  The disadvantage is, that all
users see all calendars instantly they have access to, and these can be too much.  In particular, clients that have
implemented the first two models/workflows, do not have any advantage over clients which have not implemented that two
workflows.

Greetings
  Дилян