IETF iCalendar

The IETF iCalendar RFC "defines the format for specifying iCalendar object methods. An iCalendar object method is a set of usage constraints for the iCalendar object. For example, these methods might define scheduling messages that request an event be scheduled, reply to an event request, send a cancellation notice for an event, modify or replace the definition of an event, provide a counter proposal for an original event request, delegate an event request to another individual, request free or busy time, reply to a free or busy time request, or provide similar scheduling messages for a to-do or journal entry calendar component. The iCalendar Transport-indendent Interoperability Protocol (iTIP, RFC 2446) is one such scheduling protocol..."

References:

• "Internet Calendaring and Scheduling Core Object Specification (iCalendar)." By Frank Dawson (Lotus Development Corporation) and Derik Stenerson (Microsoft Corporation). IETF Network Working Group, Request for Comments #2445. November 1998. Produced by the Internet Engineering Task Force Calendaring and Scheduling Working Group. Line-numbered version. [cache]
• "iCalendar Transport-Independent Interoperability Protocol (iTIP) Scheduling Events, BusyTime, To-dos and Journal Entries." By Frank Dawson, Ross Hopson, Steve Mansour, Steve Silverberg, Anik Ganguly, and Robert Moskowitz. IETF Network Working Group, Request for Comments #2446. November 1998. "This document specifies how calendaring systems use iCalendar objects to interoperate with other calendar systems. It does so in a general way so as to allow multiple methods of communication between systems. Subsequent documents specify interoperable methods of communications between systems that use this protocol. The document outlines a model for calendar exchange that defines both static and dynamic event, to-do, journal and free/busy objects. Static objects are used to transmit information from one entity to another without the expectation of continuity or referential integrity with the original item. Dynamic objects are a superset of static objects and will gracefully degrade to their static counterparts for clients that only support static objects. This document specifies an Internet protocol based on the iCalendar object specification that provides scheduling interoperability between different calendar systems. The Internet protocol is called the 'iCalendar Transport-Independent Interoperability Protocol (iTIP)'."
• "iCalendar Message-Based Interoperability Protocol (iMIP)." By By Frank Dawson, Steve Mansour, and Steve Silverberg. November 1998. IETF Network Working Group, Request for Comments #2447. November 1998. This iMIP document "specifies a binding from the iCalendar Transport-independent Interoperability Protocol (iTIP) to Internet email-based transports. Calendaring entries defined by the iCalendar Object Model are composed using constructs from RFC-822, RFC-2045, RFC-2046, RFC-2047, RFC-2048, and RFC-2049. This document is based on discussions within the Internet Engineering Task Force (IETF) Calendaring and Scheduling (CALSCH) working group..."
• "Building an RDF Model: A Quick Look at iCalendar." By Tim Berners-Lee. "I spent a few hours reading 50 pages of the iCalendar RFC2445 with a view to evaluating proposals to put it into XML. My conclusion early on was that the spec should be written in terms of RDF properties, particularly as it has a clear property/value and parameter/value structure..."
• iCalendar SIP-Based Interoperability Protocol. Reference: 'draft-pessi-calsch-isip-00'. October 2002. "This document, proposes a binding from the abstract iCalendar Transport-independent Interoperability Protocol (iTIP) using Session Initiation Protocol (SIP) as transport and SIP/SIPS URIs as addresses. This document proposes using the XML iCalendar or xCal as a mandatory payload format with SIP. XML iCalendar is an XML DTD that corresponds to the iCalendar, Internet Calendaring and Scheduling Core Object Specification defined by RFC 2445. SIP is a application-layer signaling protocol for creating, modifying, and terminating multimedia sessions, retrieving user presence and sending instant messages..."
• "Guideline for use of XML with iCalendar Elements." By Tim Hare. IETF Network Working Group, Internet Draft. Reference: 'draft-hare-xcalendar-00'. May 18, 2004, expires November 16, 2004. 46 pages. "This memo defines a guideline for using XML to represent calendaring information that corresponds to the iCalendar, Internet Calendaring and Scheduling Core Object Specifications..." IETF source: http://www.ietf.org/internet-drafts/draft-hare-xcalendar-00.txt.
• Beyond iCal downloads. "Extend your calendaring with these free applications: CalendarUpload, iCal FTP X, iCal2blog X, PHP iCalendar, Mozilla Calender and Sunbird..."

