CalDAV

Calendaring Extensions to WebDAV, or CalDAV, is an Internet standard allowing a client to access scheduling information on a remote server. It extends WebDAV (HTTP-based protocol for data manipulation) specification and uses iCalendar format for the data. The protocol is defined by RFC 4791. It allows multiple client access to the same information thus allowing cooperative planning and information sharing. Many server and client applications support the protocol.

History

The CalDAV specification was first published in 2003 as an Internet Draft submitted to the Internet Engineering Task Force (IETF) by Lisa Dusseault. In March 2007, the CalDAV specification was described in the RFC 4791. CalDAV is designed for implementation by any collaborative software, client or server, that needs to maintain, access or share collections of events. It is developed as an open standard to foster interoperability between software from different implementers.

Specification

The architecture of CalDAV (partially inherited from the underlying specifications) organizes the data (events, tasks, free-busy info, notes) in directories (collections), where multiple items (resources) reside. The resources and collections can be accessed by one or more users, using standard HTTP and DAV semantics to detect conflicting changes, or to provide locking.

For access control the concept of ACLs are used, so each operation (view, edit, delete etc.) can be denied or granted per user. Therefore the specification requires that CalDAV servers must support "WebDAV Access Control Protocol" (RFC 3744). The calendar resources must use iCalendar format, which allows the server to understand and process the data. Parsing the iCalendar items is necessary, because the server has to support a number of calendaring-specific operations such as doing free-busy time reports and expansion of recurring events. With this functionality, a user may synchronize his or her own calendar to a CalDAV server, and share it among multiple devices or with other users. The protocol also supports non-personal calendars, such as calendars for sites or organizations.

Implementations

• Agendav, a web open source caldav client
• Apple iCal -- On August 7, 2006, Apple announced that Mac OS X 10.5 "Leopard" would include iCal 3.0, an application that supports the CalDAV access and scheduling standards. Mac OS X Server 10.5 Leopard includes iCal Server, which implements the CalDAV access and scheduling protocols. The iCal Server has been released under an open source license as the Darwin Calendar Server. On March 17, 2009, Apple Computer announced that CalDAV would be included in the iPhone 3.0 SDK.
• Atmail provides a complete client & server Calendaring solution - Based on the CalDAV protocol, Atmail provides a complete, full server implementation, and support for a wide range of desktop clients and mobile devices.
• DAViCal is an open source calendaring server that uses the CalDAV format compatible with multiple calendaring clients.
• EGroupware, a web-based open source groupware server, contains support for CalDAV since version 1.8
• Fabasoft Folio Cloud
• fruux, a synchronization service, supporting CalDAV
• Google Calendar supports CalDAV using iCal 3.x and Mozilla Sunbird 0.8+.
• Kerio Connect (formerly Kerio MailServer) - supports CalDAV since version 6.5
• The Mozilla Calendar Project applications (Lightning, a plugin for Thunderbird , Seamonkey internet suite and Sunbird (a standalone version) also support CalDAV calendars. Other freely available client software include Evolution, Mulberry and Chandler.
• OpenLink Data Spaces, a data integration framework and suite of associated Web applications
• OpenLink Virtuoso, a hybrid middleware and database server, since version 6.5 (Commercial Edition) and 6.1.5 (Open Source Edition)
• Oracle Beehive, a unified communication and collaboration software solution, supports a number of open standards including CalDAV. This allows Beehive to work with a number of calendaring clients including Apple iCal, Mozilla Lightning, and Mozilla Sunbird.
• SabreDAV, a WebDAV framework for PHP, supports CalDAV since version 1.2
• Synchronica, a developer of mobile push email and synchronization solutions announced that their Synchronica Mobile Gateway and Synchronica Mobile Backup products are both fully compatible with the CalDAV standard, allowing compatibility across a wide range of calendar applications.
• Tryton, an Open source platform for business solution, supports CalDAV server since version 1.4
• Yahoo! Calendar supports CalDAV using iCal 3.x.
• Zimbra

See also

• Comparison of CalDAV and CardDAV implementations
• Calendar
• CardDAV
• GroupDAV, an effort to create a simplified, straightforward protocol for calendars as well as contacts.
• iCalendar
• Scheduling OSID defines a software interface abstraction for calendaring protocols
• SyncML
• vCalendar
• WebDAV

External links

RFCs

• RFC 2616 – HTTP
• RFC 3744 – WebDAV Access Control Protocol
• RFC 4791 – CalDAV
• RFC 4918 – WebDAV
• RFC 5545 – iCalendar
• RFC 5546 – iTIP

Websites

• CalDAV Resource Site
• CalConnect, The Calendaring and Scheduling Consortium
• WebDAV Resources
• Baïkal, an open-source and lightweight CalDAV+CardDAV server