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Versions: 00 01 02 03 04 05 06 07 08 09 10 11 RFC 6321

Network Working Group                                           C. Daboo
Internet-Draft                                               Apple, Inc.
Intended status: Standards Track                             M. Douglass
Expires: September 9, 2010                                           RPI
                                                                 S. Lees
                                                               Microsoft
                                                           March 8, 2010


                   xCal: The XML format for iCalendar
                 draft-daboo-et-al-icalendar-in-xml-02

Abstract

   This specification defines a format for representing iCalendar data
   in XML.

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on September 9, 2010.

Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of



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   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the BSD License.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Conventions Used in This Document  . . . . . . . . . . . . . .  4
   3.  Converting from iCalendar to XML . . . . . . . . . . . . . . .  4
     3.1.  Pre-processing . . . . . . . . . . . . . . . . . . . . . .  5
     3.2.  iCalendar stream (RFC5545 section 3.4) . . . . . . . . . .  5
     3.3.  Components (RFC5545 section 3.6) . . . . . . . . . . . . .  6
     3.4.  Properties (RFC5545 section 3.5) . . . . . . . . . . . . .  7
       3.4.1.  Special Cases for Properties . . . . . . . . . . . . .  8
         3.4.1.1.  Multi-valued Properties  . . . . . . . . . . . . .  9
         3.4.1.2.  GEO Property . . . . . . . . . . . . . . . . . . .  9
         3.4.1.3.  REQUEST-STATUS Property  . . . . . . . . . . . . .  9
     3.5.  Parameters (RFC5545 section 3.4) . . . . . . . . . . . . .  9
       3.5.1.  VALUE parameter  . . . . . . . . . . . . . . . . . . . 11
     3.6.  Values (RFC5545 section 3.3) . . . . . . . . . . . . . . . 11
       3.6.1.  Binary (RFC5545 section 4.3.1) . . . . . . . . . . . . 11
       3.6.2.  Boolean  (RFC5545 section 4.3.2) . . . . . . . . . . . 11
       3.6.3.  Calendar User Address (RFC5545 section 4.3.3)  . . . . 11
       3.6.4.  Date (RFC5545 section 4.3.4) . . . . . . . . . . . . . 12
       3.6.5.  Date-Time (RFC5545 section 4.3.5)  . . . . . . . . . . 12
       3.6.6.  Duration (RFC5545 section 4.3.6) . . . . . . . . . . . 12
       3.6.7.  Float (RFC5545 section 4.3.7)  . . . . . . . . . . . . 12
       3.6.8.  Integer (RFC5545 section 4.3.8)  . . . . . . . . . . . 12
       3.6.9.  Period of Time (RFC5545 section 4.3.9) . . . . . . . . 12
       3.6.10. Recurrence Rule (RFC5545 section 4.3.10) . . . . . . . 13
       3.6.11. Text (RFC5545 section 4.3.11)  . . . . . . . . . . . . 13
       3.6.12. Time (RFC5545 section 4.3.12)  . . . . . . . . . . . . 13
       3.6.13. URI (RFC5545 section 4.3.13) . . . . . . . . . . . . . 13
       3.6.14. UTC Offset (RFC5545 section 4.3.14)  . . . . . . . . . 13
     3.7.  Extensions . . . . . . . . . . . . . . . . . . . . . . . . 14
   4.  Converting from XML into iCalendar . . . . . . . . . . . . . . 14
     4.1.  Converting XML Extensions into iCalendar . . . . . . . . . 14
     4.2.  The XML property for iCalendar . . . . . . . . . . . . . . 14
   5.  Handling link elements in XML and iCal . . . . . . . . . . . . 15
     5.1.  Links in xCal documents  . . . . . . . . . . . . . . . . . 16
     5.2.  The location relation type . . . . . . . . . . . . . . . . 16
     5.3.  The LINK property for iCalendar  . . . . . . . . . . . . . 16
     5.4.  Converting links between xCal and iCalendar  . . . . . . . 18
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 18
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 18



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     7.1.  Namespace Registration . . . . . . . . . . . . . . . . . . 19
     7.2.  Media Type . . . . . . . . . . . . . . . . . . . . . . . . 19
   8.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 20
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 20
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 20
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 21
   Appendix A.  Relax NG Schema . . . . . . . . . . . . . . . . . . . 21
   Appendix B.  XML Stylesheet for conversion to iCalendar  . . . . . 44
   Appendix C.  Example . . . . . . . . . . . . . . . . . . . . . . . 44
     C.1.  iCalendar Data . . . . . . . . . . . . . . . . . . . . . . 44
     C.2.  XML Data . . . . . . . . . . . . . . . . . . . . . . . . . 45
   Appendix D.  Change History (to be removed prior to
                publication as an RFC)  . . . . . . . . . . . . . . . 45






































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1.  Introduction

   The iCalendar data format [RFC5545] is a widely deployed interchange
   format for calendaring and scheduling data.  While many applications
   and services consume and generate calendar data, iCalendar is a
   specialized format that requires its own parser/generator.  In
   contrast, XML-based formats are widely used for interoperability
   between applications, and the many tools that generate, parse, and
   manipulate XML make it easier to work with than iCalendar.

   The purpose of this specification is to define "xCal", an XML format
   that allows iCalendar data to be converted to XML, and then back to
   iCalendar, without losing any semantic meaning in the data.  Anyone
   creating XML calendar data according to this specification will know
   that their data can be converted to a valid iCalendar representation
   as well.

   Two key design considerations are:

      Round-tripping (converting an iCalendar instance to XML and back)
      will give the same result as the starting point.

      Preserve the semantics of the iCalendar data.  While a simple
      consumer can easily browse the calendar data in XML, a full
      understanding of iCalendar is still required in order to modify
      and/or fully comprehend the calendar data.

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 namespace
   "urn:ietf:params:xml:ns:icalendar-2.0" are referenced in this
   document outside of the context of an XML fragment, the string
   "ICAL:" will be prefixed to the element types.

   Some examples in this document contain "partial" XML documents used
   for illustrative purposes.  In these examples, three periods "..."
   are used to indicate a portion of the document that has been removed
   for compactness.

3.  Converting from iCalendar to XML

   This section describes how iCalendar data is converted to XML using a
   simple mapping between the iCalendar data model and XML elements.




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3.1.  Pre-processing

   iCalendar data uses a line folding mechanism to limit lines of data
   to a maximum line length (typically 72 characters) to ensure maximum
   likelihood of preserving data integrity as it is transported via
   various means (e.g., email) - see Section 3.1 of [RFC5545].  Prior to
   converting iCalendar data into XML all folded lines MUST be unfolded.

   iCalendar data uses an "escape" character sequence for text values
   and parameter values.  When such text elements are converted into XML
   the escaping MUST be removed.

   iCalendar uses a base64 encoding for binary data.  The base64
   encoding MUST remain when converted to XML.

3.2.  iCalendar stream (RFC5545 section 3.4)

   At the top level of the iCalendar object model is an "iCalendar
   stream".  This object encompasses multiple "iCalendar objects".  In
   XML, the entire stream is contained in the root ICAL:icalendar XML
   element.

