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<rfc category="std"
updates='5545'
docName="draft-ietf-calext-ical-relations-11" ipr="trust200902">
<?rfc strict="yes" ?>
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<?rfc tocdepth="5"?>
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<front> <front>
<title abbrev="iCalendar Relationships">Support for iCalendar Relationships< /title> <title abbrev="iCalendar Relationships">Support for iCalendar Relationships< /title>
<seriesInfo name="RFC" value="9253" stream="IETF"/>
<!-- add 'role="editor"' below for the editors if appropriate -->
<author initials="M." surname="Douglass" fullname="Michael Douglass"> <author initials="M." surname="Douglass" fullname="Michael Douglass">
<organization abbrev="Bedework">Bedework</organization> <organization abbrev="Bedework" showOnFrontPage="true">Bedework</organizat ion>
<address> <address>
<postal> <postal>
<street>226 3rd Street</street> <street>226 3rd Street</street>
<city>Troy</city> <city>Troy</city>
<region>NY</region> <region>NY</region>
<code>12180</code> <code>12180</code>
<country>USA</country> <country>United States of America</country>
</postal> </postal>
<email>mdouglass@bedework.com</email> <email>mdouglass@bedework.com</email>
<uri>https://bedework.com</uri> <uri>https://bedework.com</uri>
</address> </address>
</author> </author>
<date month="08" year="2022"/>
<date day='22' month='March' year='2022' /> <area>art</area>
<workgroup>calext</workgroup>
<area>Applications</area>
<keyword>iCalendar</keyword> <keyword>iCalendar</keyword>
<keyword>link</keyword> <keyword>link</keyword>
<keyword>related-to</keyword> <keyword>related-to</keyword>
<keyword>relationships</keyword> <keyword>relationships</keyword>
<abstract pn="section-abstract">
<abstract> <t indent="0" pn="section-abstract-1">
<t>
This specification updates the iCalendar RELATED-TO property This specification updates the iCalendar RELATED-TO property
defined in RFC5545 defined in RFC 5545
by adding new relation types and introduces new iCalendar by adding new relation types and introduces new iCalendar
properties LINK, CONCEPT and REFID to allow better properties (LINK, CONCEPT, and REFID) to allow better
linking and grouping of iCalendar components and related data. linking and grouping of iCalendar components and related data.
</t> </t>
</abstract> </abstract>
<boilerplate>
<section anchor="status-of-memo" numbered="false" removeInRFC="false" toc=
"exclude" pn="section-boilerplate.1">
<name slugifiedName="name-status-of-this-memo">Status of This Memo</name
>
<t indent="0" pn="section-boilerplate.1-1">
This is an Internet Standards Track document.
</t>
<t indent="0" pn="section-boilerplate.1-2">
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by
the Internet Engineering Steering Group (IESG). Further
information on Internet Standards is available in Section 2 of
RFC 7841.
</t>
<t indent="0" pn="section-boilerplate.1-3">
Information about the current status of this document, any
errata, and how to provide feedback on it may be obtained at
<eref target="https://www.rfc-editor.org/info/rfc9253" brackets="non
e"/>.
</t>
</section>
<section anchor="copyright" numbered="false" removeInRFC="false" toc="excl
ude" pn="section-boilerplate.2">
<name slugifiedName="name-copyright-notice">Copyright Notice</name>
<t indent="0" pn="section-boilerplate.2-1">
Copyright (c) 2022 IETF Trust and the persons identified as the
document authors. All rights reserved.
</t>
<t indent="0" pn="section-boilerplate.2-2">
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(<eref target="https://trustee.ietf.org/license-info" brackets="none
"/>) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with
respect to this document. Code Components extracted from this
document must include Revised BSD License text as described in
Section 4.e of the Trust Legal Provisions and are provided without
warranty as described in the Revised BSD License.
</t>
</section>
</boilerplate>
<toc>
<section anchor="toc" numbered="false" removeInRFC="false" toc="exclude" p
n="section-toc.1">
<name slugifiedName="name-table-of-contents">Table of Contents</name>
<ul bare="true" empty="true" indent="2" spacing="compact" pn="section-to
c.1-1">
<li pn="section-toc.1-1.1">
<t indent="0" pn="section-toc.1-1.1.1"><xref derivedContent="1" form
at="counter" sectionFormat="of" target="section-1"/>.  <xref derivedContent="" f
ormat="title" sectionFormat="of" target="name-introduction">Introduction</xref><
/t>
<ul bare="true" empty="true" indent="2" spacing="compact" pn="sectio
n-toc.1-1.1.2">
<li pn="section-toc.1-1.1.2.1">
<t indent="0" keepWithNext="true" pn="section-toc.1-1.1.2.1.1"><
xref derivedContent="1.1" format="counter" sectionFormat="of" target="section-1.
1"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-st
ructured-icalendar-relati">Structured iCalendar Relationships</xref></t>
</li>
<li pn="section-toc.1-1.1.2.2">
<t indent="0" keepWithNext="true" pn="section-toc.1-1.1.2.2.1"><
xref derivedContent="1.2" format="counter" sectionFormat="of" target="section-1.
2"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-gr
ouped-icalendar-relations">Grouped iCalendar Relationships</xref></t>
</li>
<li pn="section-toc.1-1.1.2.3">
<t indent="0" keepWithNext="true" pn="section-toc.1-1.1.2.3.1"><
xref derivedContent="1.3" format="counter" sectionFormat="of" target="section-1.
3"/>.  <xref derivedContent="" format="title" sectionFormat="of" target="name-co
ncept-relationships">Concept Relationships</xref></t>
</li>
<li pn="section-toc.1-1.1.2.4">
<t indent="0" pn="section-toc.1-1.1.2.4.1"><xref derivedContent=
"1.4" format="counter" sectionFormat="of" target="section-1.4"/>.  <xref derived
Content="" format="title" sectionFormat="of" target="name-linked-relationships">
Linked Relationships</xref></t>
</li>
<li pn="section-toc.1-1.1.2.5">
<t indent="0" pn="section-toc.1-1.1.2.5.1"><xref derivedContent=
"1.5" format="counter" sectionFormat="of" target="section-1.5"/>.  <xref derived
Content="" format="title" sectionFormat="of" target="name-caching-and-offline-us
e">Caching and Offline Use</xref></t>
</li>
<li pn="section-toc.1-1.1.2.6">
<t indent="0" pn="section-toc.1-1.1.2.6.1"><xref derivedContent=
"1.6" format="counter" sectionFormat="of" target="section-1.6"/>.  <xref derived
Content="" format="title" sectionFormat="of" target="name-conventions-used-in-th
is-do">Conventions Used in This Document</xref></t>
</li>
</ul>
</li>
<li pn="section-toc.1-1.2">
<t indent="0" pn="section-toc.1-1.2.1"><xref derivedContent="2" form
at="counter" sectionFormat="of" target="section-2"/>.  <xref derivedContent="" f
ormat="title" sectionFormat="of" target="name-link-property-reference-typ">LINK
Property Reference Types</xref></t>
</li>
<li pn="section-toc.1-1.3">
<t indent="0" pn="section-toc.1-1.3.1"><xref derivedContent="3" form
at="counter" sectionFormat="of" target="section-3"/>.  <xref derivedContent="" f
ormat="title" sectionFormat="of" target="name-link-relation-types">Link Relation
Types</xref></t>
</li>
<li pn="section-toc.1-1.4">
<t indent="0" pn="section-toc.1-1.4.1"><xref derivedContent="4" form
at="counter" sectionFormat="of" target="section-4"/>.  <xref derivedContent="" f
ormat="title" sectionFormat="of" target="name-new-temporal-reltype-parame">New T
emporal RELTYPE Parameter Values</xref></t>
</li>
<li pn="section-toc.1-1.5">
<t indent="0" pn="section-toc.1-1.5.1"><xref derivedContent="5" form
at="counter" sectionFormat="of" target="section-5"/>.  <xref derivedContent="" f
ormat="title" sectionFormat="of" target="name-additional-new-reltype-para">Addit
ional New RELTYPE Parameter Values</xref></t>
</li>
<li pn="section-toc.1-1.6">
<t indent="0" pn="section-toc.1-1.6.1"><xref derivedContent="6" form
at="counter" sectionFormat="of" target="section-6"/>.  <xref derivedContent="" f
ormat="title" sectionFormat="of" target="name-new-property-parameters">New Prope
rty Parameters</xref></t>
<ul bare="true" empty="true" indent="2" spacing="compact" pn="sectio
n-toc.1-1.6.2">
<li pn="section-toc.1-1.6.2.1">
<t indent="0" pn="section-toc.1-1.6.2.1.1"><xref derivedContent=
"6.1" format="counter" sectionFormat="of" target="section-6.1"/>.  <xref derived
Content="" format="title" sectionFormat="of" target="name-link-relation">Link Re
lation</xref></t>
</li>
<li pn="section-toc.1-1.6.2.2">
<t indent="0" pn="section-toc.1-1.6.2.2.1"><xref derivedContent=
"6.2" format="counter" sectionFormat="of" target="section-6.2"/>.  <xref derived
Content="" format="title" sectionFormat="of" target="name-gap">Gap</xref></t>
</li>
</ul>
</li>
<li pn="section-toc.1-1.7">
<t indent="0" pn="section-toc.1-1.7.1"><xref derivedContent="7" form
at="counter" sectionFormat="of" target="section-7"/>.  <xref derivedContent="" f
ormat="title" sectionFormat="of" target="name-new-value-data-types">New Value Da
ta Types</xref></t>
</li>
<li pn="section-toc.1-1.8">
<t indent="0" pn="section-toc.1-1.8.1"><xref derivedContent="8" form
at="counter" sectionFormat="of" target="section-8"/>.  <xref derivedContent="" f
ormat="title" sectionFormat="of" target="name-new-properties">New Properties</xr
ef></t>
<ul bare="true" empty="true" indent="2" spacing="compact" pn="sectio
n-toc.1-1.8.2">
<li pn="section-toc.1-1.8.2.1">
<t indent="0" pn="section-toc.1-1.8.2.1.1"><xref derivedContent=
"8.1" format="counter" sectionFormat="of" target="section-8.1"/>.  <xref derived
Content="" format="title" sectionFormat="of" target="name-concept">Concept</xref
></t>
</li>
<li pn="section-toc.1-1.8.2.2">
<t indent="0" pn="section-toc.1-1.8.2.2.1"><xref derivedContent=
"8.2" format="counter" sectionFormat="of" target="section-8.2"/>.  <xref derived
Content="" format="title" sectionFormat="of" target="name-link">Link</xref></t>
</li>
<li pn="section-toc.1-1.8.2.3">
<t indent="0" pn="section-toc.1-1.8.2.3.1"><xref derivedContent=
"8.3" format="counter" sectionFormat="of" target="section-8.3"/>.  <xref derived
Content="" format="title" sectionFormat="of" target="name-refid">Refid</xref></t
>
</li>
</ul>
</li>
<li pn="section-toc.1-1.9">
<t indent="0" pn="section-toc.1-1.9.1"><xref derivedContent="9" form
at="counter" sectionFormat="of" target="section-9"/>.  <xref derivedContent="" f
ormat="title" sectionFormat="of" target="name-updates-to-rfc-5545">Updates to RF
C 5545</xref></t>
<ul bare="true" empty="true" indent="2" spacing="compact" pn="sectio
n-toc.1-1.9.2">
<li pn="section-toc.1-1.9.2.1">
<t indent="0" pn="section-toc.1-1.9.2.1.1"><xref derivedContent=
"9.1" format="counter" sectionFormat="of" target="section-9.1"/>.  <xref derived
Content="" format="title" sectionFormat="of" target="name-related-to">RELATED-TO
</xref></t>
</li>
</ul>
</li>
<li pn="section-toc.1-1.10">
<t indent="0" pn="section-toc.1-1.10.1"><xref derivedContent="10" fo
rmat="counter" sectionFormat="of" target="section-10"/>. <xref derivedContent=""
format="title" sectionFormat="of" target="name-security-considerations">Securit
y Considerations</xref></t>
</li>
<li pn="section-toc.1-1.11">
<t indent="0" pn="section-toc.1-1.11.1"><xref derivedContent="11" fo
rmat="counter" sectionFormat="of" target="section-11"/>. <xref derivedContent=""
format="title" sectionFormat="of" target="name-iana-considerations">IANA Consid
erations</xref></t>
<ul bare="true" empty="true" indent="2" spacing="compact" pn="sectio
n-toc.1-1.11.2">
<li pn="section-toc.1-1.11.2.1">
<t indent="0" pn="section-toc.1-1.11.2.1.1"><xref derivedContent
="11.1" format="counter" sectionFormat="of" target="section-11.1"/>.  <xref deri
vedContent="" format="title" sectionFormat="of" target="name-icalendar-property-
registra">iCalendar Property Registrations</xref></t>
</li>
<li pn="section-toc.1-1.11.2.2">
<t indent="0" pn="section-toc.1-1.11.2.2.1"><xref derivedContent
="11.2" format="counter" sectionFormat="of" target="section-11.2"/>.  <xref deri
vedContent="" format="title" sectionFormat="of" target="name-icalendar-property-
paramete">iCalendar Property Parameter Registrations</xref></t>
</li>
<li pn="section-toc.1-1.11.2.3">
<t indent="0" pn="section-toc.1-1.11.2.3.1"><xref derivedContent
="11.3" format="counter" sectionFormat="of" target="section-11.3"/>.  <xref deri
vedContent="" format="title" sectionFormat="of" target="name-icalendar-value-dat
a-type-r">iCalendar Value Data Type Registrations</xref></t>
</li>
<li pn="section-toc.1-1.11.2.4">
<t indent="0" pn="section-toc.1-1.11.2.4.1"><xref derivedContent
="11.4" format="counter" sectionFormat="of" target="section-11.4"/>.  <xref deri
vedContent="" format="title" sectionFormat="of" target="name-icalendar-reltype-v
alue-reg">iCalendar RELTYPE Value Registrations</xref></t>
</li>
</ul>
</li>
<li pn="section-toc.1-1.12">
<t indent="0" pn="section-toc.1-1.12.1"><xref derivedContent="12" fo
rmat="counter" sectionFormat="of" target="section-12"/>. <xref derivedContent=""
format="title" sectionFormat="of" target="name-references">References</xref></t
>
<ul bare="true" empty="true" indent="2" spacing="compact" pn="sectio
n-toc.1-1.12.2">
<li pn="section-toc.1-1.12.2.1">
<t indent="0" pn="section-toc.1-1.12.2.1.1"><xref derivedContent
="12.1" format="counter" sectionFormat="of" target="section-12.1"/>.  <xref deri
vedContent="" format="title" sectionFormat="of" target="name-normative-reference
s">Normative References</xref></t>
</li>
<li pn="section-toc.1-1.12.2.2">
<t indent="0" pn="section-toc.1-1.12.2.2.1"><xref derivedContent
="12.2" format="counter" sectionFormat="of" target="section-12.2"/>.  <xref deri
vedContent="" format="title" sectionFormat="of" target="name-informative-referen
ces">Informative References</xref></t>
</li>
</ul>
</li>
<li pn="section-toc.1-1.13">
<t indent="0" pn="section-toc.1-1.13.1"><xref derivedContent="" form
at="none" sectionFormat="of" target="section-appendix.a"/><xref derivedContent="
" format="title" sectionFormat="of" target="name-acknowledgements">Acknowledgeme
nts</xref></t>
</li>
<li pn="section-toc.1-1.14">
<t indent="0" pn="section-toc.1-1.14.1"><xref derivedContent="" form
at="none" sectionFormat="of" target="section-appendix.b"/><xref derivedContent="
" format="title" sectionFormat="of" target="name-authors-address">Author's Addre
ss</xref></t>
</li>
</ul>
</section>
</toc>
</front> </front>
<middle> <middle>
<section title="Introduction"> <section numbered="true" removeInRFC="false" toc="include" pn="section-1">
<t> <name slugifiedName="name-introduction">Introduction</name>
iCalendar entities defined in <xref target='RFC5545'/> often <t indent="0" pn="section-1-1">
iCalendar entities defined in <xref target="RFC5545" format="default" se
ctionFormat="of" derivedContent="RFC5545"/> often
need to be related to each other or to need to be related to each other or to
associated meta-data. The specifications below support associated metadata. The specifications below support
relationships of the following forms: relationships of the following forms:
<list style='hanging'> </t>
<t hangText="Structured iCalendar:"> <dl newline="false" spacing="normal" indent="3" pn="section-1-2">
<dt pn="section-1-2.1">Structured iCalendar:</dt>
<dd pn="section-1-2.2">
iCalendar entities can be related to each other in some structured iCalendar entities can be related to each other in some structured
way, for example as parent, sibling, before, after. way, for example, as parent, sibling, before, or after.
