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Versions: (draft-jenkins-jscalendar) 00 01

Calendaring extensions                                        N. Jenkins
Internet-Draft                                               R. Stepanek
Intended status: Standards Track                                FastMail
Expires: September 3, 2018                                 March 2, 2018


           JSCalendar: A JSON representation of calendar data
                    draft-ietf-calext-jscalendar-01

Abstract

   This specification defines a data model and JSON representation of
   calendar data that can be used for storage and data exchange in a
   calendaring and scheduling environment.  It aims to be an alternative
   to the widely deployed iCalendar data format and to be unambiguous,
   extendable and simple to process.

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   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."

   This Internet-Draft will expire on September 3, 2018.

Copyright Notice

   Copyright (c) 2018 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
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   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 Simplified BSD License.



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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
     1.1.  Relation to the iCalendar format  . . . . . . . . . . . .   4
     1.2.  Notational Conventions  . . . . . . . . . . . . . . . . .   5
   2.  JSCalendar objects  . . . . . . . . . . . . . . . . . . . . .   5
     2.1.  JSEvent . . . . . . . . . . . . . . . . . . . . . . . . .   5
     2.2.  JSTask  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     2.3.  JSGroup . . . . . . . . . . . . . . . . . . . . . . . . .   6
   3.  Structure of JSCalendar objects . . . . . . . . . . . . . . .   6
     3.1.  Type signatures . . . . . . . . . . . . . . . . . . . . .   6
     3.2.  Data Types  . . . . . . . . . . . . . . . . . . . . . . .   6
       3.2.1.  UTCDate . . . . . . . . . . . . . . . . . . . . . . .   7
       3.2.2.  LocalDate . . . . . . . . . . . . . . . . . . . . . .   7
       3.2.3.  Duration  . . . . . . . . . . . . . . . . . . . . . .   7
       3.2.4.  PatchObject . . . . . . . . . . . . . . . . . . . . .   7
       3.2.5.  Normalisation and equivalence . . . . . . . . . . . .   8
     3.3.  Custom property extensions and values . . . . . . . . . .   9
   4.  Common JSCalendar properties  . . . . . . . . . . . . . . . .   9
     4.1.  Metadata properties . . . . . . . . . . . . . . . . . . .   9
       4.1.1.  @type . . . . . . . . . . . . . . . . . . . . . . . .   9
       4.1.2.  uid . . . . . . . . . . . . . . . . . . . . . . . . .  10
       4.1.3.  relatedTo . . . . . . . . . . . . . . . . . . . . . .  10
       4.1.4.  prodId  . . . . . . . . . . . . . . . . . . . . . . .  11
       4.1.5.  created . . . . . . . . . . . . . . . . . . . . . . .  11
       4.1.6.  updated . . . . . . . . . . . . . . . . . . . . . . .  11
       4.1.7.  sequence  . . . . . . . . . . . . . . . . . . . . . .  11
       4.1.8.  method  . . . . . . . . . . . . . . . . . . . . . . .  11
     4.2.  What and where properties . . . . . . . . . . . . . . . .  11
       4.2.1.  title . . . . . . . . . . . . . . . . . . . . . . . .  12
       4.2.2.  description . . . . . . . . . . . . . . . . . . . . .  12
       4.2.3.  htmlDescription . . . . . . . . . . . . . . . . . . .  12
       4.2.4.  locations . . . . . . . . . . . . . . . . . . . . . .  12
       4.2.5.  links . . . . . . . . . . . . . . . . . . . . . . . .  14
       4.2.6.  locale  . . . . . . . . . . . . . . . . . . . . . . .  15
       4.2.7.  keywords  . . . . . . . . . . . . . . . . . . . . . .  15
       4.2.8.  categories  . . . . . . . . . . . . . . . . . . . . .  16
       4.2.9.  color . . . . . . . . . . . . . . . . . . . . . . . .  16
     4.3.  Recurrence properties . . . . . . . . . . . . . . . . . .  16
       4.3.1.  recurrenceRule  . . . . . . . . . . . . . . . . . . .  16
       4.3.2.  recurrenceOverrides . . . . . . . . . . . . . . . . .  18
     4.4.  Sharing and scheduling properties . . . . . . . . . . . .  19
       4.4.1.  priority  . . . . . . . . . . . . . . . . . . . . . .  19
       4.4.2.  freeBusyStatus  . . . . . . . . . . . . . . . . . . .  19
       4.4.3.  privacy . . . . . . . . . . . . . . . . . . . . . . .  20
       4.4.4.  replyTo . . . . . . . . . . . . . . . . . . . . . . .  21
       4.4.5.  participants  . . . . . . . . . . . . . . . . . . . .  22
     4.5.  Alerts properties . . . . . . . . . . . . . . . . . . . .  25



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       4.5.1.  useDefaultAlerts  . . . . . . . . . . . . . . . . . .  25
       4.5.2.  alerts  . . . . . . . . . . . . . . . . . . . . . . .  25
     4.6.  Multilingual properties . . . . . . . . . . . . . . . . .  28
       4.6.1.  localizations . . . . . . . . . . . . . . . . . . . .  28
   5.  Type-specific JSCalendar properties . . . . . . . . . . . . .  29
     5.1.  JSEvent properties  . . . . . . . . . . . . . . . . . . .  29
       5.1.1.  start . . . . . . . . . . . . . . . . . . . . . . . .  29
       5.1.2.  timeZone  . . . . . . . . . . . . . . . . . . . . . .  29
       5.1.3.  duration  . . . . . . . . . . . . . . . . . . . . . .  29
       5.1.4.  isAllDay  . . . . . . . . . . . . . . . . . . . . . .  29
       5.1.5.  status  . . . . . . . . . . . . . . . . . . . . . . .  30
     5.2.  JSTask properties . . . . . . . . . . . . . . . . . . . .  30
       5.2.1.  due . . . . . . . . . . . . . . . . . . . . . . . . .  30
       5.2.2.  start . . . . . . . . . . . . . . . . . . . . . . . .  30
       5.2.3.  timeZone  . . . . . . . . . . . . . . . . . . . . . .  30
       5.2.4.  estimatedDuration . . . . . . . . . . . . . . . . . .  31
       5.2.5.  completed . . . . . . . . . . . . . . . . . . . . . .  31
       5.2.6.  isAllDay  . . . . . . . . . . . . . . . . . . . . . .  31
       5.2.7.  progress  . . . . . . . . . . . . . . . . . . . . . .  31
       5.2.8.  status  . . . . . . . . . . . . . . . . . . . . . . .  32
     5.3.  JSGroup properties  . . . . . . . . . . . . . . . . . . .  32
       5.3.1.  entries . . . . . . . . . . . . . . . . . . . . . . .  33
       5.3.2.  source  . . . . . . . . . . . . . . . . . . . . . . .  33
   6.  Conversion from and to iCalendar  . . . . . . . . . . . . . .  33
     6.1.  JSEvent . . . . . . . . . . . . . . . . . . . . . . . . .  33
     6.2.  JSTask  . . . . . . . . . . . . . . . . . . . . . . . . .  34
     6.3.  JSGroup . . . . . . . . . . . . . . . . . . . . . . . . .  35
     6.4.  Common properties . . . . . . . . . . . . . . . . . . . .  36
     6.5.  Locations and participants  . . . . . . . . . . . . . . .  38
     6.6.  Unknown properties  . . . . . . . . . . . . . . . . . . .  40
   7.  JSCalendar object examples  . . . . . . . . . . . . . . . . .  40
     7.1.  Simple event  . . . . . . . . . . . . . . . . . . . . . .  40
     7.2.  Simple task . . . . . . . . . . . . . . . . . . . . . . .  41
     7.3.  Simple group  . . . . . . . . . . . . . . . . . . . . . .  41
     7.4.  All-day event . . . . . . . . . . . . . . . . . . . . . .  42
     7.5.  Task with a due date  . . . . . . . . . . . . . . . . . .  42
     7.6.  Event with end time-zone  . . . . . . . . . . . . . . . .  43
     7.7.  Floating-time event (with recurrence) . . . . . . . . . .  43
     7.8.  Event with multiple locations and localization  . . . . .  44
     7.9.  Recurring event with overrides  . . . . . . . . . . . . .  45
     7.10. Recurring event with participants . . . . . . . . . . . .  46
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  47
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  47
   10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  47
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  47
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  47
     11.2.  Informative References . . . . . . . . . . . . . . . . .  50
     11.3.  URIs . . . . . . . . . . . . . . . . . . . . . . . . . .  50



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   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  50

1.  Introduction

   This document defines a data model for calendar event and task
   objects, or groups of such objects, in electronic calendar
   applications and systems.  It aims to be unambiguous, extendable and
   simple to process.

   The key design considerations for this data model are as follows:

   o  The attributes of the calendar entry represented must be described
      as a simple key-value pair, reducing complexity of its
      representation.

   o  The data model should avoid all ambiguities and make it difficult
      to make mistakes during implementation.

   o  Most of the initial set of attributes should be taken from the
      iCalendar data format ([RFC5545], also see Section 1.1), but the
      specification should add new attributes or value types, or not
      support existing ones, where appropriate.  Conversion between the
      data formats need not fully preserve semantic meaning.

   o  Extensions, such as new properties and components, MUST NOT lead
      to requiring an update to this document.

   The representation of this data model is defined in the I-JSON format
   [RFC7493], which is a strict subset of the JavaScript Object Notation
   (JSON) Data Interchange Format [RFC8259].  Using JSON mostly is a
   pragmatic choice: its widespread use should help to speed up
   JSCalendar adoption and a wide range of production-ready JSON
   implementations allows to decrease interoperability issues.

1.1.  Relation to the iCalendar format

   The iCalendar data format [RFC5545], a widely deployed interchange
   format for calendaring and scheduling data, has served calendaring
   vendors for a long while, but contains some ambiguities and pitfalls
   that can not be overcome without backward-incompatible changes.