   An iCalendar stream can contain one or more iCalendar objects.  Each
   iCalendar object, delimited by BEGIN:VCALENDAR and END:VCALENDAR, is
   enclosed by the ICAL:vcalendar XML element.

   Example:

     <?xml version="1.0" encoding="utf-8"?>
     <icalendar xmlns="urn:ietf:params:xml:ns:icalendar-2.0">
       <vcalendar>
       ...
       </vcalendar>
     </icalendar>

   iCalendar objects are comprised of a set of "components",
   "properties", "parameters" and "values".  A "component" can contain
   other "components" or "properties".  A "property" has a value and
   optionally a set of "parameters".

   In XML, "components" are contained within an ICAL:components XML
   element.  With that element, another ICAL:components element could
   appear (representing components nested within components) or the
   ICAL:properties XML element could appear.  ICAL:properties is used to
   encapsulate iCalendar properties.

   Each iCalendar property will be mapped to its own XML element as
   described below.  Within each of these elements there is an optional



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   ICAL:parameters XML element used to encapsulate any iCalendar
   parameters.  Additionally there will be one or more XML elements
   representing the value of the iCalendar property.

   Example:

     <?xml version="1.0" encoding="utf-8"?>
     <icalendar xmlns="urn:ietf:params:xml:ns:icalendar-2.0">
       <vcalendar>
         <properties>
         ...
         </properties>
         <components>
         ...
         </components>
       </vcalendar>
     </icalendar>

         +------------------+----------------+------------------+
         | Item             | XML element    | XML Definition   |
         +------------------+----------------+------------------+
         | iCalendar Stream | ICAL:icalendar | Appendix A # 3.4 |
         | VCALENDAR        | ICAL:vcalendar | Appendix A # 3.6 |
         +------------------+----------------+------------------+

3.3.  Components (RFC5545 section 3.6)

   Each calendar component in the VCALENDAR object, delimited by BEGIN
   and END, will be converted to an enclosing XML element with the same
   name, but in lowercase:

            +-----------+----------------+--------------------+
            | Component | XML element    | XML Definition     |
            +-----------+----------------+--------------------+
            | VEVENT    | ICAL:vevent    | Appendix A # 3.6.1 |
            | VTODO     | ICAL:vtodo     | Appendix A # 3.6.2 |
            | VJOURNAL  | ICAL:vjournal  | Appendix A # 3.6.3 |
            | VFREEBUSY | ICAL:vfreebusy | Appendix A # 3.6.4 |
            | VTIMEZONE | ICAL:vtimezone | Appendix A # 3.6.5 |
            | STANDARD  | ICAL:standard  | Appendix A # 3.6.5 |
            | DAYLIGHT  | ICAL:daylight  | Appendix A # 3.6.5 |
            | VALARM    | ICAL:valarm    | Appendix A # 3.6.6 |
            +-----------+----------------+--------------------+








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3.4.  Properties (RFC5545 section 3.5)

   iCalendar properties , whether they apply to the VCALENDAR object or
   to a component, are handled in a consistent way.

   iCalendar properties are enclosed in the XML element ICAL:properties.

   Each invidivual iCalendar property is represented in XML by an
   element of the same name as the iCalendar property, but in lowercase.
   For example, the CALSCALE property is represented in XML by the ICAL:
   calscale element.

   Example:

     <?xml version="1.0" encoding="utf-8"?>
     <icalendar xmlns="urn:ietf:params:xml:ns:icalendar-2.0">
       <vcalendar>
         <properties>
           <calscale>...</calscale>
           <version>...</version>
           <prodid>...</prodid>
         </properties>
         <components>
         ...
         </components>
       </vcalendar>
     </icalendar>

   Each property can contain an ICAL:parameters XML element
   encapsulating any iCalendar parameters associated with the iCalendar
   property.

   Each property will contain one or more "value" XML elements as
   described below representing the value of the iCalendar property.

   +------------------+-----------------------+-----------------------+
   | Property         | XML element           | XML Definition        |
   +------------------+-----------------------+-----------------------+
   | CALSCALE         | ICAL:calscale         | Appendix A # 3.7.1    |
   | METHOD           | ICAL:method           | Appendix A # 3.7.2    |
   | PRODID           | ICAL:prodid           | Appendix A # 3.7.3    |
   | VERSION          | ICAL:version          | Appendix A # 3.7.4    |
   | ATTACH           | ICAL:attach           | Appendix A # 3.8.1.1  |
   | CATEGORIES       | ICAL:categories       | Appendix A # 3.8.1.2  |
   | CLASS            | ICAL:class            | Appendix A # 3.8.1.3  |
   | COMMENT          | ICAL:comment          | Appendix A # 3.8.1.4  |
   | DESCRIPTION      | ICAL:description      | Appendix A # 3.8.1.5  |
   | GEO              | ICAL:geo              | Appendix A # 3.8.1.6  |



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   | LOCATION         | ICAL:location         | Appendix A # 3.8.1.7  |
   | PERCENT-COMPLETE | ICAL:percent-complete | Appendix A # 3.8.1.8  |
   | PRIORITY         | ICAL:priority         | Appendix A # 3.8.1.9  |
   | RESOURCES        | ICAL:resources        | Appendix A # 3.8.1.10 |
   | STATUS           | ICAL:status           | Appendix A # 3.8.1.11 |
   | SUMMARY          | ICAL:summary          | Appendix A # 3.8.1.12 |
   | COMPLETED        | ICAL:completed        | Appendix A # 3.8.2.1  |
   | DTEND            | ICAL:dtend            | Appendix A # 3.8.2.2  |
   | DUE              | ICAL:due              | Appendix A # 3.8.2.3  |
   | DTSTART          | ICAL:dtstart          | Appendix A # 3.8.2.4  |
   | DURATION         | ICAL:duration         | Appendix A # 3.8.2.5  |
   | FREEBUSY         | ICAL:freebusy         | Appendix A # 3.8.2.6  |
   | TRANSP           | ICAL:transp           | Appendix A # 3.8.2.7  |
   | TZID             | ICAL:tzid             | Appendix A # 3.8.3.1  |
   | TZNAME           | ICAL:tzname           | Appendix A # 3.8.3.2  |
   | TZOFFSETFROM     | ICAL:tzoffsetfrom     | Appendix A # 3.8.3.3  |
   | TZOFFSETTO       | ICAL:tzoffsetto       | Appendix A # 3.8.3.4  |
   | TZURL            | ICAL:tzurl            | Appendix A # 3.8.3.5  |
   | ATTENDEE         | ICAL:attendee         | Appendix A # 3.8.4.1  |
   | CONTACT          | ICAL:contact          | Appendix A # 3.8.4.2  |
   | ORGANIZER        | ICAL:organizer        | Appendix A # 3.8.4.3  |
   | RECURRENCE-ID    | ICAL:recurrence-id    | Appendix A # 3.8.4.4  |
   | RELATED-TO       | ICAL:related-to       | Appendix A # 3.8.4.5  |
   | URL              | ICAL:url              | Appendix A # 3.8.4.6  |
   | UID              | ICAL:uid              | Appendix A # 3.8.4.7  |
   | EXDATE           | ICAL:exdate           | Appendix A # 3.8.5.1  |
   | RDATE            | ICAL:rdate            | Appendix A # 3.8.5.2  |
   | RRULE            | ICAL:rrule            | Appendix A # 3.8.5.3  |
   | ACTION           | ICAL:action           | Appendix A # 3.8.6.1  |
   | REPEAT           | ICAL:repeat           | Appendix A # 3.8.6.2  |
   | TRIGGER          | ICAL:trigger          | Appendix A # 3.8.6.3  |
   | CREATED          | ICAL:created          | Appendix A # 3.8.7.1  |
   | DTSTAMP          | ICAL:dtstamp          | Appendix A # 3.8.7.2  |
   | LAST-MODIFIED    | ICAL:last-modified    | Appendix A # 3.8.7.3  |
   | SEQUENCE         | ICAL:sequence         | Appendix A # 3.8.7.4  |
   | REQUEST-STATUS   | ICAL:request-status   | Appendix A # 3.8.8.3  |
   +------------------+-----------------------+-----------------------+