IETF xCal

The IETF xCal draft "defines a XML Document Type Definition (DTD) that corresponds to the iCalendar, Internet Calendaring and Scheduling Core Object Specification defined by RFC 2445. This DTD provides equivalent functionality to the standard format defined by 'Internet Calendaring and Scheduling Core Object Specification (iCalendar)'. Documents structured in accordance with this DTD may also be known as 'XML iCalendar' documents or 'xCal'..."

An attempt has been made to leverage the standard features of the XML syntax in order to represent the component iCalendar semantics. For example, strong data typing is specified using the XML notation declaration. The element type attributes are used to represent many of the calendar properties that provide a "global attribute" capability in an iCalendar object. Binary content in the ATTACH component property may either be specified through an external entity reference to a non-XML binary content or may be included in the XML document's content information, after first being encoding using the BASE64 scheme of RFC 2146. Parameter entities are used to logically group content particles in the XML DTD in order to facilitate reading and comprehension of the structure specified by the iCalendar XML DTD..." [excerpted from Version 02]

References:

• "iCalendar DTD Document (xCal)." By Frank Dawson (Nokia Corporation), Surendra K. Reddy (Oracle), Doug Royer (INET-Consulting LLC), and Eric R. Plamondon (Oracle). IETF Network Working Group, Internet-Draft. July 25, 2002, expires January 23, 2003. Reference: draft-ietf-calsch-many-xcal-02'. 53 pages.
• Version 01. February 15, 2002.
• Version 00. August 20, 2001.
• Mailing list archives for 'xcal-dev'. Maintained by INET-Consulting.com, Inc.
• "iCalendar DTD Document (xCal)" - Local reference page (2001)

IETF SkiCal

"SkiCal is a machine-readable format for the interchange of enhanced yellow-page directory listings. SkiCal expands the traditional property-set of name, address, telephone number and business category, adding structured information about people, places, things, activities and the conditions and terms for interaction with resources. SkiCal provides a structure for information about dates and times, directions, rules and recommendations for participation, pricing and reservation schemes, access information for those with special needs, ownership and responsibilities and promotional material. The referents of these listings, which are both events and persistent resources are referred to in this draft as SkiSources. SkiCal is based on and extends the iCalendar format as defined by RFC-2445, Internet Calendaring and Scheduling Core Object Specification (iCalendar). SkiCal objects are comprised of either VEVENT components with the addition of new properties and property parameters, or the SkiCal specific VOPTIME calendar component described in this memo..."

References:

• SkiCal - An Extension of iCalendar. By Greg FitzPatrick (SkiCal Consortium), Pär Lannerö (Metamatrix), and Niklas Hjelm (Soft Applications). IETF CALSCH Working Group. Reference: 'draft-many-ical-ski-06'. October 25, 2002, expires April 25, 2003.
• Announcement for version 06
• "SkiCal: A DAML+OIL Case Study." By Libby Miller (University of Bristol) and Greg FitzPatrick (SkiCal Consortium). "The iCalendar mime-directory standard is a format for describing events, to-do lists and journals, including associated date-formats, time zones, and alarms. It is used in the calendaring and scheduling applications of most major desktop and PDA personal information managers. SkiCal is an extension to iCalendar which describes public events such as concerts, sports competitions and conferences. DAML+OIL language constructs are capable of describing aspects of SkiCal objects such as price, age restrictions and start and end dates and times with precision and flexibility. SkiCal makes for a practical and useful potential application of DAML+OIL. In our presentation we describe the DAML+OIL language in general terms, and show some ways in which it can be of practical use for creating applications which store and retrieve SkiCal and other event-based information."

Calendaring and Scheduling Consortium

The Calendaring and Scheduling Consortium is "focused on the interoperable exchange of calendaring and scheduling information between dissimilar programs, platforms, and technologies. The Consortium's mission is to promote general understanding of and provide mechanisms to allow interoperable calendaring and scheduling methodologies, tools and applications to enter the mainstream of computing... The first Interop will be hosted by the University of California at Berkeley on its Berkeley campus on 29-30 July, 2004...