   For example, iCalendar defines various formats for local times, UTC
   time and dates, which confuses new users.  Other sources for errors
   are the requirement for custom time-zone definitions within a single
   calendar component, as well as the iCalendar format itself; the
   latter causing interoperability issues due to misuse of CR LF
   terminated strings, line continuations and subtle differences between
   iCalendar parsers.  Lastly, up until recently the iCalendar format



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   did not allow to express the difference between two calendar
   components, which results in verbose exchanges during scheduling.

   Some of these issues were addressed by the jCal [RFC7265] format,
   which is a direct mapping between iCalendar and JSON.  However, it
   did not attempt to extend or update iCalendar semantics.

1.2.  Notational Conventions

   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].

   The underlying format used for this specification is JSON.
   Consequently, the terms "object" and "array" as well as the four
   primitive types (strings, numbers, booleans, and null) are to be
   interpreted as described in Section 1 of[RFC8259].

   Some examples in this document contain "partial" JSON 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.

2.  JSCalendar objects

   This section describes the calendar object types specified by
   JSCalendar.

2.1.  JSEvent

   MIME type: "application/calendar+json;type=jsevent"

   A JSEvent represents a scheduled amount of time on a calendar,
   typically a meeting, appointment, reminder or anniversary.  Multiple
   participants may partake in the event at multiple locations.

   The @type (Section 4.1.1) property value MUST be "jsevent".

2.2.  JSTask

   MIME type: "application/calendar+json;type=jstask"

   A JSTask represents an action-item, assignment, to-do or work item .

   The @type (Section 4.1.1) property value MUST be "jstask".

   A JSTask may start and be due at certain points in time, may take
   some estimated time to complete and may recur; none of which is



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   required.  This notably differs from JSEvent (Section 2.1) which is
   required to start at a certain point in time and typically takes some
   non-zero duration to complete.

2.3.  JSGroup

   MIME type: "application/calendar+json;type=jsgroup"

   A JSGroup is a collection of JSEvent (Section 2.1) and JSTask
   (Section 2.2) objects.  Typically, objects are grouped by topic (e.g.
   by keywords) or calendar membership.

   The @type (Section 4.1.1) property value MUST be "jsgroup".

3.  Structure of JSCalendar objects

   A JSCalendar object is a JSON object, which MUST be valid I-JSON (a
   stricter subset of JSON), as specified in [RFC8259].  Property names
   and values are case-sensitive.

   The object has a collection of properties, as specified in the
   following sections.  Unless otherwise specified, all properties are
   optional; omitted properties MUST be treated identically to if that
   property had the value of "null", unless otherwise specified.

3.1.  Type signatures

   Types signatures are given for all JSON objects in this document.
   The following conventions are used:

   o  "Boolean|String": The value is either a JSON "Boolean" value, or a
      JSON "String" value.

   o  "Foo": Any name that is not a native JSON type means an object for
      which the properties (and their types) are defined elsewhere
      within this document.

   o  "Foo[]": An array of objects of type "Foo".

   o  "String[Foo]": A JSON "Object" being used as a map (associative
      array), where all the values are of type "Foo".

3.2.  Data Types

   In addition to the standard JSON data types, the following data types
   are used in this specification:





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3.2.1.  UTCDate

   This is a string in [RFC3339] "date-time" format, with the further
   restrictions that any letters MUST be in upper-case, the time
   component MUST be included and the time MUST be in UTC.  Fractional
   second values MUST NOT be included unless non-zero and MUST NOT have
   trailing zeros, to ensure there is only a single representation for
   each date-time.

   For example "2010-10-10T10:10:10.003Z" is OK, but
   "2010-10-10T10:10:10.000Z" is invalid and MUST be encoded as
   "2010-10-10T10:10:10Z".

   In common notation, it should be of the form "YYYY-MM-DDTHH:MM:SSZ".

3.2.2.  LocalDate

   This is a date-time string _with no time-zone/offset information_.
   It is otherwise in the same format as UTCDate: "YYYY-MM-DDTHH:MM:SS".
   The time-zone to associate the LocalDate with comes from an
   associated property, or if no time-zone is associated it defines
   _floating time_. Floating date-times are not tied to any specific
   time-zone.  Instead, they occur in every timezone at the same _wall-
   clock_ time (as opposed to the same instant point in time).

3.2.3.  Duration

   A duration is represented by a subset of ISO8601 duration format, as
   specified by the following ABNF:

       dur-secfrac = "." 1*DIGIT
       dur-second  = 1*DIGIT [dur-secfrac] "S"
       dur-minute  = 1*DIGIT "M" [dur-second]
       dur-hour    = 1*DIGIT "H" [dur-minute]
       dur-time    = "T" (dur-hour / dur-minute / dur-second)
       dur-day     = 1*DIGIT "D"

       duration    = "P" (dur-day [dur-time] / dur-time)

   In addition, the duration MUST NOT include fractional second values
   unless the fraction is non-zero.  A zero duration MUST be represented
   as "P0D".

3.2.4.  PatchObject

   A *PatchObject* is of type "String[*|null]", and represents an
   unordered set of patches on a JSON object.  The keys are a path in a
   subset of [RFC6901] JSON pointer format, with an implicit leading "/"



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   (i.e. prefix each key with "/" before applying the JSON pointer
   evaluation algorithm).

   A patch within a PatchObject is only valid, if all of the following
   conditions apply:

   1.  The pointer MUST NOT reference inside an array (i.e. it MUST NOT
       insert/delete from an array; the array MUST be replaced in its
       entirety instead).

   2.  When evaluating a path, all parts prior to the last (i.e. the
       value after the final slash) MUST exist.

   3.  There MUST NOT be two patches in the PatchObject where the
       pointer of one is the prefix of the pointer of the other, e.g.
       "alerts/1/offset" and "alerts".

   The value associated with each pointer is either:

   o  "null": Remove the property from the patched object.  If not
      present in the parent, this a no-op.

   o  Anything else: The value to replace the inherited property on the
      patch object with (if present) or add to the property (if not
      present).

   Implementations MUST reject a PatchObject if any of its patches are
   invalid.

3.2.5.  Normalisation and equivalence

   JSCalendar aims to provide unambiguous definitions for value types
   and properties, but does not define a general normalisation or
   equivalence method for JSCalendar objects and types.  This is because
   the notion of equivalence might range from byte-level equivalence to
   semantic equivalence, depending on the respective use case (for
   example, the CalDAV protocol [RFC4791] requires octet equivalence of
   the encoded calendar object to determine ETag equivalence).

   Normalisation of JSCalendar objects is hindered because of the
   following reasons:

   o  Custom JSCalendar properties may contain arbitrary JSON values,
      including arrays.  However, equivalence of arrays might or might
      not depend on the order of elements, depending on the respective
      property definition.





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   o  Several JSCalendar property values are defined as URIs and MIME
      types, but normalisation of these types is inherently protocol and
      scheme-specific, depending on the use-case of the equivalence
      definition (see section 6 of [RFC3986]).

   Considering this, the definition of equivalence and normalisation is
   left to client and server implementations and to be negotiated by a
   calendar exchange protocol or defined by another RFC.

3.3.  Custom property extensions and values

   Vendors MAY add additional properties to the calendar object to
   support their custom features.  The names of these properties MUST be
   prefixed with a domain name controlled by the vendor to avoid
   conflict, e.g. "example.com/customprop".

   Some JSCalendar properties allow vendor-specific value extensions.
   If so, vendor specific values MUST be prefixed with a domain name
   controlled by the vendor, e.g. "example.com/customrel", unless
   otherwise noted.

4.  Common JSCalendar properties

   This section describes the properties that are common to the various
   JSCalendar object types.  Specific JSCalendar object types may only
   support a subset of these properties.  The object type definitions in
   section Section 5 describe the set of supported properties per type.

4.1.  Metadata properties

4.1.1.  @type

   Type: "String"

   Specifies the type which this object represents.  This MUST be one of
   the following values, registered in a future RFC, or a vendor-
   specific value:

   o  "jsevent": a JSCalendar event (Section 2.1).

   o  "jstask": a JSCalendar task (Section 2.2).

   o  "jsgroup": a JSCalendar group (Section 2.3).

   A valid JSCalendar object MUST include this property.






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4.1.2.  uid

   Type: "String"

   A globally unique identifier, used to associate the object as the
   same across different systems, calendars and views.  The value of
   this property MUST be unique across _all_ JSCalendar objects, even if
   they are of different type.  [RFC4122] describes a range of
   established algorithms to generate universally unique identifiers
   (UUID), and the random or pseudo-random version is recommended to
   use.

   A valid JSCalendar object MUST include this property.

4.1.3.  relatedTo

   Type: "String[Relation]|null"

   Relates the object to other JSCalendar objects.  This is represented
   as a map of the uids of the related objects to information about the
   relation.

   A *Relation* object has the following properties:

   o  *relation*: "String[]" Describes how the linked object is related
      to this object.

      The strings in the array MUST each be at most one of the following
      values, registered in a future RFC, or a vendor-specific value:

      *  "first": The linked object is the first in the series this
         object is part of.

      *  "next": The linked object is the next in the series this object
         is part of.

      *  "child": The linked object is a subpart of this object.

      *  "parent": This object is part of the overall linked object.

   If an object is split to make a "this and future" change to a
   recurrence, the original object MUST be truncated to end at the
   previous occurrence before this split, and a new object created to
   represent all the objects after the split.  A "relation=["next"]"
   relatedTo property MUST be set on the original object with the uid of
   the new object.  A "relation=["first"]" relatedTo property with the
   UID of the first object in the series MUST be set on the new object.




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   Clients can then follow these UIDs to get the complete set of objects
   if the user wishes to modify them all at once.

4.1.4.  prodId

   Type: "String|null"

   The identifier for the product that created the JSCalendar object.

   The vendor of the implementation SHOULD ensure that this is a
   globally unique identifier, using some technique such as an FPI
   value, as defined in [ISO.9070.1991].

   This property SHOULD NOT be used to alter the interpretation of an
   JSCalendar object beyond the semantics specified in this document.
   For example, it is not to be used to further the understanding of
   non-standard properties.

4.1.5.  created

   Type: "UTCDate|null"

   The date and time this object was initially created.

4.1.6.  updated

   Type: "UTCDate"

   The date and time the data in this object was last modified.