3.4.1.  Special Cases for Properties

   Some properties in iCalendar can contain "structured" value data.
   This includes lists of "standard" value types, as well as values with
   specific "fields".  In XML, these "structured" values are represented
   as separate XML elements in various ways for ease of processing using
   standard XML tools.






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3.4.1.1.  Multi-valued Properties

   The following iCalendar properties can have values that consist of a
   list of "standard" iCalendar values separated by a specific
   delimiter.  In XML these properties are represented by an XML element
   that contains multiple "value" elements (Section 3.6).

         +------------+-----------------+-----------------------+
         | Property   | XML element     | XML Definition        |
         +------------+-----------------+-----------------------+
         | CATEGORIES | ICAL:categories | Appendix A # 3.8.1.2  |
         | RESOURCES  | ICAL:resources  | Appendix A # 3.8.1.10 |
         | FREEBUSY   | ICAL:freebusy   | Appendix A # 3.8.2.6  |
         | EXDATE     | ICAL:exdate     | Appendix A # 3.8.5.1  |
         | RDATE      | ICAL:rdate      | Appendix A # 3.8.5.2  |
         +------------+-----------------+-----------------------+

3.4.1.2.  GEO Property

   In iCalendar, the GEO property value is defined as a semi-colon
   separated list of two FLOAT values, the first representing latitude
   and the second longitude.

   In XML, the value for the ICAL:geo element is represented by an ICAL:
   value element containing an ICAL:latitude element and an ICAL:
   longitude element, each of which contain text values representing the
   FLOAT values.  See Appendix A # 3.8.1.6.

3.4.1.3.  REQUEST-STATUS Property

   In Icalendar, the REQUEST-STATUS property value is defined as a semi-
   colon separated list of two or three TEXT values.  The first
   represents a code, the second a description, and the third (optional)
   additional data.

   In XML, the value for the ICAL:request-status element is represented
   by an ICAL:value element containing an ICAL:code element, and iCAL:
   description element, and optionally and ICAL:data element, each of
   which contain the corresponding TEXT values.  See Appendix A #
   3.8.8.3.

3.5.  Parameters (RFC5545 section 3.4)

   iCalendar parameters are enclosed in the XML element ICAL:parameters
   which optionally occurs once in each property XML element.

   Each invidivual iCalendar parameter is represented in XML by an
   element of the same name as the iCalendar parameter, but in



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   lowercase.  For example, the PARTSTAT parameter is represented in XML
   by the ICAL:partstat element.

   Example:

     <?xml version="1.0" encoding="utf-8"?>
     <icalendar xmlns="urn:ietf:params:xml:ns:icalendar-2.0">
       <vcalendar>
         ...
         <components>
         ...
           <attendee>
             <parameters>
               <partstat>NEEDS-ACTION</partstat>
             </parameters>
             ...
         </components>
       </vcalendar>
     </icalendar>

   Each parameter contains either text, or one or more child XML
   elements representing iCalendar value types.

      +----------------+---------------------+---------------------+
      | Parameter      | XML element         | XML Definition      |
      +----------------+---------------------+---------------------+
      | ALTREP         | ICAL:altrep         | Appendix A # 3.2.1  |
      | CN             | ICAL:cn             | Appendix A # 3.2.2  |
      | CUTYPE         | ICAL:cutype         | Appendix A # 3.2.3  |
      | DELEGATED-FROM | ICAL:delegated-from | Appendix A # 3.2.4  |
      | DELEGATED-TO   | ICAL:delegated-to   | Appendix A # 3.2.5  |
      | DIR            | ICAL:dir            | Appendix A # 3.2.6  |
      | ENCODING       | ICAL:encoding       | Appendix A # 3.2.7  |
      | FMTTYPE        | ICAL:fmttype        | Appendix A # 3.2.8  |
      | FBTYPE         | ICAL:fbtype         | Appendix A # 3.2.9  |
      | LANGUAGE       | ICAL:language       | Appendix A # 3.2.10 |
      | MEMBER         | ICAL:member         | Appendix A # 3.2.11 |
      | PARTSTAT       | ICAL:partstat       | Appendix A # 3.2.12 |
      | RANGE          | ICAL:range          | Appendix A # 3.2.13 |
      | RELATED        | ICAL:related        | Appendix A # 3.2.14 |
      | RELTYPE        | ICAL:reltype        | Appendix A # 3.2.15 |
      | ROLE           | ICAL:role           | Appendix A # 3.2.16 |
      | RSVP           | ICAL:rsvp           | Appendix A # 3.2.17 |
      | SENT-BY        | ICAL:sent-by        | Appendix A # 3.2.18 |
      | TZID           | ICAL:tzid           | Appendix A # 3.2.19 |
      +----------------+---------------------+---------------------+





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3.5.1.  VALUE parameter

   iCalendar defines a VALUE parameter (Section 3.2.20 of [RFC5545].
   This parameter is not mapped to an XML element.  Instead, the value
   type is handled by having different XML elements for each value, and
   these appear inside of ICAL:property elements.  Thus, when converting
   from iCalendar to XML, any VALUE parameters are skipped.  When
   converting from XML into iCalendar, the appropriate VALUE parameter
   MUST be included in the iCalendar property if the value type is not
   the default value type for that property.

3.6.  Values (RFC5545 section 3.3)

   iCalendar value types are mapped into XML elements with a matching
   name in all lowercase.  In some cases, iCalendar defines "structured"
   values and these are mapped into separate child elements in each
   value element, as described by the simple DTD definitions below.

   Some properties allow for multiple values and these are represented
   by separate matching value XML elements.

3.6.1.  Binary (RFC5545 section 4.3.1)

   Description:  iCalendar BINARY property values are represented by the
      ICAL:binary XML element.  The content of the element is base64
      encoded data.  Whitespace MAY be inserted into the data at any
      point to "wrap" the data to reasonable line lengths.  When
      converting back to iCalendar the whitespace MUST first be removed.