References:

• Calendaring and Scheduling Consortium. Announcement December 2004. "Seven vendors, six universities, two open source foundations, and a research facility form the founding membership of the Calendaring and Scheduling Consortium, which named David C. Thewlis the first Executive Director..."
• Calendaring and Scheduling Consortium web site
• Introduction
• URLs to items of interest for Calendaring and Scheduling

IETF Calendar Access Protocol (CAP)

[December 22, 2005] Update to RFC: Calendar Access Protocol (CAP). Edited by Doug Royer (IntelliCal, LLC), George Babics (Oracle), and Steve Mansour (eBay). IETF Network Working Group. Experimental Request for Comments #4324. 131 pages. "The Calendar Access Protocol (CAP) described in this memo permits a Calendar User (CU) to utilize a Calendar User Agent (CUA) to access an iCAL-based Calendar Store (CS). At the time of this writing, three vendors are implementing CAP, but it has already been determined that some changes are needed. In order to get implementation experience, the participants felt that a CAP specification is needed to preserve many years of work. Many properties in CAP which have had many years of debate, can be used by other iCalendar protocols." [source]

The Calendar Access Protocol (CAP) document 'specifies how a Calendar CUA interacts with a CS to manage calendar information. In particular, it specifies how to query, create, modify, and delete iCalendar components (e.g., events, to-dos, or daily journal entries). It further specifies how to search for available busy time information. Synchronization with CUAs is not covered and believed to be possible using CAP.

CAP is specified as a BEEP 'profile'. As such, many aspects of the protocol (e.g., authentication and privacy) are provided within BEEP. The protocol data units leverage the standard iCalendar format iCAL to convey calendar related information.

CAP can also be used to store and fetch iTIP objects and when those objects are used in this memo, they mean exactly the same as defined in iTIP. When iCalendar objects are transferred between the CUA and a CS, some additional properties and parameters may be added and the CUA is responsible for correctly generating iCalendar objects to non CAP processes.

The definition of new components, properties, parameter's, and value types are broken into two parts. The first part summarizes and defined the new objects. The second part provides the detail and any ABNF for those objects. The ABNF in CAP as in other iCalendar specifications is order independent. That is properties in a component may occur in any order and parameters in any property may occur in any order..." [adapted from version 11]

References:

• Calendar Access Protocol (CAP). Reference: 'draft-ietf-calsch-cap-11.txt'. July 27, 2003, expires January 25, 2004. IETF Calendaring and Scheduling Working Group. [source]
• CAP Issues list
• CAP Requirements. [source]
• "Blocks eXtensible eXchange Protocol Framework (BEEP)"

W3C RDF Calendar Taskforce - RDFiCal, RdfCalendar

The W3C RDF Calendar Taskforce is "an informal grouping of individuals interested in calendaring and scheduling, primarily in RDF. Through scenario-lead discussion by email and irc, the taskforce will aim to draft an RDF schema for calendar events. It will also aim to demonstrate the use of RDF in a calendaring and scheduling context. There is a great deal of work being done in the IETF in this area in particular in the IETF Calendaring and Scheduling (calsch) working group, The taskforce will monitor that work; this monitoring will result in a list of calendar resources on the taskforce's homepage. The taskforce is open to anyone interested in RDF calendaring and scheduling..."

"The www-rdf-calendar list is provided for detailed technical discussion of systems, vocabulary and scenarios relating to the use of RDF and XML with calendaring and scheduling tools on the Web."

"Some goals or use cases include:

• EventDiscovery
• CalendarScraping
• TravelTools, PathCross
• CalendarSynchronization
• ScheduleAnimation
• OpeningHoursUseCase
• AnnounceOMatic
• HTML views of calendars..."

References:

• RdfCalendar wiki
• RDF Calendar Taskforce
• Mail Archives for W3C list www-rdf-calendar@w3.org
• SWAD-Europe Workshop on the Semantic web and Calendaring October 09, 2002. Bristol, UK. See the meeting announcement.
• Semantic Web calendaring SWAD-Europe Deliverable 3.7, Developer Workshop Report 2.
• RDF Calendar Workspace
• Test directory
• "The RDF Calendar Task Force." By Leigh Dodds. From XML.com (July 25, 2001).
• RDF Calendar Notes
• "RDFiCal: iCalendar in RDF." By Libby Miller (Institute for Learning and Research University of Bristol) and Dan Connolly (W3C). Paper submitted to WWW2004. "This paper describes the development of RDFiCal, an RDF vocabulary (ontology) for describing calendar events based on the iCalendar standard (RFC 2445). It describes the reasons for creating the RDFiCal vocabulary and the iterative community process used to create it. It explains why we decided on a conversion process which was both highly automated and highly social, and describes why we think that modelling iCalendar in RDF is both feasible and useful..."
• "iCalendar to RDFical: a Semantic Web vocabulary created with community process-lite." By Libby Miller (ILRT, University of Bristol). Presentation to Intelligence, Agents, Multimedia Group, University of Southampton, 2003-11-03.