</t> </dd>
<t hangText="Grouped iCalendar:"> <dt pn="section-1-2.3">Grouped iCalendar:</dt>
<dd pn="section-1-2.4">
iCalendar entities can be related to each other as a group. iCalendar entities can be related to each other as a group.
CATEGORIES are often used for this purpose but are problematic CATEGORIES are often used for this purpose but are problematic
for application developers due to their lack of consistency for application developers due to their lack of consistency
and use as a free-form tag. and use as a free-form tag.
</t> </dd>
<t hangText="Linked:"> <dt pn="section-1-2.5">Linked:</dt>
Entities can be linked to other entities such as vcards <dd pn="section-1-2.6">
Entities can be linked to other entities, such as vCards,
through a URI and associated REL and FMTTYPE parameters. through a URI and associated REL and FMTTYPE parameters.
</t> </dd>
</list> </dl>
</t> <section numbered="true" removeInRFC="false" toc="include" pn="section-1.1
">
<section title="Structured iCalendar relationships"> <name slugifiedName="name-structured-icalendar-relati">Structured iCalen
<t> dar Relationships</name>
The iCalendar <xref target='RFC5545'/> <t indent="0" pn="section-1.1-1">
The iCalendar <xref target="RFC5545" format="default" sectionFormat="o
f" derivedContent="RFC5545"/>
RELATED-TO property has no support for temporal relationships RELATED-TO property has no support for temporal relationships
as used by project management tools. as used by project management tools.
</t> </t>
<t indent="0" pn="section-1.1-2">
<t>
The RELTYPE parameter is extended to take new values The RELTYPE parameter is extended to take new values
defining temporal relationships, a GAP parameter is defined to provide defining temporal relationships, a GAP parameter is defined to provide
lead and lag values, and RELATED-TO is extended to allow URI values. lead and lag values, and RELATED-TO is extended to allow URI values.
These changes allow the RELATED-TO property to define a richer set of These changes allow the RELATED-TO property to define a richer set of
relationships useful for project management. relationships useful for project management.
</t> </t>
</section> </section>
<section numbered="true" removeInRFC="false" toc="include" pn="section-1.2
<section title="Grouped iCalendar relationships"> ">
<t> <name slugifiedName="name-grouped-icalendar-relations">Grouped iCalendar
This specification defines a new REFID property which Relationships</name>
<t indent="0" pn="section-1.2-1">
This specification defines a new REFID property, which
allows arbitrary groups of entities to be associated with the same allows arbitrary groups of entities to be associated with the same
key value. key value.
</t> </t>
<t indent="0" pn="section-1.2-2">
<t>
REFID is used to identify a key allowing the association of REFID is used to identify a key allowing the association of
components that are all related to the referring, aggregating components that are all related to the referring, aggregating
component and the retrieval of components based on this key. component and the retrieval of components based on this key.
For example, this may be used to identify the tasks associated For example, this may be used to identify the tasks associated
with a given project without having to communicate the task with a given project without having to communicate the task
structure of the project. A further example is the grouping structure of the project. A further example is the grouping
of all sub-tasks associated with the delivery of a specific of all sub-tasks associated with the delivery of a specific
package in a package delivery system. package in a package delivery system.
</t> </t>
<t indent="0" pn="section-1.2-3">
<t>
As such, the presence of a REFID property imparts no meaning As such, the presence of a REFID property imparts no meaning
to the component. It is merely a key to allow retrieval. This is to the component. It is merely a key to allow retrieval. This is
distinct from categorisation which, while allowing grouping distinct from categorization, which, while allowing grouping,
also adds meaning to the component to which it is attached. also adds meaning to the component to which it is attached.
</t> </t>
</section> </section>
<section numbered="true" removeInRFC="false" toc="include" pn="section-1.3
<section title="Concept relationships"> ">
<t> <name slugifiedName="name-concept-relationships">Concept Relationships</
name>
<t indent="0" pn="section-1.3-1">
The name CONCEPT is used by the Simple Knowledge Organization The name CONCEPT is used by the Simple Knowledge Organization
System defined in <xref target='W3C.REC-skos-reference-20090818'/>. System, as defined in <xref target="W3C.REC-skos-reference-20090818" f ormat="default" sectionFormat="of" derivedContent="W3C.REC-skos-reference-200908 18"/>.
The term "concept" more accurately defines what we often The term "concept" more accurately defines what we often
mean by a category. It's not the text string that is important mean by a category. It's not the text string that is important
but the meaning attached to it. For example, the term but the meaning attached to it. For example, the term
"football" can mean very different sports. "football" can mean very different sports.
</t> </t>
<t indent="0" pn="section-1.3-2">
<t>
The introduction of CONCEPT allows a more structured The introduction of CONCEPT allows a more structured
approach to categorization, with the possibility of namespaced approach to categorization, with the possibility of namespaced
and path-like values. Unlike REFID the CONCEPT property imparts some and path-like values. Unlike REFID, the CONCEPT property imparts some
meaning. It is assumed that the value of this property will meaning. It is assumed that the value of this property will
reference a well defined category. reference a well-defined category.
</t> </t>
<t indent="0" pn="section-1.3-3">
<t> The current CATEGORIES property defined in <xref target="RFC5545" form
The current <xref target='RFC5545'/> CATEGORY property is used at="default" sectionFormat="of" derivedContent="RFC5545"/> is used
as a free form 'tagging' field. These values have some meaning as a free-form 'tagging' field. These values have some meaning
to those who apply them but not necessarily to any consumer. to those who apply them but not necessarily to any consumer.
As such it is difficult to establish As such, it is difficult to establish
formal relationships between components based on their category. formal relationships between components based on their category.
</t> </t>
<t indent="0" pn="section-1.3-4">
<t> Rather than attempt to add semantics to the CATEGORIES property,
Rather than attempt to add semantics to the CATEGORY property
it seems best to continue its usage as an informal tag and it seems best to continue its usage as an informal tag and
establish a new CONCEPT property with more constraints. establish a new CONCEPT property with more constraints.
</t> </t>
</section> </section>
<section numbered="true" removeInRFC="false" toc="include" pn="section-1.4
<section title="Linked relationships"> ">
<t> <name slugifiedName="name-linked-relationships">Linked Relationships</na
The currently existing iCalendar standard <xref target='RFC5545'/> lac me>
ks <t indent="0" pn="section-1.4-1">
The currently existing iCalendar standard <xref target="RFC5545" forma
t="default" sectionFormat="of" derivedContent="RFC5545"/> lacks
a general purpose method for referencing additional, external informat ion a general purpose method for referencing additional, external informat ion
relating to calendar components. relating to calendar components.
</t> </t>
<t indent="0" pn="section-1.4-2">
<t>
This document proposes a method for referencing typed external This document proposes a method for referencing typed external
information that can provide additional information about an iCalendar information that can provide additional information about an iCalendar
component. This new LINK property is closely aligned to component. This new LINK property is closely aligned to
<xref target='RFC8288'/> which defines the generic concept <xref target="RFC8288" format="default" sectionFormat="of" derivedCont
of Web Linking as well as its expression in the HTTP LINK header ent="RFC8288"/>, which defines the generic concept
of Web Linking, as well as its expression in the HTTP LINK header
field. field.
</t> </t>
<t indent="0" pn="section-1.4-3">
<t>
The LINK property defines a typed reference or relation to external The LINK property defines a typed reference or relation to external
meta-data or related resources. By providing type and format informati on metadata or related resources. By providing type and format informatio n
as parameters, clients and servers are able to discover interesting as parameters, clients and servers are able to discover interesting
references and make use of them, perhaps for indexing or the references and make use of them, perhaps for indexing or the
presentation of interesting links for the user. presentation of interesting links for the user.
</t> </t>
<t indent="0" pn="section-1.4-4">
<t>
Calendar components are often grouped into collections to represent a Calendar components are often grouped into collections to represent a
calendar or a series of tasks, for example <xref target='RFC4791'/>' ( calendar or a series of tasks, for example, Calendaring Extensions to
CalDAV) calendar WebDAV (CalDAV) calendar collections <xref target="RFC4791" format="def
collections. ault" sectionFormat="of" derivedContent="RFC4791"/>.
</t> </t>
<t indent="0" pn="section-1.4-5">
<t>
It is also often necessary to reference calendar components It is also often necessary to reference calendar components
in other collections. For example, a VEVENT might refer to in other collections. For example, a VEVENT might refer to
a VTODO from which it was derived. The PARENT, SIBLING and CHILD a VTODO from which it was derived. The PARENT, SIBLING, and CHILD
relationships defined for the relationships defined for the
RELATED-TO property only allow for a UID which is inadequate for many RELATED-TO property only allow for a unique identifier (UID), which is inadequate for many
purposes. Allowing other value types for those relationships may help purposes. Allowing other value types for those relationships may help
but would cause but would cause
backward compatibility issues. The LINK property can link components backward-compatibility issues. The LINK property can link components
in different collections or even on different servers. in different collections or even on different servers.
</t> </t>
<t indent="0" pn="section-1.4-6">
<t> When publishing events, it is useful to be able to refer back to the
When publishing events it is useful to be able to refer back to the
source of that information. The actual event may have been consumed fr om source of that information. The actual event may have been consumed fr om
a feed or an ics file on a web site. A LINK property can provide a feed or an ics file on a website. A LINK property can provide
a reference to the originator of the event. a reference to the originator of the event.
</t> </t>
<t indent="0" pn="section-1.4-7">
<t>
Beyond the need to relate elements temporally, project Beyond the need to relate elements temporally, project
management tools often need to be able to specify the relationships management tools often need to be able to specify the relationships
between the various events and tasks which make up a project. between the various events and tasks that make up a project.
The LINK property provides such a mechanism. The LINK property provides such a mechanism.
</t> </t>
<t indent="0" pn="section-1.4-8">
<t> The LINK property <bcp14>MUST NOT</bcp14> be treated as just another
The LINK property MUST NOT be treated as just another
attachment. The ATTACH property defined in attachment. The ATTACH property defined in
<xref target='RFC5545'/> has been extended by <xref target="RFC5545" format="default" sectionFormat="of" derivedCont
<xref target='RFC8607'/> ent="RFC5545"/> has been extended by
<xref target="RFC8607" format="default" sectionFormat="of" derivedCont
ent="RFC8607"/>
to handle server-side management and stripping of inline data and to to handle server-side management and stripping of inline data and to
provide additional data about the attachment (size, filename etc). provide additional data about the attachment (size, filename, etc.).
</t> </t>
<t indent="0" pn="section-1.4-9">
<t> Additionally, clients may choose to handle attachments differently
Additionally clients may choose to handle attachments differently from the LINK property, as attachments are often an integral part
from the LINK property as attachments are often an integral part of the message, for example, the agenda.
of the message - for example, the agenda.
</t> </t>
</section> </section>
<section anchor="caching" numbered="true" removeInRFC="false" toc="include
<section anchor="caching" title='Caching and offline use'> " pn="section-1.5">
<t> <name slugifiedName="name-caching-and-offline-use">Caching and Offline U
se</name>
<t indent="0" pn="section-1.5-1">
In general, the calendar entity should be self explanatory In general, the calendar entity should be self explanatory
without the need to download referenced meta-data such as a without the need to download referenced metadata, such as a
web page. web page.
</t> </t>
<t> <t indent="0" pn="section-1.5-2">
However, to facilitate offline display the link type may identify However, to facilitate offline display, the link type may identify
important pieces of data which should be downloaded in important pieces of data that should be downloaded in
advance. advance.