   XML Definition:  Appendix A # 3.3.1

3.6.2.  Boolean  (RFC5545 section 4.3.2)

   Description:  iCalendar BOOLEAN property values are represented by
      the ICAL:boolean XML element.  The content of the element is text
      containing either of "TRUE" or "FALSE".

   XML Definition:  Appendix A # 3.3.2

3.6.3.  Calendar User Address (RFC5545 section 4.3.3)

   Description:  iCalendar CAL-ADDRESS property values are represented
      by the ICAL:cal-address XML element.  The content of the element
      is a URI.







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   XML Definition:  Appendix A # 3.3.3

3.6.4.  Date (RFC5545 section 4.3.4)

   Description:  iCalendar DATE property values are represented by the
      ICAL:date XML element.  The content of the element is the same
      date value specified by RFC5545.

   XML Definition:  Appendix A # 3.3.4

3.6.5.  Date-Time (RFC5545 section 4.3.5)

   Description:  iCalendar DATE-TIME property values are represented by
      the ICAL:date-time XML element.  The content of the element is the
      same date-time value specified by RFC5545.

   XML Definition:  Appendix A # 3.3.5

3.6.6.  Duration (RFC5545 section 4.3.6)

   Description:  iCalendar DURATION property values are represented by
      the ICAL:duration XML element.  The content of the element is the
      same duration value specified by RFC5545.

   XML Definition:  Appendix A # 3.3.6

3.6.7.  Float (RFC5545 section 4.3.7)

   Description:  iCalendar FLOAT property values are represented by the
      ICAL:float XML element.  The content of the element is a text
      representation of a floating point number.

   XML Definition:  Appendix A # 3.3.7

3.6.8.  Integer (RFC5545 section 4.3.8)

   Description:  iCalendar INTEGER property values are represented by
      the ICAL:integer XML element.  The content of the element is a
      text representation of an integer number.

   XML Definition:  Appendix A # 3.3.8

3.6.9.  Period of Time (RFC5545 section 4.3.9)








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   Description:  iCalendar PERIOD property values are represented by the
      ICAL:period XML element.  The content of the element is the same
      period value specified by RFC5545.

   XML Definition:  Appendix A # 3.3.9

3.6.10.  Recurrence Rule (RFC5545 section 4.3.10)

   Description:  iCalendar RECUR property values are represented by the
      ICAL:recur XML element.  The content of the element is child
      elements representing the various components of a recurrence rule.

   XML Definition:  Appendix A # 3.3.10

3.6.11.  Text (RFC5545 section 4.3.11)

   Description:  iCalendar TEXT property values are represented by the
      ICAL:text XML element.  The content of the element is simple text.

   XML Definition:  Appendix A # 3.3.11

3.6.12.  Time (RFC5545 section 4.3.12)

   Description:  iCalendar TIME property values are represented by the
      ICAL:time XML element.  The content of the element is three child
      elements representing the hour, minute and second values in the
      time.  In addition, an XML attribute is used to indicate whether
      the time value represents a UTC based time (represented by a
      trailing "Z" in the iCalendar value).

   XML Definition:  Appendix A # 3.3.12

3.6.13.  URI (RFC5545 section 4.3.13)

   Description:  iCalendar URI property values are represented by the
      ICAL:uri XML element.  The content of the element is a URI.

   XML Definition:  Appendix A # 3.3.13

3.6.14.  UTC Offset (RFC5545 section 4.3.14)

   Description:  iCalendar UTC-OFFSET property values are represented by
      the ICAL:utc-offset XML element.  The content of the element is
      two or three child elements representing the hour, minute and
      (optional) second values in the UTC offset.  In addition, an XML
      attribute is used to indicate whether the offset value represents
      a positive or negative offset.




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   XML Definition:  Appendix A # 3.3.14

3.7.  Extensions

   iCalendar extension properties and parameters (those with an "X-"
   prefix in their name) are handled in the same way as other properties
   and parameters: the property or parameter is represented by an XML
   element with the same name, but in lowercase. e.g., the "X-FOO"
   property in iCalendar turns into the ICAL:x-foo element in XML.

4.  Converting from XML into iCalendar

   When converting component, property and parameter values, the names
   SHOULD be converted to uppercase.  Although iCalendar names are case
   insensitive, common practice is to keep them all uppercase following
   the actual definitions in [RFC5545].

   Backslash escaping and line folding MUST be applied to the resulting
   iCalendar data as required by [RFC5545].

4.1.  Converting XML Extensions into iCalendar

   XML extensions are converted back to iCalendar in one of two ways,
   depending on whether the extensions are in the iCalendar XML
   namespace, or in an external namespace.

   Extensions that are part of the iCalendar XML namespace MUST have
   element names that being with "x-", and will be converted back to the
   equivalent extension property in iCalendar.  For example, the "x-foo"
   element will convert to the "X-FOO" iCalendar property.

   Extensions that are in a namespace other than the iCalendar XML
   namespace SHOULD be preserved in the iCalendar representation using
   the XML iCalendar property described in Section 4.2.

4.2.  The XML property for iCalendar

   This section describes an extension property for iCalendar, as
   covered in section 8.2.3 of [RFC5545].

   Property name: XML

   Purpose: To embed XML-encoded calendar data in the iCalendar format.

   Value type: A single text value.

   Property parameters: None allowed.




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   Conformance: The property can appear on any iCalendar component.

   Description: The value of this property is an XML element.  The XML
   property MUST NOT be used to contain properties that are already
   defined in iCalendar, or properties that use the "X-" iCalendar
   extension property syntax.  Since all elements in the
   urn:ietf:params:xml:ns:icalendar-2.0 namespace convert to a well-
   defined iCalendar object, the elements in this property MUST NOT be
   in the urn:ietf:params:xml:ns:icalendar-2.0 namespace.  The XML
   element which is the value of this property MUST have an XML
   namespace declaration.

   There can be more than one XML property present for a given iCalendar
   object.  The ordering of XML properties is not preserved in the
   conversion between XML and iCalendar.

   Format definition: This property is defined by the following
   notation:

   xml = "XML:" text CRLF

   Example: The following is an example of an iCalendar event with a
   location embedded in KML markup inside the XML property.

   BEGIN:VCALENDAR
   CALSCALE:GREGORIAN
   PRODID:-//Example Inc.//Example Calendar//EN
   VERSION:2.0
   BEGIN:VEVENT
   DTSTAMP:20080205T191224Z
   DTSTART:20081006
   SUMMARY:Planning meeting
   UID:4088E990AD89CB3DBB484909
   XML:<kml xmlns="http://www.opengis.net/kml/2.2">...</kml>
   END:VEVENT
   END:VCALENDAR

5.  Handling link elements in XML and iCal

   Both Atom [RFC4287] and HTML [W3C.REC-html401-19991224] use a link
   element to reference external information which is related in some
   way to the referencing document. iCalendar [RFC5545] does not have
   such a mechanism.

   There are several common use cases where it would be useful for a
   calendar item to link to external structured data.  For instance, it
   would be useful for an event item to denote the location of the event
   by referencing a vCard.  Similarly, there may be a primary contact



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   person for the event, and that person's vCard should be linked from
   the event as well.