vCalendar Electronic Calendaring and Scheduling Exchange Format

[The proposed] "vCalendar(TM) defines a transport and platform-independent format for exchanging calendaring and scheduling information in an easy, automated, and consistent manner. It captures information about event and "to-do" items that are normally used by applications such as a personal information managers (PIMs) and group schedulers. Programs that use vCalendar can exchange important data about events so that you can schedule meetings with anyone who has a vCalendar-aware program..." [from Internet Mail Consortium]

References:

• vCard and vCalendar
• vCalendar: The Personal Calendaring and Scheduling Exchange Format. Version 1.0. White Paper. January 1, 1997.

RSS Event Module

From RDF Site Summary 1.0 Modules: Event: "With RSS we have the ability grab news and summaries from other websites and display them on our portals. However, a key property of news is that they describe something that just happened. Therefore the most interesting news are the newest news. Not so with events such as conferences, product launches, training courses etc. Events take place on a certain date in the future, and can be announced years or just a few days in advance. So when we announce them, we need to sort them on the date of the event. because the most interesting events are those that are going to happen in the near future.

Imagine that you have a calendar on your website. Imagine then that this calendar can be set up to automatically grab announcements of events from the O'Reilly events website, letting know when the next Perl/Open Source conference is -- or the next IRC chat with Tim -- or the release schedule for a new book. This is what the event module will provide... This specification is not a reimplementation of RFC2445 iCalendar in RDF. In particular, it lacks such things as TODO and repeating events, and there is no intention of adding those parts to the specification..."

Model (elements)

<ev:startdate> ( #PCDATA ) [W3CDTF] 
<ev:enddate> ( #PCDATA ) [W3CDTF] 
<ev:location> ( #PCDATA ) 
<ev:organizer> ( #PCDATA ) 
<ev:type> ( #PCDATA )

References:

• Namespace Declaration: xmlns:ev="http://purl.org/rss/1.0/modules/event/"
• RDF Site Summary 1.0 Modules: Event. Proposed draft. By Søren Roug (European Environment Agency). Draft 0.2. 2002-07-30.
• RSS events data display
• "Using an xhtml profile, RSS+events and XSLT to manage events information." By Libby Miller.

IPTC EventsML

[July 06, 2004] "IPTC Working Group Releases EventsML 1.0 Business Requirements Document." - A fourth Working Draft of EventsML 1.0 Business Requirements has been produced by members of the IPTC EventsML Working Group. 'EventsML' is the provisional name for a new IPTC standard designed for effective interchange of newsworthy event information. The objective of the International Press Telecommunications Council (IPTC) EventsML Working Group is to "create an XML format to be used in notifications of news worthy events such as press conferences for distributions to news media and others users who have an interest in the information for internal or external purposes." This IPTC standard for describing newsworthy events and associated coverage will address: (1) "Event publishing: communication of information about events, including associated media; (2) Event planning: managing the coverage of breaking news or upcoming newsworthy events, including support for gathering associated media; (3) Event coverage: communication of information about coverage of events by news organizations, often referred to as a 'Daybook'. The proposed standard would include linkage between resulting news packages and event coverage information." Use cases documented in the draft include Planned Event Coverage, News Agency Daybook, Sports League Publishes a Season Schedule, Urgent Breaking News, and Urgent Breaking News. The EventsML specification is intended to be useful to organizations outside the IPTC. A proposed requirement is that it be compatible with other IPTC standards, and that it reuse existing external standards where possible. EventsML should interoperate easily with existing IPTC standards, specifically with the IPTC Subject Reference System, NewsML, SportsML, and NITF." The vCard and vCalendar standards are explicitly identified as specifications which should inform EventsML in terms of interoperability. The designers believe it may be possible to implement most or all of the EventsML requirements using NewsML...

EventsML is one of the IPTC news initiatives. It proposes to "create an XML format to be used in notifications of news worthy events such as press conferences for distributions to news media and others users who have an interest in the information for internal or external purposes." Objectives in the design of the format, according to the 2003-06 Framework draft, include: (1) An XML format that can be a stand-alone or be incorporated into other IPTC standards; (2) Contains relationship entity for relating to and / or from a news item; (3) Ability to extend the use of EventsML as a notification tool but also incorporates into resource management such an assignment desk."