</t> </t>
</section> </section>
<section anchor="conventions" numbered="true" removeInRFC="false" toc="inc
<section anchor="conventions" lude" pn="section-1.6">
title='Conventions Used in This Document'> <name slugifiedName="name-conventions-used-in-this-do">Conventions Used
<t> in This Document</name>
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL <t indent="0" pn="section-1.6-1">
NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", The key words "<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>",
"MAY" and "OPTIONAL" in this document are to be interpreted as "<bcp14>REQUIRED</bcp14>", "<bcp14>SHALL</bcp14>", "<bcp14>SHALL NOT</bcp14>
described in BCP 14 <xref target='RFC2119'/> ", "<bcp14>SHOULD</bcp14>", "<bcp14>SHOULD NOT</bcp14>",
<xref target='RFC8174'/> when, and only when, they "<bcp14>RECOMMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>",
appear in all capitals, as shown here. "<bcp14>MAY</bcp14>", and "<bcp14>OPTIONAL</bcp14>" in this document are
to be interpreted as described in BCP 14 <xref target="RFC2119" format="defa
ult" sectionFormat="of" derivedContent="RFC2119"/>
<xref target="RFC8174" format="default" sectionFormat="of" derivedCont
ent="RFC8174"/> when, and only when, they appear in all capitals,
as shown here.
</t> </t>
<t indent="0" pn="section-1.6-2">
<t>
The notation used in this memo to (re-)define iCalendar elements is The notation used in this memo to (re-)define iCalendar elements is
the ABNF notation of <xref target='RFC5234'/> as used by the ABNF notation of <xref target="RFC5234" format="default" sectionFo
<xref target='RFC5545'/>. Any syntax rmat="of" derivedContent="RFC5234"/>, as used by
<xref target="RFC5545" format="default" sectionFormat="of" derivedCont
ent="RFC5545"/>. Any syntax
elements shown below that are not explicitly defined in this elements shown below that are not explicitly defined in this
specification come from iCalendar [RFC5545]. specification come from iCalendar [RFC5545].
</t> </t>
</section> </section>
</section> </section>
<section anchor="link_reference_types" numbered="true" removeInRFC="false" t
<section anchor="link_reference_types" oc="include" pn="section-2">
title="LINK Property Reference Types"> <name slugifiedName="name-link-property-reference-typ">LINK Property Refer
<t> ence Types</name>
<t indent="0" pn="section-2-1">
The reference value in the LINK property defined below can take The reference value in the LINK property defined below can take
three forms specified by the VALUE parameter: three forms specified by the VALUE parameter:
<list style='hanging'> </t>
<t hangText="URI:"> <dl newline="false" spacing="normal" indent="3" pn="section-2-2">
<dt pn="section-2-2.1">URI:</dt>
<dd pn="section-2-2.2">
This is a URI referring to the target. This is a URI referring to the target.
</t> </dd>
<t hangText="UID:"> <dt pn="section-2-2.3">UID:</dt>
<dd pn="section-2-2.4">
This allows for linking within a single collection of calendar This allows for linking within a single collection of calendar
components and the value MUST refer to another component components, and the value <bcp14>MUST</bcp14> refer to another compo nent
within the same collection. within the same collection.
</t> </dd>
<t hangText="XML-REFERENCE:"> <dt pn="section-2-2.5">XML-REFERENCE:</dt>
In an XML environment it may be necessary to refer to a <dd pn="section-2-2.6">
In an XML environment, it may be necessary to refer to a
fragment of an external XML artifact. This value is a URI fragment of an external XML artifact. This value is a URI
with an XPointer anchor value. The XPointer is defined in with an XPointer anchor value. The XPointer is defined in
<xref target='W3C.WD-xptr-xpointer-20021219'/> and its <xref target="W3C.WD-xptr-xpointer-20021219" format="default" sectio
use as an anchor is defined in <xref target="W3C.REC-xptr-framework- nFormat="of" derivedContent="W3C.WD-xptr-xpointer-20021219"/>, and its
20030325"/> use as an anchor is defined in <xref target="W3C.REC-xptr-framework-
</t> 20030325" format="default" sectionFormat="of" derivedContent="W3C.REC-xptr-frame
</list> work-20030325"/>.
</t> </dd>
</dl>
<t> <t indent="0" pn="section-2-3">
Note that UID references may need updating on import. An example, Note that UID references may need updating on import. An example
is data to be imported from a file containing VTODO and VEVENT component is data to be imported from a file containing VTODO and VEVENT component
s s,
with a VTODO referring to VEVENT components by UID. When imported with a VTODO referring to VEVENT components by UID. When imported
into a CalDAV system, the VTODO components are typically placed in a dif ferent into a CalDAV system, the VTODO components are typically placed in a dif ferent
collection from the VEVENT components. This would require the collection from the VEVENT components. This would require the
UID reference to be replaced with a URI. UID reference to be replaced with a URI.
</t> </t>
</section> </section>
<section anchor="link_relation_types" numbered="true" removeInRFC="false" to
<section anchor="link_relation_types" c="include" pn="section-3">
title="Link Relation Types"> <name slugifiedName="name-link-relation-types">Link Relation Types</name>
<t> <t indent="0" pn="section-3-1">
<xref target='RFC8288'/> defines two forms of relation type: registered Two forms of relation types are defined in <xref target="RFC8288" format
and ="default" sectionFormat="of" derivedContent="RFC8288"/>: registered and
extension. Registered relation types are added to the Link extension. Registered relation types are added to the "Link
Relations registry as specified in Section 2.1.1 of <xref target='RFC828 Relations" registry, as specified in <xref target="RFC8288" section="2.1
8'/>. .1" sectionFormat="of" format="default" derivedLink="https://rfc-editor.org/rfc/
Extension relation types, defined in Section 2.1.2 of <xref target='RFC8 rfc8288#section-2.1.1" derivedContent="RFC8288"/>.
288'/>, Extension relation types, defined in <xref target="RFC8288" section="2.1
.2" sectionFormat="of" format="default" derivedLink="https://rfc-editor.org/rfc/
rfc8288#section-2.1.2" derivedContent="RFC8288"/>,
are specified as unique URIs that are not registered in the registry. are specified as unique URIs that are not registered in the registry.
</t> </t>
<t indent="0" pn="section-3-2">
<t> The relation types defined in <xref target="linkrel" format="default" se
The relation types defined in <xref target="linkrel" /> will ctionFormat="of" derivedContent="Section 6.1"/> will
be registered with IANA in be registered with IANA in
accordance with the specifications in <xref target='RFC8288'/>. accordance with the specifications in <xref target="RFC8288" format="de fault" sectionFormat="of" derivedContent="RFC8288"/>.
</t> </t>
</section> </section>
<section anchor="new_temporal_reltype_values" numbered="true" removeInRFC="f
<section anchor="new_temporal_reltype_values" alse" toc="include" pn="section-4">
title="New temporal RELTYPE Parameter values"> <name slugifiedName="name-new-temporal-reltype-parame">New Temporal RELTYP
<t> E Parameter Values</name>
<t indent="0" pn="section-4-1">
This section defines the usual temporal relationships This section defines the usual temporal relationships
for use with the RELTYPE parameter defined in for use with the RELTYPE parameter defined in
Section 3.2.15 of <xref target='RFC5545' />: <xref target="RFC5545" section="3.2.15" sectionFormat="of" format="defau
FINISHTOSTART, FINISHTOFINISH, STARTTOFINISH or STARTTOSTART. lt" derivedLink="https://rfc-editor.org/rfc/rfc5545#section-3.2.15" derivedConte
nt="RFC5545"/>:
FINISHTOSTART, FINISHTOFINISH, STARTTOFINISH, or STARTTOSTART.
</t> </t>
<t indent="0" pn="section-4-2">
<t> The <xref target="RFC5545" format="default" sectionFormat="of" derivedCo
The <xref target='RFC5545'/> RELATED-TO property with one or ntent="RFC5545"/> RELATED-TO property with one or
more of these temporal relationships will be present in the more of these temporal relationships will be present in the
predecessor entity and will refer to the successor entity. predecessor entity and will refer to the successor entity.
</t> </t>
<t indent="0" pn="section-4-3">
<t> The GAP parameter (see <xref target="gap" format="default" sectionFormat
The GAP parameter (see <xref target='gap'/>) ="of" derivedContent="Section 6.2"/>)
specifies the lead (a negative value) or lag (a positive value) specifies the lead (a negative value) or lag (a positive value)
time between the predecessor and the successor. time between the predecessor and the successor.
</t> </t>
<t indent="0" pn="section-4-4">
<t>
In the description of each temporal relationship In the description of each temporal relationship
below we refer to Task-A, which contains and controls the relationship, below, we refer to Task-A, which contains and controls the relationship,
and and
Task-B the target of the relationship. This is indicated by Task-B, which is the target of the relationship. This is indicated by
the direction of the arrow in the diagrams below. the direction of the arrows in the diagrams below.
</t> </t>
<t indent="0" pn="section-4-5">
<t> Also, each relationship may be modified by the addition of a
Also each relationship may be modified by the addition of a GAP parameter to the relationship that applies to the targeted
GAP parameter to the relationship which applies to the targeted
component. component.
</t> </t>
<dl newline="false" spacing="normal" indent="3" pn="section-4-6">
<t> <dt pn="section-4-6.1">RELTYPE=FINISHTOSTART:</dt>
<list style="hanging"> <dd pn="section-4-6.2">
<t hangText="RELTYPE=FINISHTOSTART:"> <t indent="0" pn="section-4-6.2.1">
Task-B cannot start until Task-A finishes. Task-B cannot start until Task-A finishes.
For example, when painting is complete, carpet-laying can begin. For example, when painting is complete, carpet laying can begin.
<figure anchor='finishtostart' title='Finish to start relationship'> </t>
<artwork><![CDATA[ <figure anchor="finishtostart" align="left" suppress-title="false" pn=
"figure-1">
<name slugifiedName="name-finish-to-start-relationshi">Finish-to-Sta
rt Relationship</name>
<artwork align="left" pn="section-4-6.2.2.1">
============ ============
| Task-A | | Task-A |
============ ============
| |
V V
============ ============
| Task-B | | Task-B |
============ ============
]]></artwork> </artwork>
</figure> </figure>
</t> </dd>
<dt pn="section-4-6.3">RELTYPE=FINISHTOFINISH:</dt>
<t hangText="RELTYPE=FINISHTOFINISH:"> <dd pn="section-4-6.4">
Task-B can only be completed after Task-A <t indent="0" pn="section-4-6.4.1">Task-B can only be completed after
Task-A
is finished. The related tasks may run in parallel before is finished. The related tasks may run in parallel before
completion. completion.</t>
</t> <t indent="0" pn="section-4-6.4.2">
<t>
For example, in the development of two related pieces of For example, in the development of two related pieces of
software, e.g. the api and the implementation, the design software (e.g., the API and the implementation), the design
of the implementation (B) cannot be completed until the of the implementation (Task-B) cannot be completed until the
design of the api (A) has been completed. design of the API (Task-A) has been completed.
<figure anchor='finishtofinish' title='Finish to finish relationship </t>
'> <figure anchor="finishtofinish" align="left" suppress-title="false" pn
<artwork><![CDATA[ ="figure-2">
<name slugifiedName="name-finish-to-finish-relationsh">Finish-to-Fin
ish Relationship</name>
<artwork align="left" pn="section-4-6.4.3.1">
================== ==================
| Task-A |--+ | Task-A |--+
================== | ================== |
| |
============ | ============ |
| Task-B |<-+ | Task-B |&lt;-+
============ ============
]]></artwork> </artwork>
</figure> </figure>
</t> </dd>
<dt pn="section-4-6.5">RELTYPE=STARTTOFINISH:</dt>
<t hangText="RELTYPE=STARTTOFINISH:"> <dd pn="section-4-6.6">
<t indent="0" pn="section-4-6.6.1">
The start of Task-A (which occurs after Task-B) The start of Task-A (which occurs after Task-B)
controls the finish of Task-B. controls the finish of Task-B.
For example, ticket sales (Task-B) end after the game For example, ticket sales (Task-B) end after the game
starts (Task-A). starts (Task-A).
<figure anchor='starttofinish' title='Start to finish relationship'> </t>
<artwork><![CDATA[ <figure anchor="starttofinish" align="left" suppress-title="false" pn=
"figure-3">
<name slugifiedName="name-start-to-finish-relationshi">Start-to-Fini
sh Relationship</name>
<artwork align="left" pn="section-4-6.6.2.1">
============ ============
+--| Task-A | +--| Task-A |
| ============ | ============
+---------+ +---------+
============ | ============ |
| Task-B |<-+ | Task-B |&lt;-+
============ ============
]]></artwork> </artwork>
</figure> </figure>
</t> </dd>
<dt pn="section-4-6.7">RELTYPE=STARTTOSTART:</dt>
<t hangText="RELTYPE=STARTTOSTART:"> <dd pn="section-4-6.8">
<t indent="0" pn="section-4-6.8.1">
The start of Task-A triggers the start of Task-B, The start of Task-A triggers the start of Task-B,
that is Task-B can start anytime after Task-A starts. that is, Task-B can start anytime after Task-A starts.
<figure anchor='starttostart' title='Start to start relationship'> </t>
<artwork><![CDATA[ <figure anchor="starttostart" align="left" suppress-title="false" pn="
figure-4">
<name slugifiedName="name-start-to-start-relationship">Start-to-Star
t Relationship</name>
<artwork align="left" pn="section-4-6.8.2.1">
============ ============
+--| Task-A | +--| Task-A |
| ============ | ============
| |
| ============ | ============
+->| Task-B | +-&gt;| Task-B |
============ ============
]]></artwork> </artwork>
</figure> </figure>
</t> </dd>
</list> </dl>
</t>
</section> </section>
<section anchor="additional_new_reltype_values" numbered="true" removeInRFC=
<section anchor="additional_new_reltype_values" "false" toc="include" pn="section-5">
title="Additional New RELTYPE Parameter Values"> <name slugifiedName="name-additional-new-reltype-para">Additional New RELT
<t> YPE Parameter Values</name>
<t indent="0" pn="section-5-1">
This section defines the additional relationships below: This section defines the additional relationships below:
</t> </t>
<dl newline="false" spacing="normal" indent="3" pn="section-5-2">
<t> <dt pn="section-5-2.1">RELTYPE=FIRST:</dt>
<list style="hanging"> <dd pn="section-5-2.2">
<t hangText="RELTYPE=FIRST:"> This indicates that the referenced calendar component is the
Indicates that the referenced calendar component is the
first in a series the referencing calendar component is first in a series the referencing calendar component is
part of. part of.