   Because this link format is so commonly used in XML documents, this
   section:

   o  Recommends a preferred format for links in xCal documents.

   o  Specifies an iCalendar extension for including links in iCalendar
      documents.

   o  Describes how to convert between the two formats.

5.1.  Links in xCal documents

   It is RECOMMENDED that calendar data in the xCal format use the Atom
   link element (as specified in [RFC5545], section 4.2.7) for linking
   to external related resources.

5.2.  The location relation type

   This section defines the location relation type.

   o  Relation Name: location

   o  Description: Designates a location for the referencing item.
      Typically the location will be in the form of a vCard, but it
      could be some other kind of document containing location
      information.

   o  Reference: This document.

5.3.  The LINK property for iCalendar

   This section describes an extension property for iCalendar, as
   covered in section 8.2.3 of [RFC5545].

   Property name: LINK

   Purpose: To reference external documents related to this calendar
   item

   Value type: A single URI value.

   Property parameters: "rel", "fmttype", "hreflang", "title", and
   "length", to match the attributes allowed on the Atom link element.
   See definitions below.




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   Conformance: The property can appear on any iCalendar component.

   Description: The value of this property is a URI which references an
   external resource related to the component.

   Format definition: This property is defined by the following
   notation:


        link = "LINK" linkparam ":" uri CRLF

        linkparam = *(
                    ;
                    ; The following is OPTIONAL and MUST occur only once
                    ;
                    (";" relparam) /
                    ;
                    ; The following is OPTIONAL and MUST occur only once
                    ;
                    (";" fmttypeparam) /
                    ;
                    ; The following is OPTIONAL and MUST occur only once
                    ;
                    (";" hreflangparam) /
                    ;
                    ; The following is OPTIONAL and MUST occur only once
                    ;
                    (";" titleparam) /
                    ;
                    ; The following is OPTIONAL and MUST occur only once
                    ;
                    (";" lengthparam) /
                    ;
                    ; The following is OPTIONAL and MAY occur
                    ; more than once
                    ;
                    (";" other-param)
                    ;
                    )

         relparam = TBD

         hreflangparam = TBD

         titleparam = TBD

         lengthparam = TBD




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   With the exception of the fmttype paramter, the values allowed for
   the parameters are exactly as specified in section 4.2.7 of
   [RFC5545].

   Example: The following is an example of an iCalendar event with a
   LINK property.

   BEGIN:VCALENDAR
   CALSCALE:GREGORIAN
   PRODID:-//Example Inc.//Example Calendar//EN
   VERSION:2.0
   BEGIN:VEVENT
   DTSTAMP:20080205T191224Z
   DTSTART:20081006
   SUMMARY:Planning meeting
   UID:4088E990AD89CB3DBB484909
   LINK;REL=location:http://example.org/people/samplevcard.vcf
   END:VEVENT
   END:VCALENDAR

5.4.  Converting links between xCal and iCalendar

   Since the LINK parameter is specified in terms of the link element
   defined by [RFC5545], converting between the two is straightforward.
   When converting from iCalendar to xCal, simply take any parameters
   present and assign their values to the corresponding attribute on the
   link element.

   Any unknown extensions either in the iCalendar or xCal format MAY be
   ignored when converting to the other format.

6.  Security Considerations

   This extension does not introduce any new security concerns than
   those already described in iCalendar.

7.  IANA Considerations

   This document defines a new URN to identify a new XML namespace for
   iCalendar data.  The URN conforms to a registry mechanism described
   in [RFC3688].

   This document defines a new media type.  The registration is in
   Section 7.2.

   This document defines a new property for iCalendar.  The registration
   is in Section 4.2.




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7.1.  Namespace Registration

   Registration request for the iCalendar namespace:

   URI: urn:ietf:params:xml:ns:icalendar-2.0

   Registrant Contact: See the "Authors' Addresses" section of this
   document.

   XML: None.  Namespace URIs do not represent an XML specification.

7.2.  Media Type

   This section defines the MIME media type for use with iCalendar in
   XML data.

   To:  ietf-types@iana.org

   Subject:  Registration of media type application/xml+calendar

   Type name:  application

   Subtype name:  xml+calendar

   Required parameters:  none

   Optional parameters:  charset, method, component and optinfo as
      defined for the text/calendar media type

   Encoding considerations:  iCalendar data is typically UTF-8 and thus
      the XML representation will follow that.  As a result, for 7-bit
      transports, data in UTF-8 MUST be encoded in quoted-printable or
      base64.

   Security considerations:  See Section 6.

   Interoperability considerations:  This media type provides an
      alternative syntax to iCalendar data based on XML.

   Published specification:  This specification.

   Applications which use this media type:  Applications that currently
      make use of the text/calendar media type can use this as an
      alternative.







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   Additional information:

      Magic number(s):  None

      File extension(s):  XML data should use "xml" as the file
         extension.

      Macintosh file type code(s):  None specified.

   Person & email address to contact for further information:  See the
      "Author's Address" section of this document.

   Intended usage:  COMMON

   Restrictions on usage:  There are no restrictions on where this media
      type can be used.

   Author:  See the "Author's Address" section of this document.

   Change controller:  IETF

8.  Acknowledgments

   This specification originated from the work of the XML technical
   committee of the Calendaring and Scheduling Consortium.

9.  References

9.1.  Normative References

   [RFC2119]                   Bradner, S., "Key words for use in RFCs
                               to Indicate Requirement Levels", BCP 14,
                               RFC 2119, March 1997.

   [RFC3688]                   Mealling, M., "The IETF XML Registry",
                               BCP 81, RFC 3688, January 2004.

   [RFC4287]                   Nottingham, M., Ed. and R. Sayre, Ed.,
                               "The Atom Syndication Format", RFC 4287,
                               December 2005.

   [RFC5545]                   Desruisseaux, B., "Internet Calendaring
                               and Scheduling Core Object Specification
                               (iCalendar)", RFC 5545, September 2009.

   [W3C.REC-html401-19991224]  Hors, A., Jacobs, I., and D. Raggett,
                               "HTML 4.01 Specification", World Wide Web
                               Consortium Recommendation REC-html401-



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                               19991224, December 1999, <http://
                               www.w3.org/TR/1999/REC-html401-19991224>.

   [W3C.REC-xml-20040204]      Maler, E., Sperberg-McQueen, C., Paoli,
                               J., Yergeau, F., and T. Bray, "Extensible
                               Markup Language (XML) 1.0 (Third
                               Edition)", World Wide Web Consortium
                               FirstEdition REC-xml-20040204,
                               February 2004, <http://www.w3.org/TR/
                               2004/REC-xml-20040204>.

9.2.  Informative References

Appendix A.  Relax NG Schema

   Below is a Relax NG schema for iCalendar in XML.  This schema uses
   the compact notation of Relax NG.  The numeric section numbers given
   in the comments refer to section in [RFC5545].  The ordering of
   elements follows the section ordering of [RFC5545].