Alan Karben presented an overview at the News Standards Summit; see slide 20 in "SportsML and Other Payload MLs for News." EventsML is for listings that help find readers things to do, including: Event Name; Event Backers; Dates; Places; People (contacts and participants); Categories.

From the report of the IPTC 2003 Autumn Meeting:

It was agreed that the EventsML Working Party will be taken into the Special Content Working Party as it will fit in with other work and it should be possible to make better use of available resources. A brief update on progress made with EventsML since the last meeting was provided by Dominic Chan (Canada Newswire). Initial sets of requirements have been provided by interested parties, consolidated and compared to the existing formats. It appears that vCal and iCal already address 60% to 70% of the IPTC requirements, while both formats have extension facilities. However, neither of these formats is XML based.

Subsequent discussions confirmed that several members -- along with outside parties -- had a real need for an Events language. The main point to be settled was the best way of doing this. To begin with, would it be better to base the system on an existing system such as vCal (or iCal), or to make a totally fresh start? Then, should the program be a purely internal IPTC development our would it be better to approach OASIS to see if it would be possible to gain support for a more widely based development project?

It was pointed out that the support of three OASIS members is needed to form a discussion group. Since IPTC and Reuters are members it was decided to try to find an interested third party to form a group, and establish the general level of interest. An addition consideration is that involving OASIS in the development process could help ensure that details of the planned work are more widely known, and reduce the possibility of other initiatives trying to deal with the same requirements.

In parallel with this approach it was decided to start work on the production of a conceptual model for a possible XML Schema. If a co-operative venture is established this model could be made available as a basis for development, otherwise it can form the basis of an IPTC project. Assuming that a modular design approach is adopted, and sufficient efforts can be made, it is estimated that a completed standard might be available in 12 to 18 months. Since the meeting a new 'Conceptual Schema' folder has been added to the files area of the EventsML discussion group. This area is intended to contain prototype XML Schema for EventsML for discussion -- it already contains an overview..." [from IPTC Mirror newsletter #117, December 2003.]

References:

• IPTC EventsML web site
• EventsML 1.0 Business Requirements. Draft Version 4.
• EventsML Framework By Dominic Chan. IPTC Document Reference: EVT 0304. 2003-06-04. 9 pages. An overview of information gathered from IPTC members and the EventML-DVL group. [source .DOC from eventsML-dev]
• Draft EventML schema
• Prototype EventML schema. Graphic format.
• eventml-dev. The 'eventml-dev' list supports "development of EventML as resulted from October 2002 Amsterdam IPTC meetings. This group is open to all IPTC members who have interest in developing a standard for event listing."

Historical Event Markup and Linking (HEML)

"The Historical Event Markup and Linking project provides a means of coordinating and navigating disparate historical materials on the internet. It includes: (1) an XML schema for historical events which describes the events' participants, dates, location and keywords; the schema associates these with source materials in print or on the web. (2) XSLT stylesheets that combine conforming documents and generate lists, maps and graphical timelines out of them. HEML integrates these resources using the Cocoon web publishing engine..."

References:

• HEML web site
• Historical Event Markup and Linking" - Local reference page

Principal References

• Calendaring Extensions to WebDAV (CalDAV). Version -05. February 10, 2005.
• CalDAV Resources
• Ietf-caldav: Discussions on Calendar Access protocol based on WebDAV
• Calendaring and Scheduling Extensions to WebDAV (CalDAV). 'draft-dusseault-caldav-04'. December 13, 2004. History.
• Calendar Server Extensions for WebDAV (CalDAV). See the HTML version and announcement of 2003-12-18. [IETF ephemeral source URL]
• IETF CALSCH Working Group
  • IETF Calendaring and Scheduling (calsch) Working Group Charter
  • CALSCH Working Group home page
  • Guide to Internet Calendaring
  • CALSCH Internet Documents, Drafts and Issues
  • Web site for the ietf-calendar mailing list
• Related IETF Subgroups
  • WebDAV Access Control Protocol
  • DeltaV. A working group developing a protocol for versioning and configuration management of DAV repositories.
  • DASL (DAV Searching and Locating). A working group developing a protocol for searching DAV repositories.
• WEBDAV Resources:
  • IETF WEBDAV Working Group Home Page
  • IETF WEBDAV Working Group Charter
  • WebDAV Resources
  • "WEBDAV (Extensions for Distributed Authoring and Versioning on the World Wide Web)" - Main reference page.