4.1.7.  sequence

   Type: "Number" (Defaults to "0" if omitted)

   Initially zero, this MUST be a non-negative integer that is
   monotonically incremented each time a change is made to the object.

4.1.8.  method

   Type: "String|null"

   The iTIP ([RFC5546]) method, in lower-case.  Used for scheduling.

4.2.  What and where properties







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4.2.1.  title

   Type: "String" (Defaults to the empty string if omitted)

   A short summary of the object.

4.2.2.  description

   Type: "String" (Defaults to the empty string if omitted)

   A longer form description of the object.  This is plain text, but a
   client SHOULD attempt to hyperlink URLs when displaying it.

4.2.3.  htmlDescription

   Type: "String" (Defaults to the empty string if omitted)

   A longer form rich-text description of the object.  This is HTML text
   [1] and allows to reference resources in the *links* property by use
   of CID URLs (see [RFC2392]).  To convert a CID URL to the *cid*
   property value of a *Link* object, implementations MUST follow the
   conversion described in section 2 of [RFC2392].  Implementations MAY
   choose not to follow untrusted external CID URLs referenced in the
   *links* property, in which case they MUST treat the *htmlDescription*
   property as if omitted.  Implementations MUST preserve the value of
   this property, even if it contains untrusted links.

4.2.4.  locations

   Type: "String[Location]|null"

   A map of location ids to Location objects, representing locations
   associated with the object.  A location id may be any string and need
   only be unique to this object, although a UUID is a practical choice.

   A *Location* object has the following properties.  All properties are
   optional, but every Location object MUST have at least one property:

   o  *name*: "String" The human-readable name of the location.

   o  *description*: "String" Human-readable instructions for accessing
      this location.  This may be an address, set of directions, door
      access code, etc.

   o  *rel*: "String" The relation type of this location to the
      JSCalendar object.





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      This MUST be either one of the following values, registered in a
      future RFC, or a vendor-specific value.  Any value the client or
      server doesn't understand should be treated the same as "unknown".

      *  "start": The JSCalendar object starts at this location.

      *  "end": The JSCalendar object ends at this location.

      *  "virtual": This is not a physical location (e.g. this location
         is an online chat room where people will meet).

      *  "unknown": The relation of this location to the calendar object
         is unknown.

   o  *features*: "String[]|null" The features supported by this
      location.

      The strings in the array MUST each be either one of the following
      values, registered in a future RFC, or a vendor-specific value.
      Any value the client or server doesn't understand should be
      ignored, but preserved.

      The features supported by locations with rel-type "virtual" are:

      *  "audio": audio conferencing

      *  "chat": chat or instant messaging

      *  "screen": screen sharing

      *  "video": video conferencing

      *  any vendor-prefixed custom value

   o  *timeZone*: "String|null" (Defaults to "null" if omitted) A time-
      zone for this location.

      If "null", the *timeZone* from the JSCalendar object MUST be
      presumed when a time-zone is needed in relation to this location.

   o  *coordinates*: "String" An [RFC5870] "geo:" URI for the location.

   o  *uri*: "String" A URI that represents how to connect to this
      location.

      This may be a telephone number (represented as
      "tel:+1-555-555-555") for a teleconference, a web address for
      online chat, or any custom URI.



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   o  *linkIds*: "String[]|null" A list of ids for links to alternate
      representations of this location.

      For example, an alternative representation could be in vCard
      format.  If a given value does not correspond to any link id in
      the links property of the instance, this MUST be ignored.

4.2.5.  links

   Type: "String[Link]|null"

   A map of link ids to Link objects, representing external resources
   associated with the object.  A link id may be any string and need
   only be unique to this object, although the href or a UUID are
   practical choices.

   A *Link* object has the following properties:

   o  *href*: "String" A URI from which the resource may be fetched.

      This MAY be a "data:" URL, but it is recommended that the file be
      hosted on a server to avoid embedding arbitrary large data in
      JSCalendar object instances.

   o  *cid* "String|null" The id used within the *htmlDescription*
      property to reference this link.

      If not null, this MUST be a valid Content-ID MIME header value
      (see [RFC2392]).  The identifier MUST be unique within this
      JSCalendar object but has no meaning beyond that.  Specifically,
      it MAY be different from the *Link* object identifier in the
      enclosing *links* property.

   o  *type*: "String|null"(optional, defaults to "null") The content-
      type [RFC6838] of the resource, if known.

   o  *size*: "Number|null"(optional, defaults to "null") The size, in
      bytes, of the resource when fully decoded (i.e. the number of
      bytes in the file the user would download), if known.

   o  *rel*: "String"(optional, defaults to "related") Identifies the
      relation of the linked resource to the object.  The value MUST be
      a registered relation type (see [RFC8288] and IANA Link Relations
      [2]).

      Links with a rel of "enclosure" SHOULD be considered by the client
      as attachments for download.




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      Links with a rel of "describedby" SHOULD be considered by the
      client to be an alternate representation of the description and
      HTML description.

      Links with a rel of "icon" SHOULD be considered by the client to
      be an image that it MAY use when presenting the calendar data to a
      user.  The *properties* object of this link MAY include a
      "display" property indicating the intended purpose of this image.
      If included, the value MUST be either one of the following values,
      registered in a future RFC, or a vendor-specific value.

      *  "badge": an image inline with the title of the object

      *  "graphic": a full image replacement for the object itself

      *  "fullsize": an image that is used to enhance the object

      *  "thumbnail": a smaller variant of "fullsize " to be used when
         space for the image is constrained

   o  *title*: "String|null"(optional, defaults to "null") A human-
      readable description of the resource.

   o  *properties*: "String[String|null]|null"(optional, defaults to
      "null") Extra metadata submitted by clients about a link.  Server
      implementations MUST preserve these properties.

      The keys are as defined in this document, as defined in a future
      RFC, or URIs that should be owned by the client author to avoid
      conflicts.

4.2.6.  locale

   Type: "String|null"

   The [RFC5646] language tag that best describes the locale used for
   the calendar object, if known.

4.2.7.  keywords

   Type: "String[]|null"

   A list of keywords or tags related to the object.  The values are
   free-form and do not have to follow any particular structure.







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4.2.8.  categories

   Type: "String[]|null"

   Specifies the categories related to the calendar object.  Array
   values MUST be URIs.  In contrast to *keywords*, categories typically
   are structured.

   For example, a vendor owning the domain "example.com" might define
   the categories "http://example.com/categories/sports/american-
   football"" and "http://example.com/categories/music/r-b".

4.2.9.  color

   Type: "String|null"

   Specifies a color clients MAY use when displaying this calendar
   object.  The value is a case-insensitive color name taken from the
   CSS3 set of names, defined in Section 4.3 of W3C.REC-
   css3-color-20110607 [3] or a CSS3 RGB color hex value.

4.3.  Recurrence properties

4.3.1.  recurrenceRule

   Type: "Recurrence"

   Defines a recurrence rule (repeating pattern) for recurring calendar
   objects.

   A *Recurrence* object is a JSON object mapping of a RECUR value type
   in iCalendar, see [RFC5545] and[RFC7529].  Objects recur by applying
   the recurrence rule (and *recurrenceOverrides*) to the *start* date/
   time.  A JSTask (Section 2.2) without a *start* property value recurs
   by its *due* date/time, if defined.

   A Recurrence object has the following properties:

   o  *frequency*: "String" This MUST be one of the following values:

      *  "yearly"

      *  "monthly"

      *  "weekly"

      *  "daily"




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      *  "hourly"

      *  "minutely"

      *  "secondly"

      To convert from iCalendar, simply lower-case the FREQ part.

   o  *interval*: "Number"(optional, defaults to "1") The INTERVAL part
      from iCal.  If included, it MUST be an integer "x >= 1".

   o  *rscale*: "String"(optional, defaults to ""gregorian"") The RSCALE
      part from iCalendar RSCALE [RFC7529], converted to lower-case.

   o  *skip*: "String"(optional, defaults to ""omit"") The SKIP part
      from iCalendar RSCALE [RFC7529], converted to lower-case.

   o  *firstDayOfWeek*: "String"(optional, defaults to ""mo"") The WKST
      part from iCalendar, represented as a lower-case abbreviated two-
      letter English day of the week.  If included, it MUST be one of
      the following values: ""mo"|"tu"|"we"|"th"|"fr"|"sa"|"su"".

   o  *byDay*: "NDay[]"(optional) An *NDay* object has the following
      properties:

      *  *day*: "String" The day-of-the-week part of the BYDAY value in
         iCalendar, lower-cased.  MUST be one of the following values:
         ""mo"|"tu"|"we"|"th"|"fr"|"sa"|"su"".

      *  *nthOfPeriod*: "Number"(optional) The optional ordinal part of
         the BYDAY value in iCalendar (e.g. ""+1"" or ""-3"").  If
         present, rather than representing every occurrence of the
         weekday defined in the *day* property of this *NDay*, it
         represents only a specific instance within the recurrence
         period.  The value can be positive or negative, but MUST NOT be
         zero.  A negative integer means nth-last of period.

   o  *byMonthDay*: "Number[]"(optional) The BYMONTHDAY part from
      iCalendar.  The array MUST have at least one entry if included.

   o  *byMonth*: "String[]"(optional) The BYMONTH part from iCalendar.
      Each entry is a string representation of a number, starting from
      "1" for the first month in the calendar (e.g. ""1" " means
      ""January"" with Gregorian calendar), with an optional ""L""
      suffix (see [RFC7529]) for leap months (this MUST be upper-case,
      e.g. ""3L"").  The array MUST have at least one entry if included.





