Network Working Group                                             E. Pot
Internet-Draft                                                fruux GmbH
Expires: December 29, 2016                                 June 27, 2016


                      CardDAV Address Book Sharing
                      draft-pot-carddav-sharing-00

Abstract

   This specification defines sharing address books between users on a
   CardDAV server.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on December 29, 2016.

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   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions Used in This Document . . . . . . . . . . . . . .   2
   3.  Address book sharing  . . . . . . . . . . . . . . . . . . . .   2
   4.  Handling multiple copies of a contact . . . . . . . . . . . .   2
   5.  Normative References  . . . . . . . . . . . . . . . . . . . .   3
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   3

1.  Introduction

   Users of CardDAV [RFC6352] often require a mechanism to share an
   address book with other users.

   Sharing address books is for the most part completely implemented
   using draft-pot-webdav-resource-sharing, but there are a few
   considerations specific to CardDAV to ensure that certain mechanisms
   still behaves as expected.

2.  Conventions Used in This Document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

   When XML element types in the namespaces "DAV:" and
   "urn:ietf:params:xml:ns:caldav" are referenced in this document
   outside of the context of an XML fragment, the string "DAV:" and
   "CALDAV:" will be prefixed to the element type names respectively.

3.  Address book sharing

   While the draft-pot-webdav-resource-sharing specification allows
   sharing of potentially any resource on a server, this specification
   only concerns itself with sharing address book collections, as
   defined in CardDAV [RFC6352].

   Sharing of resources other than address book collections is not
   addressed in this specification.

4.  Handling multiple copies of a contact

   vCard are often distributed via email, and two users of a CardDAV
   might have a copy of the same vCard.

   When those two users now share an addressbook, they might end up with
   two vCards that describe the same person.




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   Some address book user agents coalesce two vCards from different
   addressbooks to show up as one (merged) vCard to an end user.  These
   clients SHOULD ensure that when an update is made to a merged vCard,
   all instances of that vCard are updated if the user agent has read-
   write access.

   In case two vCards have conflicting information, the information from
   the vCard with the highest value for the REV property should be used.

5.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC4791]  Daboo, C., Desruisseaux, B., and L. Dusseault,
              "Calendaring Extensions to WebDAV (CalDAV)", RFC 4791,
              DOI 10.17487/RFC4791, March 2007,
              <http://www.rfc-editor.org/info/rfc4791>.

   [RFC6352]  Daboo, C., "CardDAV: vCard Extensions to Web Distributed
              Authoring and Versioning (WebDAV)", RFC 6352,
              DOI 10.17487/RFC6352, August 2011,
              <http://www.rfc-editor.org/info/rfc6352>.

   [RFC7303]  Thompson, H. and C. Lilley, "XML Media Types", RFC 7303,
              DOI 10.17487/RFC7303, July 2014,
              <http://www.rfc-editor.org/info/rfc7303>.

Author's Address

   Evert Pot
   fruux GmbH
   Koenigsstrasse 32
   Muenster, NRW  48143
   Germany

   Email: me@evertpot.com
   URI:   https://fruux.com/











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