</t> </dd>
<dt pn="section-5-2.3">RELTYPE=NEXT:</dt>
<t hangText="RELTYPE=NEXT:"> <dd pn="section-5-2.4">
Indicates that the referenced calendar component is the This indicates that the referenced calendar component is the
next in a series the referencing calendar component is next in a series the referencing calendar component is
part of. part of.
</t> </dd>
<dt pn="section-5-2.5">RELTYPE=DEPENDS-ON:</dt>
<t hangText="RELTYPE=DEPENDS-ON:"> <dd pn="section-5-2.6">
Indicates that the current calendar component depends on This indicates that the current calendar component depends on
the referenced calendar component in some manner. For example the referenced calendar component in some manner. For example,
a task may be blocked waiting on the other, referenced, task. a task may be blocked waiting on the other, referenced, task.
</t> </dd>
<dt pn="section-5-2.7">RELTYPE=REFID:</dt>
<t hangText="RELTYPE=REFID:"> <dd pn="section-5-2.8">
Establishes a reference from the current component to This establishes a reference from the current component to
components with a REFID property which matches the value components with a REFID property that matches the value
given in the associated RELATED-TO property. given in the associated RELATED-TO property.
</t> </dd>
<dt pn="section-5-2.9">RELTYPE=CONCEPT:</dt>
<t hangText="RELTYPE=CONCEPT:"> <dd pn="section-5-2.10">
Establishes a reference from the current component to This establishes a reference from the current component to
components with a CONCEPT property which matches the value components with a CONCEPT property that matches the value
given in the associated RELATED-TO property. given in the associated RELATED-TO property.
</t> </dd>
</list> </dl>
</t> <t indent="0" pn="section-5-3">
Note that the relationship types of PARENT, CHILD, and SIBLING
<t>
Note that the relationship types of PARENT, CHILD and SIBLING
establish a hierarchical relationship. The new types of FIRST establish a hierarchical relationship. The new types of FIRST
and NEXT are an ordering relationship. and NEXT are an ordering relationship.
</t> </t>
</section> </section>
<section anchor="new_property_parameters" numbered="true" removeInRFC="false
<section anchor="new_property_parameters" " toc="include" pn="section-6">
title="New Property Parameters"> <name slugifiedName="name-new-property-parameters">New Property Parameters
<section anchor="linkrel" </name>
title="Link Relation"> <section anchor="linkrel" numbered="true" removeInRFC="false" toc="include
<t> " pn="section-6.1">
<list style='hanging'> <name slugifiedName="name-link-relation">Link Relation</name>
<t hangText="Parameter name:"> <dl newline="false" spacing="normal" indent="3" pn="section-6.1-1">
<dt pn="section-6.1-1.1">Parameter name:</dt>
<dd pn="section-6.1-1.2">
LINKREL LINKREL
</t> </dd>
<dt pn="section-6.1-1.3">Purpose:</dt>
<t hangText="Purpose:"> <dd pn="section-6.1-1.4">
To specify the relationship of data referenced by a LINK property. This property specifies the relationship of data referenced by a L
</t> INK property.
</dd>
<t hangText="Format Definition:"> <dt pn="section-6.1-1.5">Format Definition:</dt>
<figure> <dd pn="section-6.1-1.6">
<preamble> <t keepWithNext="true" indent="0" pn="section-6.1-1.6.1">
This parameter is defined by the following notation: This parameter is defined by the following notation:
</preamble>
<artwork type="abnf">
linkrelparam = "LINKREL" "="
("SOURCE" ; Link to source of this component
/ DQUOTE uri DQUOTE
/ iana-token) ; Other IANA registered type
</artwork>
</figure>
</t>
<t hangText="Description:">
This parameter MUST be specified on all LINK properties, and
defines the type of reference. This allows programs consuming this
data to automatically scan for references they support. There is n
o default relation type.
</t> </t>
<sourcecode type="abnf" markers="false" pn="section-6.1-1.6.2">
<t> linkrelparam = "LINKREL" "="
In addition to the value defined here any link relation (DQUOTE uri DQUOTE
in the link registry established by <xref target='RFC8288'/>, / iana-token) ; Other IANA registered type
</sourcecode>
</dd>
<dt pn="section-6.1-1.7">Description:</dt>
<dd pn="section-6.1-1.8">
<t indent="0" pn="section-6.1-1.8.1">This parameter <bcp14>MUST</bcp
14> be specified on all LINK properties and
define the type of reference. This allows programs consuming this
data to automatically scan for references they support. There is n
o default
relation type.</t>
<t indent="0" pn="section-6.1-1.8.2">Any link relation
in the link registry established by <xref target="RFC8288" format=
"default" sectionFormat="of" derivedContent="RFC8288"/>,
or new link relations, may be used. or new link relations, may be used.
</t>
<t>
It is expected that link relation types seeing significant It is expected that link relation types seeing significant
usage in calendaring will have the calendaring usage usage in calendaring will have the calendaring usage
described in an RFC. described in an RFC.</t>
</t> </dd>
<dt pn="section-6.1-1.9">LINKREL=latest-version:</dt>
<t hangText="LINKREL=SOURCE:"> <dd pn="section-6.1-1.10">
identifies the source of the event information. This identifies the latest version of the event information.
</t> </dd>
<dt pn="section-6.1-1.11">Registration:</dt>
<t hangText="Registration:"> <dd pn="section-6.1-1.12">
These relation types are registered in <xref target='RFC8288'/> These relation types are registered in <xref target="RFC8288" form
</t> at="default" sectionFormat="of" derivedContent="RFC8288"/>.
</list> </dd>
</t> </dl>
</section> </section>
<section anchor="gap" numbered="true" removeInRFC="false" toc="include" pn
<section anchor="gap" title="Gap"> ="section-6.2">
<t> <name slugifiedName="name-gap">Gap</name>
<list style='hanging'> <dl newline="false" spacing="normal" indent="3" pn="section-6.2-1">
<t hangText="Parameter name:"> <dt pn="section-6.2-1.1">Parameter name:</dt>
<dd pn="section-6.2-1.2">
GAP GAP
</t> </dd>
<dt pn="section-6.2-1.3">Purpose:</dt>
<t hangText="Purpose:"> <dd pn="section-6.2-1.4">
To specify the length of the gap, positive or negative, This property specifies the length of the gap, positive or negativ
e,
between two components with a temporal relationship. between two components with a temporal relationship.
</dd>
<dt pn="section-6.2-1.5">Format Definition:</dt>
<dd pn="section-6.2-1.6">
<t keepWithNext="true" indent="0" pn="section-6.2-1.6.1">
This parameter is defined by the following notation, where
dur-value is defined in <xref target="RFC5545" section="3.3.6"
sectionFormat="of" format="default" derivedLink="https://rfc-editor.org/rfc/rfc
5545#section-3.3.6" derivedContent="RFC5545"/>. :
</t> </t>
<sourcecode type="abnf" markers="false" pn="section-6.2-1.6.2">
<t hangText="Format Definition:">
<figure>
<preamble>
This parameter is defined by the following notation where
dur-value is defined in section 3.3.6 of <xref target="RFC5545
"/>. :
</preamble>
<artwork type="abnf">
gapparam = "GAP" "=" dur-value gapparam = "GAP" "=" dur-value
</artwork> </sourcecode>
</figure> </dd>
</t> <dt pn="section-6.2-1.7">Description:</dt>
<dd pn="section-6.2-1.8">
<t hangText="Description:"> <t indent="0" pn="section-6.2-1.8.1">This parameter <bcp14>MAY</bcp1
This parameter MAY be specified on the RELATED-TO property, and 4> be specified on the RELATED-TO property and
defines the duration of time between the predecessor and successor defines the duration of time between the predecessor and successor
in an interval. When positive it defines the lag time between in an interval. When positive, it defines the lag time between
a task and its logical successor. When negative it defines a task and its logical successor. When negative, it defines
the lead time. the lead time.</t>
</t> <t indent="0" pn="section-6.2-1.8.2">
An example of lag time might be if Task-A is "paint the room"
<t> and Task-B is
An example of lag time might be if task A is "paint the room" "lay the carpets". Then, Task-A may be related to Task-B with
and task B is RELTYPE=FINISHTOSTART with a gap of 1 day -- long enough for the p
"lay the carpets" then task A may be related to task B with aint to
RELTYPE=FINISHTOSTART with a gap of 1 day - long enough for the pa
int to
dry. dry.
<figure anchor='finishtostart-lag' </t>
title='Finish to start relationship with lag'> <figure anchor="finishtostart-lag" align="left" suppress-title="fals
<artwork><![CDATA[ e" pn="figure-5">
<name slugifiedName="name-finish-to-start-relationship">Finish-to-
Start Relationship with Lag</name>
<artwork align="left" pn="section-6.2-1.8.3.1">
==================== ====================
| Paint the room |--+ | paint the room |--+
==================== | ==================== |
|(lag of one day) |(lag of one day)
| |
| =============== | ===================
+->| lay carpet | +-&gt;| lay the carpet |
=============== ===================
]]></artwork> </artwork>
</figure> </figure>
</t> <t indent="0" pn="section-6.2-1.8.4">
For an example of lead time, in constructing a two-story
<t> building, the electrical work must be done before painting.
For an example of lead time, in constructing a two storey However, the painter can move in to the first floor as the
building the electrical work must be done before painting.
However the painter can move in to the first floor as the
electricians move upstairs. electricians move upstairs.
<figure anchor='finishtostart-lead' </t>
title='Finish to start relationship with lead'> <figure anchor="finishtostart-lead" align="left" suppress-title="fal
<artwork><![CDATA[ se" pn="figure-6">
<name slugifiedName="name-finish-to-start-relationship-">Finish-to
-Start Relationship with Lead</name>
<artwork align="left" pn="section-6.2-1.8.5.1">
===================== =====================
| Electrical work |--+ | electrical work |--+
===================== | ===================== |
+-------------+ +-------------+
|(lead of estimated time) |(lead of estimated time)
| ================== | ==================
+->| Painting | +->| painting |
================== ==================
]]></artwork> </artwork>
</figure> </figure>
</t> </dd>
</list> </dl>
</t>
</section> </section>
</section> </section>
<section anchor="new_value_data_types" numbered="true" removeInRFC="false" t
<section anchor="new_value_data_types" oc="include" pn="section-7">
title="New Value Data Types"> <name slugifiedName="name-new-value-data-types">New Value Data Types</name
<t> >
<t indent="0" pn="section-7-1">
This specification defines the following new value types to This specification defines the following new value types to
be used with the VALUE property parameter: be used with the VALUE property parameter:
<list style='hanging'> </t>
<t hangText="UID"> <dl newline="false" spacing="normal" indent="3" pn="section-7-2">
<dt pn="section-7-2.1">UID:</dt>
<dd pn="section-7-2.2">
VALUE=UID indicates that the associated value is the UID for a VALUE=UID indicates that the associated value is the UID for a
component. component.
</t> </dd>
<dt pn="section-7-2.3">XML-REFERENCE:</dt>
<t hangText="XML-REFERENCE"> <dd pn="section-7-2.4">
VALUE=XML-REFERENCE indicates that the associated value VALUE=XML-REFERENCE indicates that the associated value
references an associated XML artifact and is a URI references an associated XML artifact and is a URI
with an XPointer anchor value. The XPointer is defined in with an XPointer anchor value. The XPointer is defined in
<xref target='W3C.WD-xptr-xpointer-20021219'/> and its <xref target="W3C.WD-xptr-xpointer-20021219" format="default" sectio
use as an anchor is defined in <xref target="W3C.REC-xptr-framework- nFormat="of" derivedContent="W3C.WD-xptr-xpointer-20021219"/>, and its
20030325"/>. use as an anchor is defined in <xref target="W3C.REC-xptr-framework-
</t> 20030325" format="default" sectionFormat="of" derivedContent="W3C.REC-xptr-frame
</list> work-20030325"/>.
</t> </dd>
</dl>
</section> </section>
<section anchor="new_properties" numbered="true" removeInRFC="false" toc="in
<section anchor="new_properties" clude" pn="section-8">
title="New Properties"> <name slugifiedName="name-new-properties">New Properties</name>
<section anchor="concept" <section anchor="concept" numbered="true" removeInRFC="false" toc="include
title="Concept"> " pn="section-8.1">
<t> <name slugifiedName="name-concept">Concept</name>
<list style='hanging'> <dl newline="false" spacing="normal" indent="3" pn="section-8.1-1">
<t hangText="Property name:"> <dt pn="section-8.1-1.1">Property name:</dt>
<dd pn="section-8.1-1.2">
CONCEPT CONCEPT
</t> </dd>
<dt pn="section-8.1-1.3">Purpose:</dt>
<t hangText="Purpose:"> <dd pn="section-8.1-1.4">
This property defines the formal categories for a calendar This property defines the formal categories for a calendar
component. component.
</t> </dd>
<dt pn="section-8.1-1.5">Value type:</dt>
<t hangText="Value type:"> <dd pn="section-8.1-1.6">
URI URI
</t> </dd>
<dt pn="section-8.1-1.7">Property Parameters:</dt>
<t hangText="Property Parameters:"> <dd pn="section-8.1-1.8">
IANA, and non-standard parameters can be specified on this propert IANA and non-standard parameters can be specified on this property
y. .
</t> </dd>
<dt pn="section-8.1-1.9">Conformance:</dt>
<t hangText="Conformance:"> <dd pn="section-8.1-1.10">
This property can be specified zero or more times in any This property can be specified zero or more times in any
iCalendar component. iCalendar component.