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   o  *byYearDay*: "Number[]"(optional) The BYYEARDAY part from
      iCalendar.  The array MUST have at least one entry if included.

   o  *byWeekNo*: "Number[]"(optional) The BYWEEKNO part from iCalendar.
      The array MUST have at least one entry if included.

   o  *byHour*: "Number[]"(optional) The BYHOUR part from iCalendar.
      The array MUST have at least one entry if included.

   o  *byMinute*: "Number[]"(optional) The BYMINUTE part from iCalendar.
      The array MUST have at least one entry if included.

   o  *bySecond*: "Number[]"(optional) The BYSECOND part from iCalendar.
      The array MUST have at least one entry if included.

   o  *bySetPosition*: "Number[]"(optional) The BYSETPOS part from
      iCalendar.  The array MUST have at least one entry if included.

   o  *count*: "Number"(optional) The COUNT part from iCalendar.  This
      MUST NOT be included if an *until* property is specified.

   o  *until*: "LocalDate"(optional) The UNTIL part from iCalendar.
      This MUST NOT be included if a *count* property is specified.
      Note, as in iCalendar, this date is presumed to be in the time-
      zone specified in *timeZone*. It is not a UTC time.

4.3.2.  recurrenceOverrides

   Type: "LocalDate[PatchObject|null]|null"

   A map of the recurrence-ids (the date-time of the start of the
   occurrence) to either "null", to indicate the occurrence should be
   deleted, or an object of patches to apply to the generated occurrence
   object.

   If the recurrence-id does not match an expanded start date from a
   recurrence rule, it is to be treated as an additional occurrence
   (like an RDATE from iCalendar).  The patch object may often be empty
   in this case.

   By default, an occurrence inherits all properties from the main
   object except the start (or due) date-time, which is shifted to the
   new start time.  However, individual properties of the occurrence can
   be modified by a patch, or multiple patches.

   A pointer in the PatchObject MUST NOT start with one of the following
   prefixes; any patch with such a key MUST be ignored:




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   o  @type

   o  uid

   o  relatedTo

   o  prodId

   o  method

   o  isAllDay

   o  recurrenceRule

   o  recurrenceOverrides

   o  replyTo

4.4.  Sharing and scheduling properties

4.4.1.  priority

   Type: "Number"(defaults to "0" if omitted)

   Specifies a priority for the calendar object.  This may be used as
   part of scheduling systems to help resolve conflicts for a time
   period.

   The priority is specified as an integer in the range 0 to 9.  A value
   of 0 specifies an undefined priority.  A value of 1 is the highest
   priority.  A value of 2 is the second highest priority.  Subsequent
   numbers specify a decreasing ordinal priority.  A value of 9 is the
   lowest priority.  Other integer values are reserved for future use.

4.4.2.  freeBusyStatus

   Type: "String"(defaults to "busy" if omitted)

   Specifies how this property should be treated when calculating free-
   busy state.  The value MUST be one of:

   o  ""free"": The object should be ignored when calculating whether
      the user is busy.

   o  ""busy"": The object should be included when calculating whether
      the user is busy.





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4.4.3.  privacy

   Type: "String"(defaults to "public" if omitted)

   Calendar objects are normally collected together and may be shared
   with other users.  The privacy property allows the object owner to
   indicate that it should not be shared, or should only have the time
   information shared but the details withheld.  Enforcement of the
   restrictions indicated by this property are up to the
   implementations.

   This property MUST NOT affect the information sent to scheduled
   participants; it is only interpreted when the object is shared as
   part of a shared calendar.

   The value MUST be either one of the following values, registered in a
   future RFC, or a vendor-specific value.  Vendor specific values MUST
   be prefixed with a domain name controlled by the vendor, e.g.
   "example.com/topsecret".  Any value the client or server doesn't
   understand should be preserved but treated as equivalent to
   "private".

   o  "public": The full details of the object are visible to those whom
      the object's calendar is shared with.

   o  "private": The details of the object are hidden; only the basic
      time and metadata is shared.  Implementations MUST ensure the
      following properties are stripped when the object is accessed by a
      sharee:

      *  title

      *  description

      *  htmlDescription

      *  locations

      *  links

      *  locale

      *  localizations

      *  participants

      *  replyTo




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      In addition, any patches in "recurrenceOverrides" whose key is
      prefixed with one of the above properties MUST be stripped.

   o  "secret": The object is hidden completely (as though it did not
      exist) when the calendar is shared.

4.4.4.  replyTo

   Type: "String[String]|null"

   Represents methods by which a participant may RSVP to the organizer
   of the calendar object.  The keys in the property value are the
   available methods.  The value is a URI to use that method.  Future
   methods may be defined in future specifications; a calendar client
   MUST ignore any method it does not understand.

   The following methods are defined:

   o  "imip": The organizer accepts an iMIP [RFC6047] response.  The
      value MUST be a "mailto:" URI.

   o  "web": There is a web page where the user may submit an RSVP using
      their browser.  The value MUST be an "http:" or "https:" URI
      Template ([RFC6570]) in level 1 format.  The template MAY contain
      variables that MUST be expanded from the JSCalendar object as
      defined in table Table 1.  Calendar clients SHOULD be prepared to
      handle authentication requests from the respective web page and
      for the participant email, but this specification does not mandate
      any specific mechanism.






















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   +--------------+----------------------------------------------------+
   | Variable     | Expand to                                          |
   +--------------+----------------------------------------------------+
   | email        | The *email* property value of the replying         |
   |              | *Participant* object.                              |
   |              |                                                    |
   | uid          | The *uid* property value of the JSCalendar object. |
   |              |                                                    |
   | sequence     | The *sequence* property value of the JSCalendar    |
   |              | object.                                            |
   |              |                                                    |
   | recurrenceId | The recurrence-id when replying for a single       |
   |              | occurrence of a recurring JSCalendar object. The   |
   |              | value is the date-time of the non-overridden start |
   |              | as determined by expanding the *recurrenceRule* of |
   |              | the JSCalendar object.                             |
   +--------------+----------------------------------------------------+

                  Table 1: replyTo URI Template variables

4.4.5.  participants

   Type: "String[Participant]|null"

   A map of participant ids to participants, describing their
   participation in the calendar object.  A participant id may be any
   string and need only be unique to this calendar object; the email
   address of the participant is a good choice.

   A *Participant* object has the following properties.  Properties are
   mandatory unless marked otherwise:

   o  *name*: "String" The display name of the participant (e.g.  "Joe
      Bloggs").

   o  *email*: "String" The email address for the participant.

   o  *kind*: "String"(optional, defaults to "unknown") What kind of
      entity this participant is.

      This MUST be either one of the following values, registered in a
      future RFC, or a vendor-specific value.  Any value the client or
      server doesn't understand should be treated the same as "unknown".

      *  "individual": a single person

      *  "group": a collection of people invited as a whole




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      *  "resource": a non-human resource, e.g. a projector

      *  "location": a physical location involved in the calendar object
         that needs to be scheduled, e.g. a conference room.

      *  "unknown": no information is available about the kind of this
         participant.

   o  *roles*: "String[]" A list of roles that this participant fulfils.

      At least one value MUST be specified for the participant.  This
      MUST be either one of the following values, registered in a future
      RFC, or a vendor-specific value.  Any value the client or server
      doesn't understand should be preserved but ignored.

      *  "owner": The participant is an owner of the object, and allowed
         to make alterations to any part of it.

      *  "attendee": The participant is an attendee of the calendar
         object.  Attendees are only allowed to alter their own
         participation.

      *  "chair": The participant is in charge of the calendar object
         when it occurs.

   o  *locationId*: "String|null"(optional, defaults to "null") The
      location at which this participant is expected to be attending.

      If the value does not correspond to any location id in the
      locations property of the instance, this MUST be treated the same
      as if the participant's locationId were specified as null.

   o  *rsvpResponse*: "String"(optional, defaults to "needs-action") The
      RSVP response, if any, of this participant.

      The value MUST be either one of the following values, registered
      in a future RFC, or a vendor-specific value:

      *  "needs-action": No status yet set by the participant.

      *  "accepted": The invited participant will participate.

      *  "declined": The invited participant will not participate.

      *  "tentative": The invited participant may participate.

   o  *participation*: "String"(optional, defaults to "required") The
      required participation of this participant.



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      The value MUST be either one of the following values, registered
      in a future RFC, or a vendor-specific value.  Any value the client
      or server doesn't understand should be treated the same as
      "required".

      *  "non-participant": Indicates a participant who is copied for
         information purposes only.

      *  "optional": Indicates a participant whose participation is
         optional.

      *  "required": Indicates a participant whose participation is
         required.

   o  *rsvpWanted*: "Boolean"(optional, defaults to "false") If true,
      the organizer is expecting the participant to notify them of their
      status.

   o  *scheduleSequence*: "Number"(optional, defaults to "0") The
      sequence number of the last response from the participant.  If
      defined, this MUST be a non-negative integer.

      This can be used to determine whether the partcipant has sent a
      new RSVP following significant changes to the calendar object, and
      to determine if future responses are responding to a current or
      older view of the data.

   o  *scheduleUpdated*: "UTCDate|null"(optional, defaults to "null")
      The *updated* property of the last iMIP response from the
      participant.

      This can be compared to the *updated* timestamp in future iMIP
      responses to determine if the response is older or newer than the
      current data.

   o  *invitedBy*: "String|null"(optional, defaults to "null") The
      participant id of the participant who invited this one, if known.

   o  *delegatedTo*: "String[]|null"(optional, defaults to "null") A
      list of participant ids of participants that this participant has
      delegated their participation to.  This MUST be omitted if none
      (rather than an empty array).

   o  *delegatedFrom*: "String[]|null"(optional, defaults to "null") A
      list of participant ids that this participant is acting as a
      delegate for.  This MUST be omitted if none (rather than an empty
      array).




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   o  *memberOf*: "String[]|null"(optional, defaults to "null") A list
      of group participants that were invited to this calendar object,
      which caused this participant to be invited due to their
      membership of the group(s).  This MUST be omitted if none (rather
      than an empty array).

   o  *linkIds*: "String[]|null"(optional, defaults to "null") Links to
      more information about this participant, for example in vCard
      format.  If a given value does not correspond to any link id in
      the links property of the instance, this id MUST be ignored.  This
      MUST be omitted if none (rather than an empty array).

4.5.  Alerts properties

4.5.1.  useDefaultAlerts

   Type: "Boolean" (defaults to "false" if omitted)

   If "true", use the user's default alerts and ignore the value of the
   *alerts* property.  Fetching user defaults is dependent on the API
   from which this JSCalendar object is being fetched, and is not
   defined in this specification.  If an implementation cannot determine
   the user's default alerts, or none are set, it MUST process the
   alerts property as if useDefaultAlerts is set to "false".