   The Relax NG compact notation "?" operator is used to indicate an
   unordered list of items.  However, that operator, as defined, allows
   "mixing" each element that it operates on at any depth within the
   other elements, rather than just allowing "mixing" of siblings only.
   As a result, the schema provided allows certain constructs that are
   not allowed in iCalendar.  Given that there is no sibling-only
   unordered list operator in RelaxNG, this is the best representation
   that can be given.

   # Relax NG Schema for iCalendar in XML

   default namespace = "urn:ietf:params:xml:ns:icalendar-2.0"

   # 3.2 Property Parameters

   # 3.2.1 Alternate Text Representation

   altrepparam = element altrep { value-uri }

   # 3.2.2 Common Name

   cnparam = element cn { text }

   # 3.2.3 Calendar User Type

   cutypeparam = element cutype {
       "INDIVIDUAL" |
       "GROUP" |



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       "RESOURCE" |
       "ROOM" |
       "UNKNOWN"
   }

   # 3.2.4 Delegators

   delfromparam = element delegated-from { value-cal-address+ }

   # 3.2.5 Delegatees

   deltoparam = element delegated-to { value-cal-address+ }

   # 3.2.6 Directory Entry Reference

   dirparam = element dir { value-uri }

   # 3.2.7 Inline Encoding

   encodingparam = element encoding {
       "8BIT" |
       "BASE64"
   }


   # 3.2.8 Format Type

   fmttypeparam = element fmttype { text }

   # 3.2.9 Free/Busy Time Type

   fbtypeparam = element fbtype {
       "FREE" |
       "BUSY" |
       "BUSY-UNAVAILABLE" |
       "BUSY-TENTATIVE"
   }

   # 3.2.10 Language

   languageparam = element language { text }

   # 3.2.11 Group or List Membership

   memberparam = element member { value-cal-address+ }

   # 3.2.12 Participation Status




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   partstatparam = element partstat {
       type-partstat-event |
       type-partstat-todo |
       type-partstat-jour
   }

   type-partstat-event = (
       "NEEDS-ACTION" |
       "ACCEPTED" |
       "DECLINED" |
       "TENTATIVE" |
       "DELEGATED"
   )

   type-partstat-todo = (
       "NEEDS-ACTION" |
       "ACCEPTED" |
       "DECLINED" |
       "TENTATIVE" |
       "DELEGATED" |
       "COMPLETED" |
       "IN-PROCESS"
   )

   type-partstat-jour = (
       "NEEDS-ACTION" |
       "ACCEPTED" |
       "DECLINED"
   )

   # 3.2.13 Recurrence Identifier Range

   rangeparam = element range {
       "THISANDFUTURE"
   }

   # 3.2.14 Alarm Trigger Relationship

   trigrelparam = element related {
       "START" |
       "END"
   }

   # 3.2.15 Relationship Type

   reltypeparam = element reltype {
       "PARENT" |
       "CHILD" |



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       "SIBLING"
   }

   # 3.2.16 Participation Role

   roleparam = element role {
       "CHAIR" |
       "REQ-PARTICIPANT" |
       "OPT-PARTICIPANT" |
       "NON-PARTICIPANT"
   }

   # 3.2.17 RSVP Expectation

   rsvpparam = element rsvp {
       "TRUE" |
       "FALSE"
   }

   # 3.2.18 Sent By

   sentbyparam = element sent-by { value-cal-address }

   # 3.2.19 Time Zone Identifier

   tzidparam = element tzid { text }

   # 3.3 Property Value Data Types

   # 3.3.1 BINARY

   value-binary =  element binary { text }

   # 3.3.2 BOOLEAN

   value-boolean = element boolean {
       ("TRUE" | "FALSE")
   }

   # 3.3.3 CAL-ADDRESS

   value-cal-address = element cal-address { text }

   # 3.3.4 DATE

   value-date = element date {
           text
   }



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   # 3.3.5 DATE-TIME

   value-date-time = element date-time {
           text
   }

   # 3.3.6 DURATION

   value-duration = element duration {
           text
   }

   # 3.3.7 FLOAT

   value-float = element float { text }

   # 3.3.8 INTEGER

   value-integer = element integer { text }

   # 3.3.9 PERIOD

   value-period = element period {
           text
   }

   # 3.3.10 RECUR

   value-recur = element recur {
       type-freq,
       (type-until | type-count)?,
       element interval  { text }?,
       element bysecond  { text }*,
       element byminute  { text }*,
       element byhour    { text }*,
       type-byday*,
       type-bymonthday*,
       type-byyearday*,
       type-byweekno*,
       element bymonth   { text }*,
       type-bysetpos*,
       element wkst { type-weekday }?
   }

   type-freq = element freq {
       "SECONDLY" |
       "MINUTELY" |
       "HOURLY"   |



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       "DAILY"    |
       "WEEKLY"   |
       "MONTHLY"  |
       "YEARLY"
   }

   type-until = element until {
       type-date |
       type-date-time
   }

   type-count = element count { text }

   type-weekday = (
       "SU" |
       "MO" |
       "TU" |
       "WE" |
       "TH" |
       "FR" |
       "SA"
   )

   type-byday = element byday {
       element ordwk {
           text
       }?,
       element weekday { type-weekday }
   }

   type-bymonthday = element bymonthday {
       text
   }

   type-byyearday = element byyearday {
       text
   }

   type-byweekno = element byweekno {
       text
   }

   type-bysetpos = element bysetpos {
       text
   }

   # 3.3.11 TEXT




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   value-text = element text { text }

   # 3.3.12 TIME

   value-time = element time {
       attribute utc  { "yes" | "no" },
       element hour   { text },
       element minute { text },
       element second { text }
   }

   # 3.3.13 URI

   value-uri = element uri { text }

   # 3.3.14 UTC-OFFSET

   value-utc-offset = element utc-offset {
       attribute sign  { "+" | "-" },
       element hour   { text },
       element minute { text },
       element second { text }?
   }


   # 3.4 iCalendar Stream

   start = element icalendar { vcalendar+ }

   # 3.6 Calendar Components

   vcalendar = element vcalendar {
       type-calprops,
       type-component
   }

   type-calprops = element properties {
       property-prodid &
       property-version &
       property-calscale? &
       property-method?
   }

   type-component = element components {
       (
           component-vevent |
           component-vtodo |
           component-vjournal |



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           component-vfreebusy |
           component-vtimezone
       )*
   }

   # 3.6.1 Event Component

   component-vevent = element vevent {
       type-eventprop,
       element components {
           component-valarm+
       }?
   }

   type-eventprop = element properties {
       property-dtstamp &
       property-dtstart &
       property-uid &

       property-class? &
       property-created? &
       property-description? &
       property-geo? &
       property-last-mod? &
       property-location? &
       property-organizer? &
       property-priority? &
       property-seq? &
       property-status-event? &
       property-summary? &
       property-transp? &
       property-url? &
       property-recurid? &

       property-rrule? &

       (property-dtend | property-duration)? &

       property-attach* &
       property-attendee* &
       property-categories* &
       property-comment* &
       property-contact* &
       property-exdate* &
       property-rstatus* &
       property-related* &
       property-resources* &
       property-rdate*