</t> </dd>
<dt pn="section-8.1-1.11">Description:</dt>
<t hangText="Description:"> <dd pn="section-8.1-1.12">
This property is used to specify formal categories or <t indent="0" pn="section-8.1-1.12.1">This property is used to speci
fy formal categories or
classifications of the calendar component. The values classifications of the calendar component. The values
are useful in searching for a calendar component of a are useful in searching for a calendar component of a
particular type and category. particular type and category.</t>
</t> <t indent="0" pn="section-8.1-1.12.2">This categorization is distinc
t from the more informal
<t>
This categorization is distinct from the more informal
"tagging" of components provided by the existing CATEGORIES "tagging" of components provided by the existing CATEGORIES
property. It is expected that the value of the CONCEPT property. It is expected that the value of the CONCEPT
property will reference an external resource which property will reference an external resource that
provides information about the categorization. provides information about the categorization.</t>
</t> <t indent="0" pn="section-8.1-1.12.3">In addition, a structured URI
value allows for
<t> hierarchical categorization of events.</t>
In addition, a structured URI value allows for <t indent="0" pn="section-8.1-1.12.4">Possible category resources ar
hierarchical categorization of events. e the various proprietary
</t> systems, for example, the Library of Congress, or an open
source of categorization data.</t>
<t> </dd>
Possible category resources are the various proprietary <dt pn="section-8.1-1.13">Format Definition:</dt>
systems, for example Library of Congress, or an open <dd pn="section-8.1-1.14">
source of categorisation data. <t keepWithNext="true" indent="0" pn="section-8.1-1.14.1">
</t>
<t hangText="Format Definition:">
<figure>
<preamble>
This property is defined by the following notation: This property is defined by the following notation:
</preamble> </t>
<sourcecode type="abnf" markers="false" pn="section-8.1-1.14.2">
<artwork>
concept = "CONCEPT" conceptparam ":" concept = "CONCEPT" conceptparam ":"
uri CRLF uri CRLF
conceptparam = *(";" other-param) conceptparam = *(";" other-param)
</sourcecode>
</artwork> </dd>
</figure> <dt pn="section-8.1-1.15">Example:</dt>
</t> <dd pn="section-8.1-1.16">
<t keepWithNext="true" indent="0" pn="section-8.1-1.16.1">
<t hangText="Example:">
<figure>
<preamble>
The following is an example of this property. It points to a The following is an example of this property. It points to a
server acting as the source for the calendar object. server acting as the source for the calendar object.
</preamble>
<artwork>
CONCEPT:https://example.com/event-types/arts/music
</artwork>
</figure>
</t> </t>
</list> <sourcecode markers="false" pn="section-8.1-1.16.2">
</t> CONCEPT:https://example.com/event-types/arts/music
</sourcecode>
</dd>
</dl>
</section> </section>
<section anchor="link" <section anchor="link" numbered="true" removeInRFC="false" toc="include" p
title="Link"> n="section-8.2">
<t> <name slugifiedName="name-link">Link</name>
<list style='hanging'> <dl newline="false" spacing="normal" indent="3" pn="section-8.2-1">
<t hangText="Property name:"> <dt pn="section-8.2-1.1">Property name:</dt>
<dd pn="section-8.2-1.2">
LINK LINK
</t> </dd>
<dt pn="section-8.2-1.3">Purpose:</dt>
<t hangText="Purpose:"> <dd pn="section-8.2-1.4">
This property provides a reference to external information This property provides a reference to external information
related to a component. related to a component.
</t> </dd>
<dt pn="section-8.2-1.5">Value type:</dt>
<t hangText="Value type:"> <dd pn="section-8.2-1.6">
URI, UID or XML-REFERENCE URI, UID, or XML-REFERENCE
</t> </dd>
<dt pn="section-8.2-1.7">Property Parameters:</dt>
<t hangText="Property Parameters:"> <dd pn="section-8.2-1.8">
The VALUE parameter is required. Non-standard, link relation type, The VALUE parameter is required. Non-standard, link relation type,
format type, label and language parameters can also be format type, label, and language parameters can also be
specified on this property. The LABEL parameter specified on this property. The LABEL parameter
is defined in <xref target='RFC7986'/>. is defined in <xref target="RFC7986" format="default" sectionForma
</t> t="of" derivedContent="RFC7986"/>.
</dd>
<t hangText="Conformance:"> <dt pn="section-8.2-1.9">Conformance:</dt>
<dd pn="section-8.2-1.10">
This property can be specified zero or more times in any This property can be specified zero or more times in any
iCalendar component. iCalendar component.
</t> </dd>
<dt pn="section-8.2-1.11">Description:</dt>
<t hangText="Description:"> <dd pn="section-8.2-1.12">
When used in a component the value of this property points to When used in a component, the value of this property points to
additional information related to the component. For example, additional information related to the component. For example,
it may reference the originating web server. it may reference the originating web server.
</t> </dd>
<dt pn="section-8.2-1.13">Format Definition:</dt>
<t hangText="Format Definition:"> <dd pn="section-8.2-1.14">
<figure> <t keepWithNext="true" indent="0" pn="section-8.2-1.14.1">
<preamble>
This property is defined by the following notation: This property is defined by the following notation:
</preamble> </t>
<sourcecode type="abnf" markers="false" pn="section-8.2-1.14.2">
<artwork>
link = "LINK" linkparam ":" link = "LINK" linkparam ":"
( uri / ; for VALUE=XML-REFERENCE ( uri / ; for VALUE=XML-REFERENCE
uri / ; for VALUE=URI uri / ; for VALUE=URI
text ) ; for VALUE=UID text ) ; for VALUE=UID
CRLF CRLF
linkparam = ; the elements herein may appear in any order, linkparam = (";" "VALUE" "=" ("XML-REFERENCE" /
; and the order is not significant. "URI" /
"UID"))
(";" "VALUE" "=" ("XML-REFERENCE" /
"URI" /
"UID"))
1*(";" linkrelparam) 1*(";" linkrelparam)
1*(";" fmttypeparam) 1*(";" fmttypeparam)
1*(";" labelparam) 1*(";" labelparam)
1*(";" languageparam) 1*(";" languageparam)
*(";" other-param) *(";" other-param)
; the elements herein may appear in any order,
</artwork> ; and the order is not significant.
</figure> </sourcecode>
</t> <t indent="0" pn="section-8.2-1.14.3">This property is a serializati
on of the model in
<t> <xref target="RFC8288" format="default" sectionFormat="of" derived
This property is a serialisation of the model in Content="RFC8288"/>, where the link target is
<xref target="RFC8288"/>, where the link target is
carried in the property value, the link context is the carried in the property value, the link context is the
containing calendar entity, and the link relation type containing calendar entity, and the link relation type
and any target attributes are carried in iCalendar property and any target attributes are carried in iCalendar property
parameters. parameters.</t>
</t> <t indent="0" pn="section-8.2-1.14.4">
<t>
The LINK property parameters The LINK property parameters
map to <xref target="RFC8288"/> attributes as follows: map to <xref target="RFC8288" format="default" sectionFormat="of"
derivedContent="RFC8288"/> attributes as follows:</t>
<list style='hanging'> <dl newline="false" spacing="normal" indent="3" pn="section-8.2-1.14
<t hangText="LABEL:"> .5">
Maps to the "title" attribute defined in section 3.4.1 of <xre <dt pn="section-8.2-1.14.5.1">LABEL:</dt>
f target="RFC8288"/>. <dd pn="section-8.2-1.14.5.2">
</t> This parameter maps to the "title" attribute defined in <xref
<t hangText="LANGUAGE:"> target="RFC8288" section="3.4.1" sectionFormat="of" format="default" derivedLink
Maps to the "hreflang" attribute defined in section 3.4.1 of < ="https://rfc-editor.org/rfc/rfc8288#section-3.4.1" derivedContent="RFC8288"/>.
xref target="RFC8288"/>. </dd>
</t> <dt pn="section-8.2-1.14.5.3">LANGUAGE:</dt>
<t hangText="LINKREL:"> <dd pn="section-8.2-1.14.5.4">
Maps to the link relation type defined in section 2.1 of <xref This parameter maps to the "hreflang" attribute defined in <xr
target="RFC8288"/>. ef target="RFC8288" section="3.4.1" sectionFormat="of" format="default" derivedL
</t> ink="https://rfc-editor.org/rfc/rfc8288#section-3.4.1" derivedContent="RFC8288"/
<t hangText="FMTTYPE:"> >.
Maps to the "type" attribute defined in section 3.4.1 of <xref </dd>
target="RFC8288"/>. <dt pn="section-8.2-1.14.5.5">LINKREL:</dt>
</t> <dd pn="section-8.2-1.14.5.6">
</list> This parameter maps to the link relation type defined in <xref
</t> target="RFC8288" section="2.1" sectionFormat="of" format="default" derivedLink=
"https://rfc-editor.org/rfc/rfc8288#section-2.1" derivedContent="RFC8288"/>.
<t> </dd>
There is no mapping for <xref target="RFC8288"/> "title*", <dt pn="section-8.2-1.14.5.7">FMTTYPE:</dt>
"anchor", "rev" or "media". <dd pn="section-8.2-1.14.5.8">
</t> This parameter maps to the "type" attribute defined in <xref t
arget="RFC8288" section="3.4.1" sectionFormat="of" format="default" derivedLink=
<t hangText="Example:"> "https://rfc-editor.org/rfc/rfc8288#section-3.4.1" derivedContent="RFC8288"/>.
<figure> </dd>
<preamble> </dl>
The following is an example of this property which <t indent="0" pn="section-8.2-1.14.6">There is no mapping for "title
*",
"anchor", "rev", or "media" <xref target="RFC8288" format="default
" sectionFormat="of" derivedContent="RFC8288"/>.</t>
</dd>
<dt pn="section-8.2-1.15">Example:</dt>
<dd pn="section-8.2-1.16">
<t keepWithNext="true" indent="0" pn="section-8.2-1.16.1">
The following is an example of this property, which
provides a reference to the source for the calendar object. provides a reference to the source for the calendar object.
</preamble> </t>
<sourcecode markers="false" pn="section-8.2-1.16.2">
<artwork>
LINK;LINKREL=SOURCE;LABEL=Venue;VALUE=URI: LINK;LINKREL=SOURCE;LABEL=Venue;VALUE=URI:
https://example.com/events https://example.com/events
</artwork> </sourcecode>
</figure> </dd>
</t> <dt pn="section-8.2-1.17">Example:</dt>
<dd pn="section-8.2-1.18">
<t hangText="Example:"> <t keepWithNext="true" indent="0" pn="section-8.2-1.18.1">
<figure> The following is an example of this property, which
<preamble>
The following is an example of this property which
provides a reference to an entity from which this one provides a reference to an entity from which this one
was derived. The link relation is a vendor defined value. was derived. The link relation is a vendor-defined value.
</preamble> </t>
<sourcecode markers="false" pn="section-8.2-1.18.2">
<artwork>
LINK;LINKREL="https://example.com/linkrel/derivedFrom"; LINK;LINKREL="https://example.com/linkrel/derivedFrom";
VALUE=URI: VALUE=URI:
https://example.com/tasks/01234567-abcd1234.ics https://example.com/tasks/01234567-abcd1234.ics
</artwork> </sourcecode>
</figure> </dd>
</t> <dt pn="section-8.2-1.19">Example:</dt>
<dd pn="section-8.2-1.20">
<t hangText="Example:"> <t keepWithNext="true" indent="0" pn="section-8.2-1.20.1">
<figure> The following is an example of this property, which
<preamble>
The following is an example of this property which
provides a reference to a fragment of an XML document. provides a reference to a fragment of an XML document.
The link relation is a vendor defined value. The link relation is a vendor-defined value.
</preamble> </t>
<sourcecode markers="false" pn="section-8.2-1.20.2">
<artwork>
LINK;LINKREL="https://example.com/linkrel/costStructure"; LINK;LINKREL="https://example.com/linkrel/costStructure";
VALUE=XML-REFERENCE: VALUE=XML-REFERENCE:
https://example.com/xmlDocs/bidFramework.xml https://example.com/xmlDocs/bidFramework.xml
#xpointer(descendant::CostStruc/range-to( #xpointer(descendant::CostStruc/range-to(
following::CostStrucEND[1])) following::CostStrucEND[1]))
</artwork> </sourcecode>
</figure> </dd>
</t> </dl>
</list>
</t>
</section> </section>
<section anchor="refid" numbered="true" removeInRFC="false" toc="include"
<section anchor="refid" pn="section-8.3">
title="Refid"> <name slugifiedName="name-refid">Refid</name>
<t> <dl newline="false" spacing="normal" indent="3" pn="section-8.3-1">
<list style='hanging'> <dt pn="section-8.3-1.1">Property name:</dt>
<t hangText="Property name:"> <dd pn="section-8.3-1.2">
REFID REFID
</t> </dd>
<dt pn="section-8.3-1.3">Purpose:</dt>
<t hangText="Purpose:"> <dd pn="section-8.3-1.4">
This property value acts as a key for associated This property value acts as a key for associated
iCalendar entities. iCalendar entities.
</t> </dd>
<dt pn="section-8.3-1.5">Value type:</dt>
<t hangText="Value type:"> <dd pn="section-8.3-1.6">
TEXT TEXT
</t> </dd>
<dt pn="section-8.3-1.7">Property Parameters:</dt>
<t hangText="Property Parameters:"> <dd pn="section-8.3-1.8">
Non-standard parameters can be specified on this property. Non-standard parameters can be specified on this property.
</t> </dd>
<dt pn="section-8.3-1.9">Conformance:</dt>
<t hangText="Conformance:"> <dd pn="section-8.3-1.10">
This property can be specified zero or more times in any This property can be specified zero or more times in any
iCalendar component. iCalendar component.
</t> </dd>
<dt pn="section-8.3-1.11">Description:</dt>
<t hangText="Description:"> <dd pn="section-8.3-1.12">
The value of this property is free-form text that The value of this property is free-form text that
creates an identifier for associated components. All components creates an identifier for associated components. All components
that use the same REFID value are associated through that value that use the same REFID value are associated through that value
and can be located or retrieved as a group. For example, all of and can be located or retrieved as a group. For example, all of
the events in a travel itinerary would have the same REFID value, the events in a travel itinerary would have the same REFID value,
so as to be grouped together. so as to be grouped together.
</t> </dd>
<dt pn="section-8.3-1.13">Format Definition:</dt>
<t hangText="Format Definition:"> <dd pn="section-8.3-1.14">
<figure> <t keepWithNext="true" indent="0" pn="section-8.3-1.14.1">
<preamble>
This property is defined by the following notation: This property is defined by the following notation:
</preamble> </t>
<sourcecode type="abnf" markers="false" pn="section-8.3-1.14.2">
<artwork>
refid = "REFID" refidparam ":" text CRLF refid = "REFID" refidparam ":" text CRLF
refidparam = *(";" other-param) refidparam = *(";" other-param)
</artwork> </sourcecode>
</figure> </dd>
</t> <dt pn="section-8.3-1.15">Example:</dt>
<dd pn="section-8.3-1.16">
<t> <t keepWithNext="true" indent="0" pn="section-8.3-1.16.1">
The current link registry
</t>
<t hangText="Example:">
<figure>
<preamble>
The following is an example of this property. The following is an example of this property.