4.5.2.  alerts

   Type: "String[Alert]|null"

   A map of alert ids to Alert objects, representing alerts/reminders to
   display or send the user for this calendar object.  An alert id may
   be any string and need only be unique to this calendar object,
   although a globally unique id is a practical choice (also see
   Section 4.1.2)).

   An *Alert* Object has the following properties:

   o  *relativeTo*: "String" (optional, defaults to "before-start")
      Specifies where the offset is relative to for the alarm to
      trigger.  The value MUST be one of:

      *  "before-start"

      *  "after-start"

      *  "before-end"

      *  "after-end"



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   o  *offset*: "Duration" The offset from the start and end/due of the
      calendar object to fire the alert.  If the calendar object does
      not define a time-zone, the user's default time-zone SHOULD be
      used when determining the offset, if known.  Otherwise, the time-
      zone to use is implementation specific.

   o  *action*: "DisplayAction|EmailAction|UnknownAction"

      Describes how to alert the user.

      A *DisplayAction* means a message (which is service dependent, but
      SHOULD include the title and start or due time of the calendar
      object) SHOULD be shown to the user on any client connected to
      this account at the specified time.  How this message is formatted
      (and any sound or other method of drawing the user's attention) is
      client specific.  It has the following properties:

      *  *type*: "String" The value MUST be "display".

      *  *acknowledged*: "UTCDate|null " (optional)

         When the user has permanently dismissed the alert the client
         MUST set this to the current time in UTC.  Other clients which
         sync this property can then automatically dismiss or suppress
         duplicate alerts (alerts with the same alert id that triggered
         on or before this date-time).

         For a recurring calendar object, the *acknowledged* property of
         the parent object MUST be updated, unless the alert is already
         overridden in *recurrenceOverrides*.

      *  *snoozed*: "UTCDate|null" (optional)

         If the user temporarily dismisses the alert, this is the UTC
         date-time after which it should be reshown.  Clients displaying
         this alert SHOULD hide it if the snoozed property is updated to
         a time in the future.  When that time is reached, the alert
         SHOULD be reshown unless acknowledged is now after the original
         trigger time.

         Setting this property on an instance of a recurring calendar
         object MUST update the alarm on the master object, unless the
         respective instance already is defined in
         "recurrenceOverrides".  It MUST NOT generate an override for
         the sole use of snoozing an alarm.

      *  *mediaLinkIds*: "String[]|null " (optional)




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         A list of link identifiers in the JSCalendar object *links*
         property.  Clients SHOULD play one or more of the link contents
         that are supported by the client implementation and are
         appropriate for the given device and user context.

      An *EmailAction* means an email SHOULD be sent as specified in the
      object at the specified time.  It has the following properties:

      *  *type*: "String" The value MUST be "email".

      *  *to*: "Emailer[]" An array of name/email objects to send the
         alert to.

         An *Emailer* object has the following properties:

         +  name: String The name of the recipient.  If not known,
            clients SHOULD use the empty string.

         +  email: String The email address of the recipient.

      *  *subject*: "String" (optional) The subject to use for the
         email.  If omitted, this is implementation specific, but the
         server SHOULD try to choose an appropriate subject, e.g. by
         including the summary.

      *  *textBody*: "String" (optional) The plain-text body to use for
         the email.  If omitted, the body of the email is implementation
         specific, but the server SHOULD include all pertinent details
         about the calendar object, such as summary, location and start
         time.

      *  *htmlBody*: "String" (optional) The HTML body to use for the
         email, with rich-media content processed as for the
         *htmlDescription* property of the JSCalendar object (see
         Section 4.2.3), e.g. all CID URLs MUST be embedded in the
         generated alert email HTML body, or the *htmlBody* property
         ignored completely.  If the textBody property of this alert
         action is not set, the server SHOULD generate a plain-text
         version from the HTML body and include it in a "multipart/
         alternative" MIME message.

      *  *attachments*: "String[]|null" (optional) A list of link
         identifiers in the JSCalendar object links property.  Included
         attachments SHOULD be embedded in the MIME message with the
         "Content-Disposition" header value set to "attachment" (see
         [RFC2183]).  Implementations MAY refuse to include one or more
         attachments when building an alert email, in which case they




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         MUST ignore the contents of the *attachments* property (e.g.
         they MUST NOT include a subset of attachments).

      An *UnknownAction* object is an object that contains a *type *
      property whose value is not "email" or "string", plus zero or more
      other properties.  This is for compatibility with client
      extensions and future RFCs.  The client or server SHOULD NOT
      trigger any type of alert for action types they do not understand,
      but MUST preserve them.

4.6.  Multilingual properties

4.6.1.  localizations

   Type: "String[PatchObject]|null"

   A map of [RFC5646] language tags to patch objects, which localise the
   calendar object into the locale of the respective language tag.

   See the description of PatchObject (Section 3.2.4) for the structure
   of the PatchObject.  The patches are applied to the top-level object
   and MUST only patch the following properties:

   o  title

   o  description

   o  htmlDescription

   o  keywords

   o  Location name

   o  Location description

   o  Link title

   o  EmailAction alert subject

   o  EmailAction alert textBody

   o  EmailAction alert htmlBody

   o  any Link properties entry except the "display" field

   o  any UnknownAction alert property except the "type" field





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   o  any unknown or vendor-specific property (if not defined otherwise
      in a future RFC or vendor-specific extension).

5.  Type-specific JSCalendar properties

5.1.  JSEvent properties

   In addition to the common JSCalendar object properties (Section 4) a
   JSEvent has the following properties:

5.1.1.  start

   Type: "LocalDate" e.g.  "2015-09-02T00:00:00"

   The date/time the event would start in the event's time-zone.

   A valid JSEvent MUST include this property.

5.1.2.  timeZone

   Type: "String|null"

   The IANA Time Zone Database [4] name for the time-zone the event is
   scheduled in, or "null" for floating time.  If omitted, this MUST be
   presumed to be "null" (i.e. floating time).

5.1.3.  duration

   Type: "Duration", e.g.  "P2DT3H" (Defaults to "P0D" if omitted)

   The zero or positive duration of the event in absolute time (i.e. in
   UTC time; ignoring DST shifts).  To get the end date in the event
   time-zone, convert start into UTC, then add the duration, then
   convert the result into the appropriate time-zone.

   A JSEvent MAY be end in a different time-zone (e.g. a plane flight
   crossing time-zones).  In this case, the JSEvent MUST specify the end
   time-zone in a *location* property value that defines its *rel* to be
   "end" and the end time-zone in its *timeZone* property.

5.1.4.  isAllDay

   Type: "Boolean" (optional, defaults to "false")

   Specifies if the event an all day event, such as a birthday or public
   holiday.

   If *isAllDay* is true, then the following restrictions apply:



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   o  the *start* property MUST have a time component of "T00:00:00".

   o  the *duration* property MUST only include a day component.

   Note that all-day events MAY be bound to a specific time-zone, as
   defined by the *timeZone* property.

5.1.5.  status

   Type: "String"

   The scheduling status (Section 4.4) of a JSEvent defaults to
   "confirmed" if omitted.

   If set, it MUST be one of:

   o  "confirmed": Indicates the event is definite.

   o  "cancelled": Indicates the event is cancelled.

   o  "tentative": Indicates the event is tentative.

5.2.  JSTask properties

   In addition to the common JSCalendar object properties (Section 4) a
   JSTask has the following properties:

5.2.1.  due

   Type: "LocalDate|null" e.g.  "2015-09-02T00:00:00"

   The date/time the task is due in the task's time-zone.

5.2.2.  start

   Type: "LocalDate|null" e.g.  "2015-09-02T00:00:00"

   The date/time the task should start in the task's time-zone.

5.2.3.  timeZone

   Type: "String|null"

   The IANA Time Zone Database name for the time-zone the task is
   scheduled in, or "null" for floating time.  If omitted, this MUST be
   presumed to be "null" (i.e. floating time).





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5.2.4.  estimatedDuration

   Type: "Duration|null", e.g.  "P2DT3H"

   Specifies the estimated positive duration of time the task takes to
   complete.

   If the *start* and *due* properties are set, the estimated duration
   SHOULD be less than or equal to the time interval between these
   properties.

5.2.5.  completed

   Type: "UTCDate|null", e.g.  "2016-06-13T12:00:00Z"

   Specifies the date/time the task was completed.

   If the task is recurring and has future instances, a client may want
   to denote a specific task recurrence as completed but leave other
   instances as uncompleted.  One way to achieve this is by overriding
   the completed property in the task *recurrenceOverrides*.  However,
   this could produce a long list of completion times for regularly
   recurring tasks.  An alternative approach is to split the JSTask into
   a current, single instance of JSTask with this instance completion
   time and a future recurring instance.  Also see the definition of the
   *relatedTo* on splitting.

5.2.6.  isAllDay

   Type: "Boolean" (optional, defaults to "false")

   Specifies if the task is an all day task.

   If *isAllDay* is true, then the *start* and *due* properties MUST
   have a time component of "T00:00:00".  Note that the
   *estimatedDuration* property MAY contain a non-zero time duration.
   All-day tasks MAY be bound to a specific time-zone, as defined by the
   *timeZone* property.

5.2.7.  progress

   In addition to the common properties of a *Participant* object
   (Section 4.4.5), a Participant within a JSTask supports the following
   property:

   o  *progress*: "ParticipantProgress|null" The progress of the
      participant for this task, if known.




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   A *ParticipantProgress* object has the following properties:


   o  *status*: "String" Describes the completion status of the
      participant's progress.

      The value MUST be at most one of the following values, registered
      in a future RFC, or a vendor-specific value:

      *  "completed": The progress of this participant is complete.

      *  "in-process": The progress of this participant is in process.

   o  *timestamp*: "UTCDate" Describes the latest time when the
      participant progress got updated.

5.2.8.  status

   Type: "String"

   The scheduling status (Section 4.4) of a JSTask defaults to "needs-
   action" if omitted.

