Re: [Evolution] Advice needed for Exchange-like calendaring

[Kees Cook <kees osdl org>]

On Tue, Jun 10, 2003 at 11:59:08AM -0700, Bryce Harrington wrote:
> Kees Cook is working on writing up a list of the features that would be
> nice to have from such a system, which he'll post here.

Here's the document I started.  The requirement list is at the bottom, but 
I think hits all the important things.  I'm sure there are more high-level 
requirements that should be added, though...


As a side-task of our Calendaring evaluation, we're hoping to write
something like a whitepaper outlining the design requirements for a
"real" open source solution to the calendaring void.  A lot of other
people have started this before, so this should serve as a list of
references and a brain-dump of requirements for the system to have.

Standards
~~~~~~~~~
Here is a quick run-down of the IETF standards for calendaring.

iCalendar is the text data format of calendaring information.  The analogy 
to email is an individual email in the "mbox format" (RFC822).
http://ietf.org/rfc/rfc2445.txt

iTIP (iCalendar Transport-independent Interoperability Protocol) is the 
method that iCalendar data is sent to other users (event scheduling, etc).
The analogy to email is the SMTP protocol for sending email to another 
user.
http://ietf.org/rfc/rfc2446.txt

iMIP (iCalendar Message-based Interoperability Protocol) is a defined 
binding of iTIP to Email messages.  This defines an iTIP communication 
over email systems, reducing the need for an iTIP server.
http://ietf.org/rfc/rfc2447.txt

CAP (Calendar Access Protocol) is the client-server protocol used by
clients to access a central calendar storage server.  The best analogy to
email is the IMAP protocol (RFC2060), which allows a client to manipulate
server-side folders.  This protocol is still an IETF draft.
http://www.imc.org/draft-ietf-calsch-cap


Sources
~~~~~~~
While searching for open source calendaring solutions, I found several 
interesting information sources:

ReefKnot has started implementations of the IETF standards (including
CAP), though activity recently appears quiet (last devel mailing
list post was Nov 2002).  They have written several good overviews.
See their "Publications" section for these documents, as well as the
"Works In Progress" for other whitepapers.
http://reefknot.sourceforge.net/

OpenCAP is a project that also looks like it's not currently active
(latest News item was Aug 2002), but has some documentation and some
design work done for developing a CAP server.
http://www.opencap.org/html/

A quick discussion I found on extracting Outlook information is here:
http://laughingmeme.org/archives/000281.html


Quick Requirements
~~~~~~~~~~~~~~~~~~
Here's a quick set of requirements as I see them right now for making a 
functional open source client/server Calendaring system.

server-side storage/scheduling
        - use get(pw|gr)* POSIX calls for local user list or may use 
          external system (LDAP?)
        - manages free/busy and on-server scheduling
        - manages delegation/read/write permissions
        - manages out-of-band scheduling notifications (email, pages, etc)
        - may manage scheduling events with off-site people (via iMIP or 
          CAP)
        - on-disk storage must be backup safe (no need to shut down server)

client-side synchronization
        - keep a local copy of calendar
        - resync and handling conflict resolution on reconnect

client-side scheduling
        - may manage scheduling calendar events with off-site people 
          (via iMIP and/or CAP)
        - may keep a list of "cached" users and free/busy from the server 
          so that offline scheduling can be done




-- 
Kees Cook
Open Souce Development Lab
kees osdl org