</preamble>
<artwork>
REFID:itinerary-2014-11-17
</artwork>
</figure>
</t> </t>
</list> <sourcecode markers="false" pn="section-8.3-1.16.2">
</t> REFID:itinerary-2014-11-17
</sourcecode>
</dd>
</dl>
</section> </section>
</section> </section>
<section anchor="updates_to_rfc_5545" numbered="true" removeInRFC="false" to
<section anchor="updates_to_rfc_5545" c="include" pn="section-9">
title="Updates to RFC 5545"> <name slugifiedName="name-updates-to-rfc-5545">Updates to RFC 5545</name>
<t> <t indent="0" pn="section-9-1">
This specification updates the RELATED-TO property defined This specification updates the RELATED-TO property defined
in Section 3.8.4.5 of <xref target='RFC5545'/>. The contents in <xref target="RFC5545" section="3.8.4.5" sectionFormat="of" format="d
of <xref target="related-to" /> replace that section. efault" derivedLink="https://rfc-editor.org/rfc/rfc5545#section-3.8.4.5" derived
Content="RFC5545"/>. The contents
of <xref target="related-to" format="default" sectionFormat="of" derived
Content="Section 9.1"/> replace that section.
</t> </t>
<t indent="0" pn="section-9-2">
<t>
The RELTYPE parameter is extended to take new values defining The RELTYPE parameter is extended to take new values defining
temporal relationships, a GAP parameter is defined to provide lead temporal relationships, a GAP parameter is defined to provide lead
and lag values, and RELATED-TO is extended to allow URI values. and lag values, and RELATED-TO is extended to allow URI values.
These changes allow the RELATED-TO property to define a richer set of These changes allow the RELATED-TO property to define a richer set of
relationships useful for project management. relationships useful for project management.
</t> </t>
<section anchor="related-to" numbered="true" removeInRFC="false" toc="incl
<section anchor="related-to" ude" pn="section-9.1">
title="RELATED-TO"> <name slugifiedName="name-related-to">RELATED-TO</name>
<t> <dl newline="false" spacing="normal" indent="3" pn="section-9.1-1">
<list style='hanging'> <dt pn="section-9.1-1.1">Property name:</dt>
<t hangText="Property Name:"> <dd pn="section-9.1-1.2">
RELATED-TO RELATED-TO
</t> </dd>
<dt pn="section-9.1-1.3">Purpose:</dt>
<t hangText="Purpose:"> <dd pn="section-9.1-1.4">
This property is used to represent a relationship or This property is used to represent a relationship or
reference between one calendar component and another. The definiti on reference between one calendar component and another. The definiti on
here extends the definition in Section 3.8.4.5 of here extends the definition in <xref target="RFC5545" section="3.8
<xref target='RFC5545'/> by allowing URI or UID values and a GAP p .4.5" sectionFormat="of" format="default" derivedLink="https://rfc-editor.org/rf
arameter. c/rfc5545#section-3.8.4.5" derivedContent="RFC5545"/> by allowing URI or UID val
</t> ues and a GAP parameter.
</dd>
<t hangText="Value Type:"> <dt pn="section-9.1-1.5">Value Type:</dt>
URI, UID or TEXT <dd pn="section-9.1-1.6">
</t> URI, UID, or TEXT
</dd>
<t hangText="Property Parameters:"> <dt pn="section-9.1-1.7">Property Parameters:</dt>
Relationship type, IANA and non-standard <dd pn="section-9.1-1.8">
Relationship type, IANA, and non-standard
property parameters can be specified on this property. property parameters can be specified on this property.
</t> </dd>
<dt pn="section-9.1-1.9">Conformance:</dt>
<t hangText="Conformance:"> <dd pn="section-9.1-1.10">
This property MAY be specified in any iCalendar component. This property <bcp14>MAY</bcp14> be specified in any iCalendar com
</t> ponent.
</dd>
<t hangText="Description:"> <dt pn="section-9.1-1.11">Description:</dt>
By default or when VALUE=UID is specified, the property value <dd pn="section-9.1-1.12">
<t indent="0" pn="section-9.1-1.12.1">By default or when VALUE=UID i
s specified, the property value
consists of the persistent, globally consists of the persistent, globally
unique identifier of another calendar component. This value would unique identifier of another calendar component. This value would
be represented in a calendar component by the "UID" property. be represented in a calendar component by the UID property.</t>
</t> <t indent="0" pn="section-9.1-1.12.2">By default, the property value
points to another calendar
<t>
By default, the property value points to another calendar
component that has a PARENT relationship to the referencing component that has a PARENT relationship to the referencing
object. The "RELTYPE" property parameter is used to either object. The RELTYPE property parameter is used to either
explicitly state the default PARENT relationship type to the explicitly state the default PARENT relationship type to the
referenced calendar component or to override the default PARENT referenced calendar component or to override the default PARENT
relationship type and specify either a CHILD or SIBLING relationship type and specify either a CHILD or SIBLING
relationship or a temporal relationship. relationship or a temporal relationship.</t>
</t> <t indent="0" pn="section-9.1-1.12.3">The PARENT relationship indica
tes that the calendar
<t>
The PARENT relationship indicates that the calendar
component is a subordinate of the referenced calendar component. component is a subordinate of the referenced calendar component.
The CHILD relationship indicates that the calendar component is a The CHILD relationship indicates that the calendar component is a
superior of the referenced calendar component. The SIBLING superior of the referenced calendar component. The SIBLING
relationship indicates that the calendar component is a peer of relationship indicates that the calendar component is a peer of
the referenced calendar component. the referenced calendar component.</t>
</t> <t indent="0" pn="section-9.1-1.12.4">To preserve backwards compatib
ility, the value type <bcp14>MUST</bcp14>
<t> be UID when the PARENT, SIBLING, or CHILD
To preserve backwards compatibility the value type MUST relationships are specified.</t>
be UID when the PARENT, SIBLING or CHILD <t indent="0" pn="section-9.1-1.12.5">The FINISHTOSTART, FINISHTOFIN
relationships are specified. ISH, STARTTOFINISH, or STARTTOSTART
</t> relationships define temporal relationships, as specified in the
RELTYPE parameter definition.</t>
<t> <t indent="0" pn="section-9.1-1.12.6">The FIRST and NEXT define orde
The FINISHTOSTART, FINISHTOFINISH, STARTTOFINISH or STARTTOSTART ring relationships between
relationships define temporal relationships as specified in the calendar components.</t>
reltype parameter definition. <t indent="0" pn="section-9.1-1.12.7">The DEPENDS-ON relationship in
</t> dicates that the current
<t>
The FIRST and NEXT define ordering relationships between
calendar components.
</t>
<t>
The DEPENDS-ON relationship indicates that the current
calendar component depends on calendar component depends on
the referenced calendar component in some manner. For example the referenced calendar component in some manner. For example,
a task may be blocked waiting on the other, referenced, task. a task may be blocked waiting on the other, referenced, task.</t>
</t> <t indent="0" pn="section-9.1-1.12.8">The REFID and CONCEPT relation
ships establish a reference
<t> from the current component to the referenced component.</t>
The REFID and CONCEPT relationships establish a reference <t indent="0" pn="section-9.1-1.12.9">Changes to a calendar componen
from the current component to the referenced component. t referenced by this property can
</t>
<t>
Changes to a calendar component referenced by this property can
have an implicit impact on the related calendar component. For have an implicit impact on the related calendar component. For
example, if a group event changes its start or end date or time, example, if a group event changes its start or end date or time,
then the related, dependent events will need to have their start then the related, dependent events will need to have their start
and end dates changed in a corresponding way. Similarly, if a and end dates and times changed in a corresponding way. Similarly
PARENT calendar component is cancelled or deleted, then there is , if a
PARENT calendar component is canceled or deleted, then there is
an implied impact to the related CHILD calendar components. This an implied impact to the related CHILD calendar components. This
property is intended only to provide information on the property is intended only to provide information on the
relationship of calendar components. relationship of calendar components.</t>
</t> <t indent="0" pn="section-9.1-1.12.10">Deletion of the target compon
ent, for example, the target
<t> of a FIRST, NEXT, or temporal relationship, can result in broken
Deletion of the target component, for example the target links.</t>
of a FIRST, NEXT or temporal relationship can result in broken <t indent="0" pn="section-9.1-1.12.11">It is up to the target calend
links. ar system to maintain any
</t> property implications of these relationships.</t>
</dd>
<t> <dt pn="section-9.1-1.13">Format Definition:</dt>
It is up to the target calendar system to maintain any <dd pn="section-9.1-1.14">
property implications of these relationships. <t keepWithNext="true" indent="0" pn="section-9.1-1.14.1">
</t>
<t hangText="Format Definition:">
<figure>
<preamble>
This property is defined by the following notation: This property is defined by the following notation:
</preamble> </t>
<sourcecode type="abnf" markers="false" pn="section-9.1-1.14.2">
<artwork>
related = "RELATED-TO" relparam ":" related = "RELATED-TO" relparam ":"
( text / ; for VALUE=UID ( text / ; for VALUE=UID
uri / ; for VALUE=URI uri / ; for VALUE=URI
text ) ; for VALUE=TEXT or default text ) ; for VALUE=TEXT or default
CRLF CRLF
relparam = ; the elements herein may appear in any order, relparam = ; the elements herein may appear in any order,
; and the order is not significant. ; and the order is not significant.
[";" "VALUE" "=" ("UID" / [";" "VALUE" "=" ("UID" /
"URI" / "URI" /
"TEXT")] "TEXT")]
[";" reltypeparam] [";" reltypeparam]
[";" gapparam] [";" gapparam]
*(";" other-param) *(";" other-param)
</artwork> </sourcecode>
</figure> </dd>
</t> <dt pn="section-9.1-1.15">Example:</dt>
<dd pn="section-9.1-1.16">
<t hangText="Example:"> <t keepWithNext="true" indent="0" pn="section-9.1-1.16.1">
<figure>
<preamble>
The following are examples of this property. The following are examples of this property.
</preamble> </t>
<sourcecode markers="false" pn="section-9.1-1.16.2">
<artwork>
RELATED-TO:jsmith.part7.19960817T083000.xyzMail@example.com RELATED-TO:jsmith.part7.19960817T083000.xyzMail@example.com
RELATED-TO:19960401-080045-4000F192713-0052@example.com RELATED-TO:19960401-080045-4000F192713-0052@example.com
RELATED-TO;VALUE=URI;RELTYPE=STARTTOFINISH: RELATED-TO;VALUE=URI;RELTYPE=STARTTOFINISH:
https://example.com/caldav/user/jb/cal/ https://example.com/caldav/user/jb/cal/
19960401-080045-4000F192713.ics 19960401-080045-4000F192713.ics
</artwork> </sourcecode>
</figure> </dd>
</t> </dl>
</list>
</t>
</section> </section>
</section> </section>
<section numbered="true" removeInRFC="false" toc="include" pn="section-10">
<section title='Security Considerations'> <name slugifiedName="name-security-considerations">Security Considerations
<t> </name>
All of the security considerations of section 7 pf <t indent="0" pn="section-10-1">
<xref target='RFC5545'/> apply to this specification. All of the security considerations of <xref target="RFC5545" section="7"
sectionFormat="of" format="default" derivedLink="https://rfc-editor.org/rfc/rfc
5545#section-7" derivedContent="RFC5545"/> apply to this specification.
</t> </t>
<t indent="0" pn="section-10-2">
<t>
Applications using the LINK property need to be aware of the risks Applications using the LINK property need to be aware of the risks
entailed in using the URIs provided as values. See section 7 of entailed in using the URIs provided as values. See <xref target="RFC3986"
<xref target='RFC3986'/> for section="7" sectionFormat="of" format="default" derivedLink="https://rfc-editor
.org/rfc/rfc3986#section-7" derivedContent="RFC3986"/> for
a discussion of the security considerations relating to URIs. a discussion of the security considerations relating to URIs.
</t> </t>
<t indent="0" pn="section-10-3">
<t> In particular, note Section <xref target="RFC3986" section="7.1" section
In particular note section 7.1 "Reliability and Consistency" of Format="bare" format="default" derivedLink="https://rfc-editor.org/rfc/rfc3986#s
<xref target='RFC3986'/> which points out the lack of a stability ection-7.1" derivedContent="RFC3986">Reliability and Consistency</xref> of <xref
target="RFC3986" format="default" sectionFormat="of" derivedContent="RFC3986"/>
,
which points out the lack of a stability
guarantee for referenced resources. guarantee for referenced resources.
</t> </t>
<t indent="0" pn="section-10-4">
<t> When the value is an XML-REFERENCE type, the targeted data is an XML doc
When the value is an XML-REFERENCE type the targeted data is an XML docu ument
ment
or portion thereof. Consumers need to be aware of the security issues or portion thereof. Consumers need to be aware of the security issues
related to XML processing - in particular those related to XML entities. related to XML processing -- in particular, those related to XML entitie
See <xref target='RFC4918'/> - Section 20.6. Additionally note that s.
See <xref target="RFC4918" sectionFormat="of" section="20.6" format="def
ault" derivedLink="https://rfc-editor.org/rfc/rfc4918#section-20.6" derivedConte
nt="RFC4918"/>. Additionally, note that
the reference may be invalid or become so over time. the reference may be invalid or become so over time.
</t> </t>
<t> <t indent="0" pn="section-10-5">
The CONCEPT and redefined RELATED-TO property have The CONCEPT and redefined RELATED-TO properties have
the same issues in that values may be URIs. the same issues in that values may be URIs.
</t> </t>
<t> <t indent="0" pn="section-10-6">
Extremely large values for the GAP parameter may lead to Extremely large values for the GAP parameter may lead to
unexpected behavior. unexpected behavior.