   If set, it MUST be one of:

   o  "needs-action": Indicates the task needs action.

   o  "completed": Indicates the task is completed.  If this value is
      set, then the timestamp in the *completed* property MUST NOT be
      null.

   o  "in-process": Indicates the task is in process.

   o  "cancelled": Indicates the task is cancelled.

5.3.  JSGroup properties

   JSGroup supports the following JSCalendar properties (Section 4):

   o  @type

   o  uid

   o  created

   o  updated

   o  categories



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   o  keywords

   o  name

   o  description

   o  htmlDescription

   o  color

   o  links

   as well as the following JSGroup-specific properties:

5.3.1.  entries

   Type: "(JSTask|JSEvent)[]|null"

   A list of group members.  The list MAY contain multiple object types
   and implementations MUST ignore entries of unknown type.  The
   property value MUST either be "null" or the list MUST NOT be empty.

5.3.2.  source

   Type: "String|null" (optional, default is "null")

   The source from which updated versions of this group may be retrieved
   from.  If the value is not "null", it MUST be a URI.

6.  Conversion from and to iCalendar

   This section specifies which JSCalendar properties can be mapped from
   and to iCalendar format.  Implementations SHOULD follow these
   conversion guidelines.  Still, JSCalendar does not restrict itself to
   iCalendar and conversion between these two formats MAY be lossy.

6.1.  JSEvent

   The iCalendar counterpart to *JSEvent* is the VEVENT component type
   [RFC5545].  A VEVENT component that is a direct child of a VCALENDAR
   component is equivalent to a standalone JSEvent.  A VEVENT component
   *within* a VEVENT maps to the entries of the JSEvent
   *recurrenceOverrides* property.








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   +----------+--------------------------------------------------------+
   | Property | iCalendar counterpart                                  |
   +----------+--------------------------------------------------------+
   | isAllDay | True, if the type of the DTSTART property in iCalendar |
   |          | is DATE. When translating from JSCalendar the          |
   |          | iCalendar DTSTART property is of DATE value type, if   |
   |          | the *isAllDay* property is set to true and the         |
   |          | *timeZone* property is null.                           |
   |          |                                                        |
   | start    | Corresponds to the DTSTART property in iCalendar. Note |
   |          | that time-zone information is stored separately in     |
   |          | JSEvent.                                               |
   |          |                                                        |
   | timeZone | Corresponds to the TZID part of the DTSTART property   |
   |          | in iCalendar.  If the event has a different end time-  |
   |          | zone to start time-zone, this should be added as a     |
   |          | JSCalendar *location* with just a *timeZone* property  |
   |          | and "rel="end"".                                       |
   |          |                                                        |
   | duration | Corresponds to the DURATION or DSTART+DTEND properties |
   |          | in iCalendar.                                          |
   +----------+--------------------------------------------------------+

            Table 2: Translation between JSEvent and iCalendar

6.2.  JSTask

   The iCalendar counterpart to *JSTask* is the VTODO component type
   [RFC5545].  A VTODO component that is a direct child of a VCALENDAR
   component is equivalent to a standalone JSTask.  A VTODO component
   *within* a master VTODO maps to the entries of the JSTask
   *recurrenceOverrides* property.



















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   +-------------------+-----------------------------------------------+
   | Property          | iCalendar counterpart                         |
   +-------------------+-----------------------------------------------+
   | isAllDay          | True, if the type of the DTSTART property in  |
   |                   | iCalendar is DATE. When translating from      |
   |                   | JSCalendar the iCalendar DTSTART property is  |
   |                   | of DATE value type, if the *isAllDay*         |
   |                   | property is set to true and the *timeZone*    |
   |                   | property is null.                             |
   |                   |                                               |
   | due               | Corresponds to the DUE and DTSTART+DURATION   |
   |                   | properties in iCalendar. When mapping         |
   |                   | iCalendar VTODOs with DTSTART+DURATION, the   |
   |                   | due date is the result of adding DURATION to  |
   |                   | DTSTART in the DTSTART time-zone.             |
   |                   |                                               |
   | start             | Corresponds to the DTSTART property in        |
   |                   | iCalendar.                                    |
   |                   |                                               |
   | timeZone          | Corresponds to the TZID part of the           |
   |                   | DTSTART/DUE properties in iCalendar.  If the  |
   |                   | task has a different end time-zone to start   |
   |                   | or due time-zone, this should be added as a   |
   |                   | JSCalendar *location* with just a *timeZone*  |
   |                   | property and "rel="end"".                     |
   |                   |                                               |
   | estimatedDuration | Corresponds to the ESTIMATED-DURATION         |
   |                   | iCalendar property.  *NON-STANDARD*: this     |
   |                   | property is currently non-standard, see       |
   |                   | [draft-apthorp-ical-tasks].                   |
   |                   |                                               |
   | completed         | Maps to the COMPLETED iCalendar property.     |
   |                   |                                               |
   | progress          | Corresponds to the PARTSTAT and COMPLETED     |
   |                   | properties in iCalendar.                      |
   +-------------------+-----------------------------------------------+

             Table 3: Translation between JSTask and iCalendar

6.3.  JSGroup

   A JSGroup converts to a iCalendar VCALENDAR containing VEVENT or
   VTODO components.








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   +----------+--------------------------------------------------------+
   | Property | iCalendar counterpart                                  |
   +----------+--------------------------------------------------------+
   | entries  | The VEVENT and VTODO components within a top-level     |
   |          | VCALENDAR component.                                   |
   |          |                                                        |
   | source   | Corresponds to the SOURCE property in iCalendar.       |
   +----------+--------------------------------------------------------+

            Table 4: Translation between JSGroup and iCalendar

6.4.  Common properties

   +---------------------+---------------------------------------------+
   | Property            | iCalendar counterpart                       |
   +---------------------+---------------------------------------------+
   | alerts              | An *Alert* corresponds to the VALARM        |
   |                     | component in iCalendar, where the *action*  |
   |                     | is determined by the iCalendar ACTION       |
   |                     | property value (e.g., a "DISPLAY" property  |
   |                     | indicates that the JSCalendar Alert action  |
   |                     | is a *DisplayAction* and similarly an       |
   |                     | iCalendar "EMAIL" value for *EmailAction*   |
   |                     | action).  The *relativeTo* and *offset*     |
   |                     | properties corresponds to the iCalendar     |
   |                     | TRIGGER property.  *NON-STANDARD*: The      |
   |                     | iCalendar properties for JSCalendar Alert   |
   |                     | actions are non-standard, see               |
   |                     | [draft-daboo-valarm-extensions].            |
   |                     |                                             |
   | categories          | Corresponds to the STRUCTURED-CATEGORY      |
   |                     | property in iCalendar, see.  *NON-          |
   |                     | STANDARD*: this property is currently non-  |
   |                     | standard, see                               |
   |                     | [draft-ietf-calext-ical-relations].         |
   |                     |                                             |
   | color               | Corresponds to the COLOR property in        |
   |                     | iCalendar, as specified in [RFC7986].       |
   |                     |                                             |
   | created             | Corresponds to the CREATED property in      |
   |                     | iCalendar.                                  |
   |                     |                                             |
   | description         | Corresponds to the DESCRIPTION property in  |
   |                     | iCalendar.                                  |
   |                     |                                             |
   | htmlDescription     | There is no direct equivalent in iCalendar. |
   |                     | If the *description* is empty,              |
   |                     | implementations SHOUD store a plain text    |



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   |                     | version of *htmlDescription* in iCalendar   |
   |                     | DESCRIPTION.                                |
   |                     |                                             |
   | freeBusyStatus      | Corresponds to the TRANSP property in       |
   |                     | iCalendar.                                  |
   |                     |                                             |
   | keywords            | Corresponds to the CATEGORIES property in   |
   |                     | iCalendar, as specified in [RFC7986].       |
   |                     |                                             |
   | links               | Corresponds to the ATTACH ([RFC5545]) and   |
   |                     | IMAGE iCalendar properties ([RFC7986]).     |
   |                     |                                             |
   | locale              | Corresponds to the LANGUAGE parameter in    |
   |                     | iCalendar, which is added to individual     |
   |                     | properties.  When converting from           |
   |                     | iCalendar, one language must be picked as   |
   |                     | the main locale for the object, and all     |
   |                     | properties in other languages moved to the  |
   |                     | localizations JSEvent property.             |
   |                     |                                             |
   | localizations       | Corresponds to the LANGUAGE parameter in    |
   |                     | iCalendar, which is added to individual     |
   |                     | properties.  When converting from           |
   |                     | iCalendar, one language must be picked as   |
   |                     | the main locale for the object, and all     |
   |                     | properties in other languages moved to the  |
   |                     | localizations JSEvent property.             |
   |                     |                                             |
   | locations           | See Section 6.5.                            |
   |                     |                                             |
   | method              | Corresponds to the METHOD property in       |
   |                     | iCalendar.                                  |
   |                     |                                             |
   | participants        | See Section 6.5.                            |
   |                     |                                             |
   | priority            | Corresponds to the PRIORITY property in     |
   |                     | iCalendar.                                  |
   |                     |                                             |
   | privacy             | Corresponds to the CLASS property in        |
   |                     | iCalendar.                                  |
   |                     |                                             |
   | prodId              | Corresponds to the PRODID property in       |
   |                     | iCalendar.                                  |
   |                     |                                             |
   | recurrenceOverrides | Corresponds to the RDATE and EXDATE         |
   |                     | properties in iCalendar, plus VEVENT (for   |
   |                     | JSEvent) or VTODO (for JSTask) instances    |
   |                     | with a recurrence-id.                       |



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   |                     |                                             |
   | recurrenceRule      | Corresponds to the RRULE property in        |
   |                     | iCalendar. See the property definition at   |
   |                     | section Section 4.3.1 how to map a RRULE    |
   |                     | value.                                      |
   |                     |                                             |
   | relatedTo           | Corresponds to the RELATED-TO property in   |
   |                     | iCalendar.                                  |
   |                     |                                             |
   | replyTo             | A *replyTo* property of type "imip"         |
   |                     | corresponds to the email address of the     |
   |                     | ORGANIZER property in iCalendar. There is   |
   |                     | no iCalendar representation for the "web"   |
   |                     | type.                                       |
   |                     |                                             |
   | sequence            | Corresponds to the SEQUENCE property in     |
   |                     | iCalendar.                                  |
   |                     |                                             |
   | status              | Corresponds to the STATUS property in       |
   |                     | iCalendar (converted to lower-case).        |
   |                     |                                             |
   | title               | Corresponds to the SUMMARY property in      |
   |                     | iCalendar.                                  |
   |                     |                                             |
   | uid                 | Corresponds to the UID property in          |
   |                     | iCalendar.                                  |
   |                     |                                             |
   | updated             | Corresponds to the DTSTAMP and LAST-        |
   |                     | MODIFIED properties in iCalendar. (These    |
   |                     | are only different in the iTIP case, and    |
   |                     | the difference is not actually useful.)     |
   +---------------------+---------------------------------------------+

           Table 5: Translation between JSCalendar and iCalendar

6.5.  Locations and participants

   Both JSCalendar participants and locations have counterparts in
   iCalendar but provide richer representation.

