In March 2007, the CalDAV specification was finished and published by the IETF as RFC 4791, authored by Cyrus Daboo (Apple), Bernard Desruissaux (Oracle), and Lisa Dusseault (CommerceNet).
CalDAV is designed for implementation by any collaborative software, client or server, that needs to maintain, access or share collections of events.
[clarification needed] 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.
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.