</t> </t>
</section> </section>
<section anchor="iana_considerations" numbered="true" removeInRFC="false" to
<section anchor="iana_considerations" title='IANA Considerations'> c="include" pn="section-11">
<section anchor="property_registrations" <name slugifiedName="name-iana-considerations">IANA Considerations</name>
title="iCalendar Property Registrations" > <section anchor="property_registrations" numbered="true" removeInRFC="fals
<t> e" toc="include" pn="section-11.1">
<name slugifiedName="name-icalendar-property-registra">iCalendar Propert
y Registrations</name>
<t indent="0" pn="section-11.1-1">
The following iCalendar property names have been added to The following iCalendar property names have been added to
the iCalendar Properties Registry defined in Section 8.3.2 of the iCalendar "Properties" registry defined in <xref target="RFC5545"
<xref target='RFC5545'/>. IANA has also added a section="8.3.2" sectionFormat="of" format="default" derivedLink="https://rfc-edi
reference to this document where the properties originally defined in tor.org/rfc/rfc5545#section-8.3.2" derivedContent="RFC5545"/>. IANA has also ad
<xref target='RFC5545'/> have been updated by this document. ded a
reference to this document, where the properties originally defined in
<xref target="RFC5545" format="default" sectionFormat="of" derivedCont
ent="RFC5545"/> have been updated by this document.
</t> </t>
<table align="center" pn="table-1">
<texttable> <thead>
<ttcol align="left">Property</ttcol> <tr>
<ttcol align="left">Status</ttcol> <th align="left" colspan="1" rowspan="1">Property</th>
<ttcol align="left">Reference</ttcol> <th align="left" colspan="1" rowspan="1">Status</th>
<th align="left" colspan="1" rowspan="1">Reference</th>
<c>CONCEPT</c> </tr>
<c>Current</c> </thead>
<c><xref target="concept"/></c> <tbody>
<tr>
<c>LINK</c> <td align="left" colspan="1" rowspan="1">CONCEPT</td>
<c>Current</c> <td align="left" colspan="1" rowspan="1">Current</td>
<c><xref target="link"/></c> <td align="left" colspan="1" rowspan="1">
<xref target="concept" format="default" sectionFormat="of" deriv
<c>REFID</c> edContent="Section 8.1"/></td>
<c>Current</c> </tr>
<c><xref target="refid"/></c> <tr>
<td align="left" colspan="1" rowspan="1">LINK</td>
<c>RELATED-TO</c> <td align="left" colspan="1" rowspan="1">Current</td>
<c>Current</c> <td align="left" colspan="1" rowspan="1">
<c><xref target='RFC5545'/>, <xref target="related-to"/></c> <xref target="link" format="default" sectionFormat="of" derivedC
</texttable> ontent="Section 8.2"/></td>
</tr>
<tr>
<td align="left" colspan="1" rowspan="1">REFID</td>
<td align="left" colspan="1" rowspan="1">Current</td>
<td align="left" colspan="1" rowspan="1">
<xref target="refid" format="default" sectionFormat="of" derived
Content="Section 8.3"/></td>
</tr>
<tr>
<td align="left" colspan="1" rowspan="1">RELATED-TO</td>
<td align="left" colspan="1" rowspan="1">Current</td>
<td align="left" colspan="1" rowspan="1">
<xref target="RFC5545" section="3.8.4.5" sectionFormat="comma" f
ormat="default" derivedLink="https://rfc-editor.org/rfc/rfc5545#section-3.8.4.5"
derivedContent="RFC5545"/>; RFC 9253, <xref target="related-to" format="default
" sectionFormat="of" derivedContent="Section 9.1"/></td>
</tr>
</tbody>
</table>
</section> </section>
<section anchor="property_parameter_registrations" numbered="true" removeI
<section anchor="property_parameter_registrations" nRFC="false" toc="include" pn="section-11.2">
title="iCalendar Property Parameter Registrations" > <name slugifiedName="name-icalendar-property-paramete">iCalendar Propert
<t> y Parameter Registrations</name>
<t indent="0" pn="section-11.2-1">
The following iCalendar property parameter names have been added to The following iCalendar property parameter names have been added to
the iCalendar Parameters Registry defined in Section 8.3.3 of the iCalendar "Parameters" registry defined in <xref target="RFC5545"
<xref target='RFC5545'/>. section="8.3.3" sectionFormat="of" format="default" derivedLink="https://rfc-edi
tor.org/rfc/rfc5545#section-8.3.3" derivedContent="RFC5545"/>.
</t> </t>
<table align="center" pn="table-2">
<texttable> <thead>
<ttcol align="left">Parameter</ttcol> <tr>
<ttcol align="left">Status</ttcol> <th align="left" colspan="1" rowspan="1">Parameter</th>
<ttcol align="left">Reference</ttcol> <th align="left" colspan="1" rowspan="1">Status</th>
<th align="left" colspan="1" rowspan="1">Reference</th>
<c>GAP</c> </tr>
<c>Current</c> </thead>
<c><xref target="gap"/></c> <tbody>
<tr>
<c>LINKREL</c> <td align="left" colspan="1" rowspan="1">GAP</td>
<c>Current</c> <td align="left" colspan="1" rowspan="1">Current</td>
<c><xref target="linkrel"/></c> <td align="left" colspan="1" rowspan="1">
</texttable> <xref target="gap" format="default" sectionFormat="of" derivedCo
ntent="Section 6.2"/></td>
</tr>
<tr>
<td align="left" colspan="1" rowspan="1">LINKREL</td>
<td align="left" colspan="1" rowspan="1">Current</td>
<td align="left" colspan="1" rowspan="1">
<xref target="linkrel" format="default" sectionFormat="of" deriv
edContent="Section 6.1"/></td>
</tr>
</tbody>
</table>
</section> </section>
<section anchor="value_data_types_registrations" numbered="true" removeInR
<section anchor="value_data_types_registrations" FC="false" toc="include" pn="section-11.3">
title="iCalendar Value Data Type Registrations" > <name slugifiedName="name-icalendar-value-data-type-r">iCalendar Value D
<t> ata Type Registrations</name>
<t indent="0" pn="section-11.3-1">
The following iCalendar property parameter names have been added to The following iCalendar property parameter names have been added to
the iCalendar Value Data Types Registry defined in Section 8.3.4 of the iCalendar "Value Data Types" registry defined in <xref target="RFC
<xref target='RFC5545'/>. 5545" section="8.3.4" sectionFormat="of" format="default" derivedLink="https://r
fc-editor.org/rfc/rfc5545#section-8.3.4" derivedContent="RFC5545"/>.
</t> </t>
<table align="center" pn="table-3">
<texttable> <thead>
<ttcol align="left">Value Data Type</ttcol> <tr>
<ttcol align="left">Status</ttcol> <th align="left" colspan="1" rowspan="1">Value Data Type</th>
<ttcol align="left">Reference</ttcol> <th align="left" colspan="1" rowspan="1">Status</th>
<th align="left" colspan="1" rowspan="1">Reference</th>
<c>XML-REFERENCE</c> </tr>
<c>Current</c> </thead>
<c><xref target="new_value_data_types"/></c> <tbody>
<tr>
<c>UID</c> <td align="left" colspan="1" rowspan="1">XML-REFERENCE</td>
<c>Current</c> <td align="left" colspan="1" rowspan="1">Current</td>
<c><xref target="new_value_data_types"/></c> <td align="left" colspan="1" rowspan="1">
</texttable> <xref target="new_value_data_types" format="default" sectionForm
at="of" derivedContent="Section 7"/></td>
</tr>
<tr>
<td align="left" colspan="1" rowspan="1">UID</td>
<td align="left" colspan="1" rowspan="1">Current</td>
<td align="left" colspan="1" rowspan="1">
<xref target="new_value_data_types" format="default" sectionForm
at="of" derivedContent="Section 7"/></td>
</tr>
</tbody>
</table>
</section> </section>
<section anchor="reltype_value_registrations" numbered="true" removeInRFC=
<section anchor="reltype_value_registrations" "false" toc="include" pn="section-11.4">
title="iCalendar RELTYPE Value Registrations" > <name slugifiedName="name-icalendar-reltype-value-reg">iCalendar RELTYPE
<t> Value Registrations</name>
<t indent="0" pn="section-11.4-1">
The following iCalendar "RELTYPE" values have been added to The following iCalendar "RELTYPE" values have been added to
the iCalendar Relationship Types Registry defined in Section 8.3.8 of the iCalendar "Relationship Types" registry defined in <xref target="R
<xref target='RFC5545'/>. FC5545" section="8.3.8" sectionFormat="of" format="default" derivedLink="https:/
</t> /rfc-editor.org/rfc/rfc5545#section-8.3.8" derivedContent="RFC5545"/>.
<texttable>
<ttcol align="left">Relationship Type</ttcol>
<ttcol align="left">Status</ttcol>
<ttcol align="left">Reference</ttcol>
<c>CONCEPT</c>
<c>Current</c>
<c><xref target="additional_new_reltype_values"/></c>
<c>DEPENDS-ON</c>
<c>Current</c>
<c><xref target="additional_new_reltype_values"/></c>
<c>FINISHTOFINISH</c>
<c>Current</c>
<c><xref target="new_temporal_reltype_values"/></c>
<c>FINISHTOSTART</c>
<c>Current</c>
<c><xref target="new_temporal_reltype_values"/></c>
<c>FIRST</c>
<c>Current</c>
<c><xref target="additional_new_reltype_values"/></c>
<c>NEXT</c>
<c>Current</c>
<c><xref target="additional_new_reltype_values"/></c>
<c>REFID</c>
<c>Current</c>
<c><xref target="additional_new_reltype_values"/></c>
<c>STARTTOFINISH</c>
<c>Current</c>
<c><xref target="new_temporal_reltype_values"/></c>
<c>STARTTOSTART</c>
<c>Current</c>
<c><xref target="new_temporal_reltype_values"/></c>
</texttable>
</section>
<section anchor="new_linkrel_registration"
title="New Reference Type Registration">
<t>
The following link relation values have been added to
the Reference Types Registry defined in Section 6.2.2 of
<xref target='RFC8288'/>.
</t> </t>
<table align="center" pn="table-4">
<texttable> <thead>
<ttcol align="left">Name</ttcol> <tr>
<ttcol align="left">Status</ttcol> <th align="left" colspan="1" rowspan="1">Relationship Type</th>
<ttcol align="left">Reference</ttcol> <th align="left" colspan="1" rowspan="1">Status</th>
<th align="left" colspan="1" rowspan="1">Reference</th>
<c>SOURCE</c> </tr>
<c>Current</c> </thead>
<c><xref target="linkrel"/></c> <tbody>
</texttable> <tr>
<td align="left" colspan="1" rowspan="1">CONCEPT</td>
<td align="left" colspan="1" rowspan="1">Current</td>
<td align="left" colspan="1" rowspan="1">
<xref target="additional_new_reltype_values" format="default" se
ctionFormat="of" derivedContent="Section 5"/></td>
</tr>
<tr>
<td align="left" colspan="1" rowspan="1">DEPENDS-ON</td>
<td align="left" colspan="1" rowspan="1">Current</td>
<td align="left" colspan="1" rowspan="1">
<xref target="additional_new_reltype_values" format="default" se
ctionFormat="of" derivedContent="Section 5"/></td>
</tr>
<tr>
<td align="left" colspan="1" rowspan="1">FINISHTOFINISH</td>
<td align="left" colspan="1" rowspan="1">Current</td>
<td align="left" colspan="1" rowspan="1">
<xref target="new_temporal_reltype_values" format="default" sect
ionFormat="of" derivedContent="Section 4"/></td>
</tr>
<tr>
<td align="left" colspan="1" rowspan="1">FINISHTOSTART</td>
<td align="left" colspan="1" rowspan="1">Current</td>
<td align="left" colspan="1" rowspan="1">
<xref target="new_temporal_reltype_values" format="default" sect
ionFormat="of" derivedContent="Section 4"/></td>
</tr>
<tr>
<td align="left" colspan="1" rowspan="1">FIRST</td>
<td align="left" colspan="1" rowspan="1">Current</td>
<td align="left" colspan="1" rowspan="1">
<xref target="additional_new_reltype_values" format="default" se
ctionFormat="of" derivedContent="Section 5"/></td>
</tr>
<tr>
<td align="left" colspan="1" rowspan="1">NEXT</td>
<td align="left" colspan="1" rowspan="1">Current</td>
<td align="left" colspan="1" rowspan="1">
<xref target="additional_new_reltype_values" format="default" se
ctionFormat="of" derivedContent="Section 5"/></td>
</tr>
<tr>
<td align="left" colspan="1" rowspan="1">REFID</td>
<td align="left" colspan="1" rowspan="1">Current</td>
<td align="left" colspan="1" rowspan="1">
<xref target="additional_new_reltype_values" format="default" se
ctionFormat="of" derivedContent="Section 5"/></td>
</tr>
<tr>
<td align="left" colspan="1" rowspan="1">STARTTOFINISH</td>
<td align="left" colspan="1" rowspan="1">Current</td>
<td align="left" colspan="1" rowspan="1">
<xref target="new_temporal_reltype_values" format="default" sect
ionFormat="of" derivedContent="Section 4"/></td>
</tr>
<tr>
<td align="left" colspan="1" rowspan="1">STARTTOSTART</td>
<td align="left" colspan="1" rowspan="1">Current</td>
<td align="left" colspan="1" rowspan="1">
<xref target="new_temporal_reltype_values" format="default" sect
ionFormat="of" derivedContent="Section 4"/></td>
</tr>
</tbody>
</table>
</section> </section>
</section> </section>
</middle>
<section title="Acknowledgements"> <back>
<t> <references pn="section-12">
<name slugifiedName="name-references">References</name>
<references pn="section-12.1">
<name slugifiedName="name-normative-references">Normative References</na
me>
<reference anchor="RFC2119" target="https://www.rfc-editor.org/info/rfc2
119" quoteTitle="true" derivedAnchor="RFC2119">
<front>
<title>Key words for use in RFCs to Indicate Requirement Levels</tit
le>
<author fullname="S. Bradner" initials="S" surname="Bradner"/>
<date month="March" year="1997"/>
<abstract>
<t indent="0">In many standards track documents several words are
used to signify the requirements in the specification. These words are often ca
pitalized. This document defines these words as they should be interpreted in I
ETF documents. This document specifies an Internet Best Current Practices for t
he Internet Community, and requests discussion and suggestions for improvements.