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   }

   # 3.6.2 To-do Component

   component-vtodo = element vtodo {
       type-todoprop,
       element components {
           component-valarm+
       }?
   }

   type-todoprop = element properties {
       property-dtstamp &
       property-uid &

       property-class? &
       property-completed? &
       property-created? &
       property-description? &
       property-geo? &
       property-last-mod? &
       property-location? &
       property-organizer? &
       property-percent? &
       property-priority? &
       property-recurid? &
       property-seq? &
       property-status-todo? &
       property-summary? &
       property-url? &

       property-rrule? &

       (
           (property-dtstart?, property-dtend? ) |
           (property-dtstart, property-duration)?
       ) &

       property-attach* &
       property-attendee* &
       property-categories* &
       property-comment* &
       property-contact* &
       property-exdate* &
       property-rstatus* &
       property-related* &
       property-resources* &
       property-rdate*



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   }

   # 3.6.3 Journal Component

   component-vjournal = element vjournal {
       type-jourprop
   }

   type-jourprop = element properties {
       property-dtstamp &
       property-uid &

       property-class? &
       property-created? &
       property-dtstart? &
       property-last-mod? &
       property-organizer? &
       property-recurid? &
       property-seq? &
       property-status-jour? &
       property-summary? &
       property-url? &

       property-rrule? &

       property-attach* &
       property-attendee* &
       property-categories* &
       property-comment* &
       property-contact* &
       property-description? &
       property-exdate* &
       property-related* &
       property-rdate* &
       property-rstatus*
   }

   # 3.6.4 Free/Busy Component

   component-vfreebusy = element vfreebusy {
       type-fbprop
   }

   type-fbprop = element properties {
       property-dtstamp &
       property-uid &

       property-contact? &



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       property-dtstart? &
       property-dtend? &
       property-duration? &
       property-organizer? &
       property-url? &

       property-attendee* &
       property-comment* &
       property-freebusy* &
       property-rstatus*
   }

   # 3.6.5 Time Zone Component

   component-vtimezone = element vtimezone {
       element properties {
           property-tzid &

           property-last-mod? &
           property-tzuurl?
       },
       element components {
           (component-standard | component-daylight) &
           component-standard* &
           component-daylight*
       }
   }

   component-standard = element standard {
       type-tzprop
   }

   component-daylight = element daylight {
       type-tzprop
   }

   type-tzprop = element properties {
       property-dtstart &
       property-tzoffsetto &
       property-tzoffsetfrom &

       property-rrule? &

       property-comment* &
       property-rdate* &
       property-tzname*
   }




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   # 3.6.6 Alarm Component

   component-valarm = element valarm {
       audioprop | dispprop | emailprop
   }

   type-audioprop = element properties {
       property-action &
       property-trigger &

       (property-duration, property-repeat)? &

       property-attach?
   }

   type-dispprop = element properties {
       property-action &
       property-description &
       property-trigger &
       property-summary &

       property-attendee+ &

       (property-duration, property-repeat)? &

       property-attach*
   }

   type-emailprop = element properties {
       property-action &
       property-description &
       property-trigger &

       (property-duration, property-repeat)?
   }

   # 3.7 Calendar Properties

   # 3.7.1 Calendar Scale

   property-calscale = element calscale {

       element parameters { empty }?,

       element text { "GREGORIAN" }
   }

   # 3.7.2 Method



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   property-method = element method {

       element parameters { empty }?,

       value-text
   }

   # 3.7.3 Product Identifier

   property-prodid = element prodid {

       element parameters { empty }?,

       value-text
   }

   # 3.7.4 Version

   property-version = element version {

       element parameters { empty }?,

       value-text
   }

   # 3.8 Component Properties

   # 3.8.1 Descriptive Component Properties

   # 3.8.1.1 Attachment

   property-attach = element attach {

       element parameters {
           fmttypeparam? &
           encodingparam?
       }?,

       value-uri | value-binary
   }

   # 3.8.1.2 Categories

   property-categories = element categories {

       element parameters {
           languageparam? &
       }?,



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       value-text+
   }

   # 3.8.1.3 Classification

   property-class = element class {

       element parameters { empty }?,

       element text {
           "PUBLIC" |
           "PRIVATE" |
           "CONFIDENTIAL"
       }
   }

   # 3.8.1.4 Comment

   property-comment = element comment {

       element parameters {
           altrepparam? &
           languageparam?
       }?,

       value-text
   }

   # 3.8.1.5 Description

   property-description = element description {

       element parameters {
           altrepparam? &
           languageparam?
       }?,

       value-text
   }

   # 3.8.1.6 Geographic Position

   property-geo = element geo {

       element parameters { empty }?,

       element value {
           element latitude  { text },



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           element longitude { text }
       }
   }

   # 3.8.1.7 Location

   property-location = element location {

       element parameters {
           altrepparam? &
           languageparam?
       }?,

       value-text
   }

   # 3.8.1.8 Percent Complete

   property-percent = element percent-complete {

       element parameters { empty }?,

       value-integer
   }

   # 3.8.1.9 Priority

   property-priority = element priority {

       element parameters { empty }?,

       value-integer
   }

   # 3.8.1.10 Resources

   property-resources = element resources {

       element parameters {
           altrepparam? &
           languageparam?
       }?,

       value-text+
   }

   # 3.8.1.11 Status




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   property-status-event = element status {

       element parameters { empty }?,

       element text {
           "TENTATIVE" |
           "CONFIRMED" |
           "CANCELLED"
       }
   }

   property-status-todo = element status {

       element parameters { empty }?,

       element text {
           "NEEDS-ACTION" |
           "COMPLETED" |
           "IN-PROCESS" |
           "CANCELLED"
       }
   }

   property-status-jour = element status {

       element parameters { empty }?,

       element text {
           "DRAFT" |
           "FINAL" |
           "CANCELLED"
       }
   }

   # 3.8.1.12 Summary

   property-summary = element summary {

       element parameters {
           altrepparam? &
           languageparam?
       }?,

       value-text
   }

   # 3.8.2 Date and Time Component Properties




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   # 3.8.2.1 Date/Time Completed

   property-completed = element completed {

       element parameters { empty }?,

       value-date-time
   }

   # 3.8.2.2 Date/Time End

   property-dtend = element dtend {

       element parameters {
           tzidparam?
       }?,

       value-date-time |
       value-date
   }

   # 3.8.2.3 Date/Time Due

   property-due = element due {

       element parameters {
           tzidparam?
       }?,

       value-date-time |
       value-date
   }

   # 3.8.2.4 Date/Time Start

   property-dtstart = element dtstart {

       element parameters {
           tzidparam?
       }?,

       value-date-time |
       value-date
   }

   # 3.8.2.5 Duration

   property-duration = element duration {



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       element parameters { empty }?,