   The following table outlines translation of JSCalendar participants.
   Where iCalendar has distinct properties for ORGANIZER and ATTENDEE,
   these are merged in JSCalendar into the Participant object type.








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   +------------------+------------------------------------------------+
   | Property         | iCalendar counterpart                          |
   +------------------+------------------------------------------------+
   | name             | the CN parameter                               |
   |                  |                                                |
   | kind             | the CUTYPE parameter                           |
   |                  |                                                |
   | rsvpResponse     | the PARTSTAT parameter                         |
   |                  |                                                |
   | role             | the ORGANIZER and ATTENDEE properties. Owners  |
   |                  | map to the iCalendar ORGANIZER property, where |
   |                  | mapping multiple owners to iCalendar is        |
   |                  | implementation-specific but MUST be consistent |
   |                  | across mappings of the same object.            |
   |                  |                                                |
   | participation    | the ROLE parameter                             |
   |                  |                                                |
   | locationId       | the JSCalendar identifier of a mapped          |
   |                  | CONFERENCE property that has the MODERATOR     |
   |                  | feature defined in its FEATURE parameter       |
   |                  | values. If multiple such CONFERENCE properties |
   |                  | are defined in iCalendar, then the one with    |
   |                  | the most interactive features is chosen (VIDEO |
   |                  | over AUDIO over CHAT over anything else).      |
   |                  |                                                |
   | rsvpWanted       | the RSVP parameter                             |
   |                  |                                                |
   | delegatedTo      | the DELEGATED-TO parameter                     |
   |                  |                                                |
   | delegatedFrom    | the DELEGATED-FROM parameter                   |
   |                  |                                                |
   | memberOf         | the MEMBER parameter                           |
   |                  |                                                |
   | scheduleSequence | the SEQUENCE property of the participant's     |
   |                  | latest iMIP message                            |
   |                  |                                                |
   | scheduleUpdated  | the DTSTAMP property of the participant's      |
   |                  | latest iMIP message                            |
   +------------------+------------------------------------------------+

   Table 6: Translation of Participant between JSCalendar and iCalendar

   For JSCalendar locations, the iCalendar counterparts are the
   [RFC5545] LOCATION and the extended iCalendar [RFC7986] CONFERENCE
   properties.

   An iCalendar LOCATION property becomes a JSCalendar Location with
   just a description property.  CONFERENCE property values in iCalendar



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   map to locations with *rel* type "virtual".  The location *feature*
   property value corresponds to the extended iCalendar FEATURE property
   parameter values defined in [RFC7986].  Both iCalendar PHONE and
   AUDIO features map to the "audio" feature and the FEED parameter
   value is omitted.  See the mapping for *locationId* in Table 6 on how
   to map CONFERENCE properties that contain the MODERATOR feature.

6.6.  Unknown properties

   Both JSCalendar and iCalendar calendar objects may contain properties
   that are not expressible in the other format.  This specification
   does not mandate how to preserve these properties.  Instead, it
   leaves negotiation on how to treat unknown properties to client and
   server implementations and their protocol used to exchange calendar
   objects.

   Two notable options to represent and preserve arbitrary iCalendar
   object properties in JSCalendar are:

   o  *JCal*: Define iCalendar properties in JCal format ([RFC7265]) in
      a vendor-specific property of the JCalendar object.  The JCal-
      formatted value may either only contain iCalendar properties that
      were not mapped to JSCalendar properties, or contain the complete
      iCalendar object representation.

   o  *Alternate link*: Define an alternate link (Section 4.2.5) value
      pointing to the iCalendar representation of the JSCalendar object.
      E.g. the alternative representation of a VEVENT would be
      represented as a link with rel "alternate" and type "text/
      calendar;component=VEVENT".

7.  JSCalendar object examples

   The following examples illustrate several aspects of the JSCalendar
   data model and format.  The examples may omit mandatory or additional
   properties, which is indicated by a placeholder property with key
   "...".  While most of the examples use calendar event objects, they
   are also illustrative for tasks.

7.1.  Simple event

   This example illustrates a simple one-time event.  It specifies a
   one-time event that begins on January 15, 2018 at 1pm New York local
   time and ends after 1 hour.







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   {
     "@type": "jsevent",
     "uid": "2a358cee-6489-4f14-a57f-c104db4dc2f1",
     "updated": "2018-01-15T18:00:00Z",
     "title": "Some event",
     "start": "2018-01-15T13:00:00",
     "timeZone": "America/New_York",
     "duration": "PT1H"
   }

7.2.  Simple task

   This example illustrates a simple task for a plain to-do item.

   {
     "@type": "jstask",
     "uid": "2a358cee-6489-4f14-a57f-c104db4dc2f2",
     "updated": "2018-01-15T18:00:00Z",
     "title": "Do something"
   }

7.3.  Simple group

   This example illustrates a simple calendar object group that contains
   an event and a task.


























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   {
     "@type": "jsgroup",
     "uid": "2a358cee-6489-4f14-a57f-c104db4dc343",
     "updated": "2018-01-15T18:00:00Z",
     "name": "A simple group",
     "entries": [
       {
         "@type": "jsevent",
         "uid": "2a358cee-6489-4f14-a57f-c104db4dc2f1",
         "updated": "2018-01-15T18:00:00Z",
         "title": "Some event",
         "start": "2018-01-15T13:00:00",
         "timeZone": "America/New_York",
         "duration": "PT1H"
       },
       {
         "@type": "jstask",
         "uid": "2a358cee-6489-4f14-a57f-c104db4dc2f2",
         "updated": "2018-01-15T18:00:00Z",
         "title": "Do something"
       }
     ]
   }

7.4.  All-day event

   This example illustrates an event for an international holiday.  It
   specifies an all-day event on April 1 that occurs every year since
   the year 1900.

   {
     "...": "",
     "title": "April Fool's Day",
     "isAllDay": true,
     "start": "1900-04-01T00:00:00",
     "duration": "P1D",
     "recurrenceRule": {
       "frequency": "yearly"
     }
   }

7.5.  Task with a due date

   This example illustrates a task with a due date.  It is a reminder to
   buy groceries before 6pm Vienna local time on January 19, 2018.  The
   calendar user expects to need 1 hour for shopping.





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   {
     "...": "",
     "title": "Buy groceries",
     "due": "2018-01-19T18:00:00",
     "timeZone": "Europe/Vienna",
     "estimatedDuration": "PT1H"
   }

7.6.  Event with end time-zone

   This example illustrates the use of end time-zones by use of an
   international flight.  The flight starts on April 1, 2018 at 9am in
   Berlin local time.  The duration of the flight is scheduled at 10
   hours 30 minutes.  The time at the flights destination is in the same
   time-zone as Tokyo.  Calendar clients could use the end time-zone to
   display the arrival time in Tokyo local time and highlight the time-
   zone difference of the flight.

   {
     "...": "",
     "title": "Flight XY51 from FRA to NRT",
     "start": "2018-04-01T09:00:00",
     "timeZone": "Europe/Berlin",
     "duration": "PT10H30M",
     "locations": {
       "2a358cee-6489-4f14-a57f-c104db4dc2f1": {
         "rel": "end",
         "timeZone": "Asia/Tokyo"
       }
     }
   }

7.7.  Floating-time event (with recurrence)

   This example illustrates the use of floating-time.  Since January 1,
   2018, a calendar user blocks 30 minutes every day to practice Yoga at
   7am local time, in whatever time-zone the user is located on that
   date.

   {
     "...": "",
     "title": "Yoga",
     "start": "2018-01-01T07:00:00",
     "duration": "PT30M",
     "recurrenceRule": {
       "frequency": "daily"
     }
   }



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7.8.  Event with multiple locations and localization

   This example illustrates an event that happens at both a physical and
   a virtual location.  Fans can see a live convert on premises or
   online.  The event title and descriptions are localized.  (Note: the
   localization of the event description contains an UTF-8 encoded
   German Umlaut.  This character may have been replaced with ASCII
   characters in the plain-text rendering of this RFC document)

   {
     "...": "",
     "title": "Live from Music Bowl: The Band",
     "description": "Go see the biggest music event ever!",
     "locale": "en",
     "start": "2018-07-04T17:00:00",
     "timeZone": "America/New_York",
     "duration": "PT3H",
     "locations": {
       "9366e041-bb4c-4aa4-b249-b4657cab925c": {
         "name": "The Music Bowl",
         "description": "Music Bowl, Central Park, New York",
         "coordinates": "geo:40.7829,73.9654"
       },
       "6f3696c6-1e07-47d0-9ce1-f50014b0041a": {
         "name": "Free live Stream from Music Bowl",
         "rel": "virtual",
         "features": [
           "video",
           "audio",
           "chat"
         ],
         "uri": "https://stream.example.com/the_band_2018"
       }
     },
     "localizations": {
       "de": {
         "title": "Live von der Music Bowl: The Band!",
         "description": "Schau dir das groesste Musikereignis an!",
         "locations/6f3696c6-1e07-47d0-9ce1-f50014b0041a/name":
                                "Gratis Live-Stream aus der Music Bowl"
       }
     }
   }








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7.9.  Recurring event with overrides

   This example illustrates the use of recurrence overrides.  A math
   course at a University is held for the first time on January 8, 2018
   at 9am London time and occurs every week until June 25, 2018.  Each
   lecture lasts for one hour and 30 minutes and is located at the
   Mathematics department.  This event has exceptional occurrences: at
   the last occurrence of the course is an exam, which lasts for 2 hours
   and starts at 10am.  Also, the location of the exam differs from the
   usual location.  On April 2, May 7 and May 28 no course is held.