</t>
</abstract>
</front>
<seriesInfo name="BCP" value="14"/>
<seriesInfo name="RFC" value="2119"/>
<seriesInfo name="DOI" value="10.17487/RFC2119"/>
</reference>
<reference anchor="RFC3986" target="https://www.rfc-editor.org/info/rfc3
986" quoteTitle="true" derivedAnchor="RFC3986">
<front>
<title>Uniform Resource Identifier (URI): Generic Syntax</title>
<author fullname="T. Berners-Lee" initials="T" surname="Berners-Lee"
/>
<author fullname="R. Fielding" initials="R" surname="Fielding"/>
<author fullname="L. Masinter" initials="L" surname="Masinter"/>
<date month="January" year="2005"/>
<abstract>
<t indent="0">A Uniform Resource Identifier (URI) is a compact seq
uence of characters that identifies an abstract or physical resource. This spec
ification defines the generic URI syntax and a process for resolving URI referen
ces that might be in relative form, along with guidelines and security considera
tions for the use of URIs on the Internet. The URI syntax defines a grammar tha
t is a superset of all valid URIs, allowing an implementation to parse the commo
n components of a URI reference without knowing the scheme-specific requirements
of every possible identifier. This specification does not define a generative
grammar for URIs; that task is performed by the individual specifications of eac
h URI scheme. [STANDARDS-TRACK]</t>
</abstract>
</front>
<seriesInfo name="STD" value="66"/>
<seriesInfo name="RFC" value="3986"/>
<seriesInfo name="DOI" value="10.17487/RFC3986"/>
</reference>
<reference anchor="RFC4918" target="https://www.rfc-editor.org/info/rfc4
918" quoteTitle="true" derivedAnchor="RFC4918">
<front>
<title>HTTP Extensions for Web Distributed Authoring and Versioning
(WebDAV)</title>
<author fullname="L. Dusseault" initials="L" role="editor" surname="
Dusseault"/>
<date month="June" year="2007"/>
<abstract>
<t indent="0">Web Distributed Authoring and Versioning (WebDAV) co
nsists of a set of methods, headers, and content-types ancillary to HTTP/1.1 for
the management of resource properties, creation and management of resource coll
ections, URL namespace manipulation, and resource locking (collision avoidance).
</t>
<t indent="0">RFC 2518 was published in February 1999, and this sp
ecification obsoletes RFC 2518 with minor revisions mostly due to interoperabili
ty experience. [STANDARDS-TRACK]</t>
</abstract>
</front>
<seriesInfo name="RFC" value="4918"/>
<seriesInfo name="DOI" value="10.17487/RFC4918"/>
</reference>
<reference anchor="RFC5234" target="https://www.rfc-editor.org/info/rfc5
234" quoteTitle="true" derivedAnchor="RFC5234">
<front>
<title>Augmented BNF for Syntax Specifications: ABNF</title>
<author fullname="D. Crocker" initials="D" role="editor" surname="Cr
ocker"/>
<author fullname="P. Overell" initials="P" surname="Overell"/>
<date month="January" year="2008"/>
<abstract>
<t indent="0">Internet technical specifications often need to defi
ne a formal syntax. Over the years, a modified version of Backus-Naur Form (BNF
), called Augmented BNF (ABNF), has been popular among many Internet specificati
ons. The current specification documents ABNF. It balances compactness and sim
plicity with reasonable representational power. The differences between standar
d BNF and ABNF involve naming rules, repetition, alternatives, order-independenc
e, and value ranges. This specification also supplies additional rule definitio
ns and encoding for a core lexical analyzer of the type common to several Intern
et specifications. [STANDARDS-TRACK]</t>
</abstract>
</front>
<seriesInfo name="STD" value="68"/>
<seriesInfo name="RFC" value="5234"/>
<seriesInfo name="DOI" value="10.17487/RFC5234"/>
</reference>
<reference anchor="RFC5545" target="https://www.rfc-editor.org/info/rfc5
545" quoteTitle="true" derivedAnchor="RFC5545">
<front>
<title>Internet Calendaring and Scheduling Core Object Specification
(iCalendar)</title>
<author fullname="B. Desruisseaux" initials="B" role="editor" surnam
e="Desruisseaux"/>
<date month="September" year="2009"/>
<abstract>
<t indent="0">This document defines the iCalendar data format for
representing and exchanging calendaring and scheduling information such as event
s, to-dos, journal entries, and free/busy information, independent of any partic
ular calendar service or protocol. [STANDARDS-TRACK]</t>
</abstract>
</front>
<seriesInfo name="RFC" value="5545"/>
<seriesInfo name="DOI" value="10.17487/RFC5545"/>
</reference>
<reference anchor="RFC7986" target="https://www.rfc-editor.org/info/rfc7
986" quoteTitle="true" derivedAnchor="RFC7986">
<front>
<title>New Properties for iCalendar</title>
<author fullname="C. Daboo" initials="C" surname="Daboo"/>
<date month="October" year="2016"/>
<abstract>
<t indent="0">This document defines a set of new properties for iC
alendar data and extends the use of some existing properties to the entire iCale
ndar object.</t>
</abstract>
</front>
<seriesInfo name="RFC" value="7986"/>
<seriesInfo name="DOI" value="10.17487/RFC7986"/>
</reference>
<reference anchor="RFC8174" target="https://www.rfc-editor.org/info/rfc8
174" quoteTitle="true" derivedAnchor="RFC8174">
<front>
<title>Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words</ti
tle>
<author fullname="B. Leiba" initials="B" surname="Leiba"/>
<date month="May" year="2017"/>
<abstract>
<t indent="0">RFC 2119 specifies common key words that may be used
in protocol specifications. This document aims to reduce the ambiguity by clar
ifying that only UPPERCASE usage of the key words have the defined special meani
ngs.</t>
</abstract>
</front>
<seriesInfo name="BCP" value="14"/>
<seriesInfo name="RFC" value="8174"/>
<seriesInfo name="DOI" value="10.17487/RFC8174"/>
</reference>
<reference anchor="RFC8288" target="https://www.rfc-editor.org/info/rfc8
288" quoteTitle="true" derivedAnchor="RFC8288">
<front>
<title>Web Linking</title>
<author fullname="M. Nottingham" initials="M" surname="Nottingham"/>
<date month="October" year="2017"/>
<abstract>
<t indent="0">This specification defines a model for the relations
hips between resources on the Web ("links") and the type of those relationships
("link relation types").</t>
<t indent="0">It also defines the serialisation of such links in H
TTP headers with the Link header field.</t>
</abstract>
</front>
<seriesInfo name="RFC" value="8288"/>
<seriesInfo name="DOI" value="10.17487/RFC8288"/>
</reference>
<reference anchor="W3C.REC-skos-reference-20090818" target="https://www.
w3.org/TR/2009/REC-skos-reference-20090818" quoteTitle="true" derivedAnchor="W3C
.REC-skos-reference-20090818">
<front>
<title>SKOS Simple Knowledge Organization System Reference</title>
<author initials="A." surname="Miles" fullname="Alistair Miles">
<organization showOnFrontPage="true"/>
</author>
<author initials="S." surname="Bechhofer" fullname="Sean Bechhofer">
<organization showOnFrontPage="true"/>
</author>
<date month="August" day="18" year="2009"/>
</front>
<seriesInfo name="W3C Recommendation" value="REC-skos-reference-200908
18"/>
</reference>
<reference anchor="W3C.REC-xptr-framework-20030325" target="https://www.
w3.org/TR/2003/REC-xptr-framework-20030325" quoteTitle="true" derivedAnchor="W3C
.REC-xptr-framework-20030325">
<front>
<title>XPointer Framework</title>
<author initials="P." surname="Grosso" fullname="Paul Grosso">
<organization showOnFrontPage="true"/>
</author>
<author initials="E." surname="Maler" fullname="Eve Maler">
<organization showOnFrontPage="true"/>
</author>
<author initials="J." surname="Marsh" fullname="Jonathan Marsh">
<organization showOnFrontPage="true"/>
</author>
<author initials="N." surname="Walsh" fullname="Norman Walsh">
<organization showOnFrontPage="true"/>
</author>
<date month="March" day="25" year="2003"/>
</front>
<seriesInfo name="W3C Recommendation" value="REC-xptr-framework-200303
25"/>
</reference>
<reference anchor="W3C.WD-xptr-xpointer-20021219" target="http://www.w3.
org/TR/2002/WD-xptr-xpointer-20021219" quoteTitle="true" derivedAnchor="W3C.WD-x
ptr-xpointer-20021219">
<front>
<title>XPointer xpointer() Scheme</title>
<author initials="S." surname="DeRose" fullname="Steven DeRose">
<organization showOnFrontPage="true"/>
</author>
<author initials="E." surname="Maler" fullname="Eve Maler">
<organization showOnFrontPage="true"/>
</author>
<author initials="R." surname="Daniel" fullname="Ron Daniel Jr.">
<organization showOnFrontPage="true"/>
</author>
<date month="December" day="19" year="2002"/>
</front>
<seriesInfo name="W3C WD" value="WD-xptr-xpointer-20021219"/>
</reference>
</references>
<references pn="section-12.2">
<name slugifiedName="name-informative-references">Informative References
</name>
<reference anchor="RFC4791" target="https://www.rfc-editor.org/info/rfc4
791" quoteTitle="true" derivedAnchor="RFC4791">
<front>
<title>Calendaring Extensions to WebDAV (CalDAV)</title>
<author fullname="C. Daboo" initials="C" surname="Daboo"/>
<author fullname="B. Desruisseaux" initials="B" surname="Desruisseau
x"/>
<author fullname="L. Dusseault" initials="L" surname="Dusseault"/>
<date month="March" year="2007"/>
<abstract>
<t indent="0">This document defines extensions to the Web Distribu
ted Authoring and Versioning (WebDAV) protocol to specify a standard way of acce
ssing, managing, and sharing calendaring and scheduling information based on the
iCalendar format. This document defines the "calendar-access" feature of CalDA
V. [STANDARDS-TRACK]</t>
</abstract>
</front>
<seriesInfo name="RFC" value="4791"/>
<seriesInfo name="DOI" value="10.17487/RFC4791"/>
</reference>
<reference anchor="RFC8607" target="https://www.rfc-editor.org/info/rfc8
607" quoteTitle="true" derivedAnchor="RFC8607">
<front>
<title>Calendaring Extensions to WebDAV (CalDAV): Managed Attachment
s</title>
<author fullname="C. Daboo" initials="C" surname="Daboo"/>
<author fullname="A. Quillaud" initials="A" surname="Quillaud"/>
<author fullname="K. Murchison" initials="K" role="editor" surname="
Murchison"/>
<date month="June" year="2019"/>
<abstract>
<t indent="0">This specification adds an extension to the Calendar
ing Extensions to WebDAV (CalDAV) to allow attachments associated with iCalendar
data to be stored and managed on the server.</t>
<t indent="0">This specification documents existing code deployed
by multiple vendors. It is published as an Informational specification rather th
an Standards Track due to its noncompliance with multiple best current practices
of HTTP.</t>
</abstract>
</front>
<seriesInfo name="RFC" value="8607"/>
<seriesInfo name="DOI" value="10.17487/RFC8607"/>
</reference>
</references>
</references>
<section numbered="false" removeInRFC="false" toc="include" pn="section-appe
ndix.a">
<name slugifiedName="name-acknowledgements">Acknowledgements</name>
<t indent="0" pn="section-appendix.a-1">
The author would like to thank the members of CalConnect, The author would like to thank the members of CalConnect,
the Calendaring and the Calendaring and
Scheduling Consortium technical committees and the following Scheduling Consortium technical committees, and the following
individuals for contributing their ideas, support and comments: individuals for contributing their ideas, support, and comments:
</t> </t>
<t> <t indent="0" pn="section-appendix.a-2">
Adrian Apthorp, Cyrus Daboo, Marten Gajda, Ken Murchison <contact fullname="Adrian Apthorp"/>, <contact fullname="Cyrus Daboo"/>,
<contact fullname="Marten Gajda"/>, and <contact fullname="Ken Murchison"
/>
</t> </t>
<t> <t indent="0" pn="section-appendix.a-3">
The author would also like to thank CalConnect, the Calendaring and The author would also like to thank CalConnect and the Calendaring and
Scheduling Consortium for advice with this specification. Scheduling Consortium for advice with this specification.
</t> </t>
</section> </section>
</middle> <section anchor="authors-addresses" numbered="false" removeInRFC="false" toc
="include" pn="section-appendix.b">
<!-- *****BACK MATTER ***** --> <name slugifiedName="name-authors-address">Author's Address</name>
<author initials="M." surname="Douglass" fullname="Michael Douglass">
<back> <organization abbrev="Bedework" showOnFrontPage="true">Bedework</organiz
<!-- References split into informative and normative --> ation>
<address>
<!-- There are 2 ways to insert reference entries from the citation librarie <postal>
s: <street>226 3rd Street</street>
1. define an ENTITY at the top, and use "ampersand character"RFC2629; here <city>Troy</city>
(as shown) <region>NY</region>
2. simply use a PI "less than character"?rfc include="reference.RFC.2119.xm <code>12180</code>
l"?> here <country>United States of America</country>
(for I-Ds: include="reference.I-D.narten-iana-considerations-rfc2434bis. </postal>
xml") <email>mdouglass@bedework.com</email>
<uri>https://bedework.com</uri>
Both are cited textually in the same manner: by using xref elements. </address>
If you use the PI option, xml2rfc will, by default, try to find included fi </author>
les in the same </section>
directory as the including file. You can also define the XML_LIBRARY enviro
nment variable
with a value containing a set of directories to search. These can be eithe
r in the local
filing system or remote ones accessed by http (http://domain/dir/... ).-->
<references title="Informative References">
&RFC4791;
&RFC8607;
</references>
<references title="Normative References">
&RFC2119;
&RFC3986;
&RFC4918;
&RFC5234;
&RFC5545;
&RFC7986;
&RFC8174;
&RFC8288;
&W3C.WD-xptr-xpointer-20021219;
&W3C.REC-xptr-framework-20030325;
&W3C.REC-skos-reference-20090818;
</references>
</back> </back>
</rfc> </rfc>
 End of changes. 197 change blocks. 
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