       value-duration
   }

   # 3.8.2.6 Free/Busy Time

   property-freebusy = element freebusy {

       element parameters {
           fbtypeparam?
       }?,


       value-period+
   }

   # 3.8.2.7 Time Transparency

   property-transp = element transp {

       element parameters { empty }?,

       element text {
           "OPAQUE" |
           "TRANSPARENT"
       }
   }

   # 3.8.3 Time Zone Component Properties

   # 3.8.3.1 Time Zone Identifier

   property-tzid = element tzid {

       element parameters { empty }?,

       value-text
   }

   # 3.8.3.2 Time Zone Name

   property-tzname = element tzname {

       element parameters {
           languageparam?
       }?,




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       value-text
   }

   # 3.8.3.3 Time Zone Offset From

   property-tzoffsetfrom = element tzoffsetfrom {

       element parameters { empty }?,

       value-utc-offset
   }

   # 3.8.3.4 Time Zone Offset To

   property-tzoffsetto = element tzoffsetto {

       element parameters { empty }?,

       value-utc-offset
   }

   # 3.8.3.5 Time Zone URL

   property-tzurl = element tzurl {

       element parameters { empty }?,

       value-uri
   }

   # 3.8.4 Relationship Component Properties

   # 3.8.4.1 Attendee

   property-attendee = element attendee {

       element parameters {
           cutypeparam? &
           memberparam? &
           roleparam? &
           partstatparam? &
           rsvpparam? &
           deltoparam? &
           delfromparam? &
           sentbyparam? &
           cnparam? &
           dirparam? &
           languageparam?



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       }?,

       value-cal-address
   }

   # 3.8.4.2 Contact

   property-contact = element contact {

       element parameters {
           altrepparam? &
           languageparam?
       }?,

       value-text
   }

   # 3.8.4.3 Organizer

   property-organizer = element organizer {

       element parameters {
           cnparam? &
           dirparam? &
           sentbyparam? &
           languageparam?
       }?,

       value-cal-address
   }

   # 3.8.4.4 Recurrence ID

   property-recurid = element recurrence-id {

       element parameters {
           tzidparam? &
           rangeparam?
       }?,

       value-date-time |
       value-date
   }

   # 3.8.4.5 Related-To

   property-related = element related-to {




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       element parameters {
           reltypeparam?
       }?,

       value-text
   }

   # 3.8.4.6 Uniform Resource Locator

   property-url = element url {

       element parameters { empty }?,

       value-uri
   }

   # 3.8.4.7 Unique Identifier

   property-uid = element uid {

       element parameters { empty }?,

       value-text
   }

   # 3.8.5 Recurrence Component Properties

   # 3.8.5.1 Exception Date/Times

   property-exdate = element exdate {

       element parameters {
           tzidparam?
       }?,

       value-date-time+ |
       value-date+
   }

   # 3.8.5.2 Recurrence Date/Times

   property-rdate = element rdate {

       element parameters {
           tzidparam?
       }?,

       value-date-time+ |



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       value-date+ |
       value-period+
   }

   # 3.8.5.3 Recurrence Rule

   property-rrule = element rrule {

       element parameters { empty }?,

       value-recur
   }

   # 3.8.6 Alarm Component Properties

   # 3.8.6.1 Action

   property-action = element action {

       element parameters { empty }?,

       element text {
           "AUDIO" |
           "DISPLAY" |
           "EMAIL"
       }
   }

   # 3.8.6.2 Repeat Count

   property-repeat = element repeat {

       element parameters { empty }?,

       value-integer
   }

   # 3.8.6.3 Trigger

   property-repeat = element repeat {

       (
           element parameters {
               trigrelparam?
           }?,

           value-duration
       ) |



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       (
           element parameters { empty }?,

           value-date-time
       )
   }

   # 3.8.7 Change Management Component Properties

   # 3.8.7.1 Date/Time Created

   property-created = element created {

       element parameters { empty }?,

       value-date-time
   }

   # 3.8.7.2 Date/Time Stamp

   property-dtstamp = element dtstamp {

       element parameters { empty }?,

       value-date-time
   }

   # 3.8.7.3 Last Modified

   property-last-mod = element last-modified {

       element parameters { empty }?,

       value-date-time
   }

   # 3.8.7.4 Sequence Number

   property-seq = element sequence {

       element parameters { empty }?,

       value-integer
   }

   # 3.8.8 Miscellaneous Component Properties

   # 3.8.8.3 Request Status



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   property-rstatus = element request-status {

       element parameters {
           languageparam?
       }?,

       element value {
           element code { text },
           element description { text },
           element data { text }?
       }
   }

Appendix B.  XML Stylesheet for conversion to iCalendar

   TO DO

Appendix C.  Example

   Below is some example iCalendar data and its representation in XML as
   defined by this specification.

C.1.  iCalendar Data

   BEGIN:VCALENDAR
   CALSCALE:GREGORIAN
   PRODID:-//Example Inc.//Example Calendar//EN
   VERSION:2.0
   BEGIN:VEVENT
   DTSTAMP:20080205T191224Z
   DTSTART:20081006
   SUMMARY:Planning meeting
   UID:4088E990AD89CB3DBB484909
   END:VEVENT
   END:VCALENDAR
















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C.2.  XML Data

   <?xml version="1.0" encoding="utf-8"?>
   <icalendar xmlns="urn:ietf:params:xml:ns:icalendar-2.0">
    <vcalendar>
     <properties>
      <calscale><text>GREGORIAN</text></calscale>
      <prodid>
       <text>-//Example Inc.//Example Calendar//EN</text>
      </prodid>
      <version><text>2.0</text></version>
     </properties>
     <components>
      <vevent>
       <properties>
        <dtstamp>
         <date-time utc='yes'>
          <year>2008</year><month>2</month><day>5</day>
          <hour>19</hour><minute>12</minute><second>24</second>
         </date-time>
        </dtstamp>
        <dtstart>
         <date>
          <year>2008</year><month>10</month><day>6</day>
         </date>
        </dtstart>
        <summary>
         <text>Planning meeting</text>
        </summary>
        <uid>
         <text>4088E990AD89CB3DBB484909</text>
        </uid>
       </properties>
      </vevent>
     </components>
    </vcalendar>
   </icalendar>

Appendix D.  Change History (to be removed prior to publication as an
             RFC)

   Changes from -00:

   1.  Changed 2445bis references to RFC5545.

   2.  Added a version number to the XML namespace for iCalendar.





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   3.  Changed the values for the date, date-time, period, and duration
       elements to exactly match the values specified in RFC5545.
       Previously these were broken out into separate elements for day,
       month, year, etc.

   4.  Added specification for XML property in iCalendar.

Authors' Addresses

   Cyrus Daboo
   Apple Inc.
   1 Infinite Loop
   Cupertino, CA  95014
   USA

   EMail: cyrus@daboo.name
   URI:   http://www.apple.com/


   Mike Douglass
   Rensselaer Polytechnic Institute
   110 8th Street
   Troy, NY  12180
   USA

   EMail: douglm@rpi.edu
   URI:   http://www.rpi.edu/


   Steven Lees
   Microsoft Corporation
   One Microsoft Way
   Redmond, WA  98052
   USA

   EMail: Steven.Lees@microsoft.com
   URI:   http://www.microsoft.com/














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