   {
     "...": "",
     "title": "Calculus I",
     "start": "2018-01-08T09:00:00",
     "timeZone": "Europe/London",
     "duration": "PT1H30M",
     "locations": {
       "2a358cee-6489-4f14-a57f-c104db4dc2f1": {
         "title": "Math lab room 1",
         "description": "Math Lab I, Department of Mathematics"
       }
     },
     "recurrenceRule": {
       "frequency": "weekly",
       "until": "2018-06-25T09:00:00"
     },
     "recurrenceOverrides": {
       "2018-04-02T09:00:00": null,
       "2018-05-07T09:00:00": null,
       "2018-05-28T09:00:00": null,
       "2018-06-25T09:00:00": {
         "title": "Calculus I Exam",
         "start": "2018-06-25T10:00:00",
         "duration": "PT2H",
         "locations": {
           "2a358cee-6489-4f14-a57f-c104db4dc2f1": {
             "title": "Big Auditorium",
             "description": "Big Auditorium, Other Road"
           }
         }
       }
     }
   }







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7.10.  Recurring event with participants

   This example illustrates scheduled events.  A team meeting occurs
   every week since January 8, 2018 at 9am Johannesburg time.  The event
   owner also chairs the event.  Participants meet in a virtual meeting
   room.  An attendee has accepted the invitation, but on March 8, 2018
   he is unavailable and declined participation for this occurrence.

   {
     "...": "",
     "title": "FooBar team meeting",
     "start": "2018-01-08T09:00:00",
     "timeZone": "Africa/Johannesburg",
     "duration": "PT1H",
     "locations": {
       "2a358cee-6489-4f14-a57f-c104db4dc2f1": {
         "title": "ChatMe meeting room",
         "rel": "virtual",
         "features": [
           "audio",
           "chat",
           "video"
         ],
         "uri": "https://chatme.example.com?id=1234567"
       }
     },
     "recurrenceRule": {
       "frequency": "weekly"
     },
     "replyTo": {
       "imip": "zoe@foobar.example.com"
     },
     "participants": {
       "tom@foobar.example.com": {
         "name": "Tom Tool",
         "email": "tom@foobar.example.com",
         "rsvpResponse": "accepted",
         "roles": [
           "attendee"
         ]
       },
       "zoe@foobar.example.com": {
         "name": "Zoe Zelda",
         "email": "zoe@foobar.example.com",
         "rsvpResponse": "accepted",
         "roles": [
           "owner",
           "chair"



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         ]
       },
       "...": ""
     },
     "recurrenceOverrides": {
       "2018-03-08T09:00:00": {
         "participants/tom@foobar.example.com/rsvpResponse": "declined"
       }
     }
   }

8.  Security Considerations

   The use of JSON as a format does have its own inherent security risks
   as discussed in Section 12 of [RFC8259].  Even though JSON is
   considered a safe subset of JavaScript, it should be kept in mind
   that a flaw in the parser processing JSON could still impose a
   threat, which doesn't arise with conventional iCalendar data.

   With this in mind, a parser for JSON data aware of the security
   implications should be used for the format described in this
   document.  For example, the use of JavaScript's "eval()" function is
   considered an unacceptable security risk, as described in Section 12
   of[RFC8259].  A native parser with full awareness of the JSON format
   should be preferred.

9.  IANA Considerations

   This document amends the "application/calendar" MIME media type
   defined in [RFC7265].

   New optional parameter: "type" with value being one of "jsevent",
   "jstask", "jsgroup".  The parameter MUST NOT occur more than once.

10.  Acknowledgments

   The authors would like to thank the members of CalConnect for their
   valuable contributions.  This specification originated from the work
   of the API technical committee of CalConnect, the Calendaring and
   Scheduling Consortium.

11.  References

11.1.  Normative References







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

   [RFC2183]  Troost, R., Dorner, S., and K. Moore, Ed., "Communicating
              Presentation Information in Internet Messages: The
              Content-Disposition Header Field", RFC 2183,
              DOI 10.17487/RFC2183, August 1997,
              <https://www.rfc-editor.org/info/rfc2183>.

   [RFC2392]  Levinson, E., "Content-ID and Message-ID Uniform Resource
              Locators", RFC 2392, DOI 10.17487/RFC2392, August 1998,
              <https://www.rfc-editor.org/info/rfc2392>.

   [RFC3339]  Klyne, G. and C. Newman, "Date and Time on the Internet:
              Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,
              <https://www.rfc-editor.org/info/rfc3339>.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, DOI 10.17487/RFC3986, January 2005,
              <https://www.rfc-editor.org/info/rfc3986>.

   [RFC4122]  Leach, P., Mealling, M., and R. Salz, "A Universally
              Unique IDentifier (UUID) URN Namespace", RFC 4122,
              DOI 10.17487/RFC4122, July 2005,
              <https://www.rfc-editor.org/info/rfc4122>.

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

   [RFC5545]  Desruisseaux, B., Ed., "Internet Calendaring and
              Scheduling Core Object Specification (iCalendar)",
              RFC 5545, DOI 10.17487/RFC5545, September 2009,
              <https://www.rfc-editor.org/info/rfc5545>.

   [RFC5546]  Daboo, C., Ed., "iCalendar Transport-Independent
              Interoperability Protocol (iTIP)", RFC 5546,
              DOI 10.17487/RFC5546, December 2009,
              <https://www.rfc-editor.org/info/rfc5546>.

   [RFC5646]  Phillips, A., Ed. and M. Davis, Ed., "Tags for Identifying
              Languages", BCP 47, RFC 5646, DOI 10.17487/RFC5646,
              September 2009, <https://www.rfc-editor.org/info/rfc5646>.




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   [RFC5870]  Mayrhofer, A. and C. Spanring, "A Uniform Resource
              Identifier for Geographic Locations ('geo' URI)",
              RFC 5870, DOI 10.17487/RFC5870, June 2010,
              <https://www.rfc-editor.org/info/rfc5870>.

   [RFC6047]  Melnikov, A., Ed., "iCalendar Message-Based
              Interoperability Protocol (iMIP)", RFC 6047,
              DOI 10.17487/RFC6047, December 2010,
              <https://www.rfc-editor.org/info/rfc6047>.

   [RFC6570]  Gregorio, J., Fielding, R., Hadley, M., Nottingham, M.,
              and D. Orchard, "URI Template", RFC 6570,
              DOI 10.17487/RFC6570, March 2012,
              <https://www.rfc-editor.org/info/rfc6570>.

   [RFC6838]  Freed, N., Klensin, J., and T. Hansen, "Media Type
              Specifications and Registration Procedures", BCP 13,
              RFC 6838, DOI 10.17487/RFC6838, January 2013,
              <https://www.rfc-editor.org/info/rfc6838>.

   [RFC6901]  Bryan, P., Ed., Zyp, K., and M. Nottingham, Ed.,
              "JavaScript Object Notation (JSON) Pointer", RFC 6901,
              DOI 10.17487/RFC6901, April 2013,
              <https://www.rfc-editor.org/info/rfc6901>.

   [RFC7265]  Kewisch, P., Daboo, C., and M. Douglass, "jCal: The JSON
              Format for iCalendar", RFC 7265, DOI 10.17487/RFC7265, May
              2014, <https://www.rfc-editor.org/info/rfc7265>.

   [RFC7493]  Bray, T., Ed., "The I-JSON Message Format", RFC 7493,
              DOI 10.17487/RFC7493, March 2015,
              <https://www.rfc-editor.org/info/rfc7493>.

   [RFC7529]  Daboo, C. and G. Yakushev, "Non-Gregorian Recurrence Rules
              in the Internet Calendaring and Scheduling Core Object
              Specification (iCalendar)", RFC 7529,
              DOI 10.17487/RFC7529, May 2015,
              <https://www.rfc-editor.org/info/rfc7529>.

   [RFC7986]  Daboo, C., "New Properties for iCalendar", RFC 7986,
              DOI 10.17487/RFC7986, October 2016,
              <https://www.rfc-editor.org/info/rfc7986>.

   [RFC8259]  Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
              Interchange Format", STD 90, RFC 8259,
              DOI 10.17487/RFC8259, December 2017,
              <https://www.rfc-editor.org/info/rfc8259>.




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   [RFC8288]  Nottingham, M., "Web Linking", RFC 8288,
              DOI 10.17487/RFC8288, October 2017,
              <https://www.rfc-editor.org/info/rfc8288>.

11.2.  Informative References

   [draft-apthorp-ical-tasks]
              "Task Extensions to iCalendar",
              <https://tools.ietf.org/html/draft-apthorp-ical-tasks>.

   [draft-daboo-valarm-extensions]
              "VALARM Extensions for iCalendar",
              <https://tools.ietf.org/html/
              draft-daboo-valarm-extensions>.

   [draft-ietf-calext-ical-relations]
              "Support for iCalendar Relationships",
              <https://tools.ietf.org/html/
              draft-ietf-calext-ical-relations>.

11.3.  URIs

   [1] https://www.w3.org/TR/html/

   [2] https://www.iana.org/assignments/link-relations/link-
       relations.xhtml

   [3] https://www.w3.org/TR/2011/REC-css3-color-20110607/#svg-color

   [4] http://www.iana.org/time-zones

Authors' Addresses

   Neil Jenkins
   FastMail
   PO Box 234
   Collins St West
   Melbourne  VIC 8007
   Australia

   Email: neilj@fastmailteam.com
   URI:   https://www.fastmail.com









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   Robert Stepanek
   FastMail
   PO Box 234
   Collins St West
   Melbourne  VIC 8007
   Australia

   Email: rsto@fastmailteam.com
   URI:   https://www.fastmail.com










































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