draft-ietf-calext-ical-relations-05.txt   draft-ietf-calext-ical-relations-06.txt 
Network Working Group M. Douglass Network Working Group M. Douglass
Internet-Draft Bedework Internet-Draft Bedework
Updates: 5545 (if approved) July 29, 2020 Updates: 5545 (if approved) December 31, 2020
Intended status: Standards Track Intended status: Standards Track
Expires: January 30, 2021 Expires: July 4, 2021
Support for iCalendar Relationships Support for iCalendar Relationships
draft-ietf-calext-ical-relations-05 draft-ietf-calext-ical-relations-06
Abstract Abstract
This specification updates RELATED-TO defined in [RFC5545] and This specification updates RELATED-TO defined in [RFC5545] and
introduces new iCalendar properties LINK, CONCEPT and REFID to allow introduces new iCalendar properties LINK, CONCEPT and REFID to allow
better linking and grouping of iCalendar components and related data. better linking and grouping of iCalendar components and related data.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 30, 2021. This Internet-Draft will expire on July 4, 2021.
Copyright Notice Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Structured iCalendar relationships . . . . . . . . . . . 3 1.1. Structured iCalendar relationships . . . . . . . . . . . 3
1.2. Grouped iCalendar relationships . . . . . . . . . . . . . 3 1.2. Grouped iCalendar relationships . . . . . . . . . . . . . 3
1.3. Concept relationships . . . . . . . . . . . . . . . . . . 3 1.3. Concept relationships . . . . . . . . . . . . . . . . . . 3
1.4. Linked relationships . . . . . . . . . . . . . . . . . . 4 1.4. Linked relationships . . . . . . . . . . . . . . . . . . 4
1.5. Caching and offline use . . . . . . . . . . . . . . . . . 5 1.5. Caching and offline use . . . . . . . . . . . . . . . . . 5
1.6. Conventions Used in This Document . . . . . . . . . . . . 5 1.6. Conventions Used in This Document . . . . . . . . . . . . 5
2. Reference Types . . . . . . . . . . . . . . . . . . . . . . . 5 2. Reference Types . . . . . . . . . . . . . . . . . . . . . . . 5
3. Link Relation Types . . . . . . . . . . . . . . . . . . . . . 5 3. Link Relation Types . . . . . . . . . . . . . . . . . . . . . 5
4. Redefined Relation Type Value . . . . . . . . . . . . . . . . 5 4. New temporal RELTYPE Parameter values . . . . . . . . . . . . 6
5. New Property Parameters . . . . . . . . . . . . . . . . . . . 8 5. Additional New RELTYPE Parameter Values . . . . . . . . . . . 7
5.1. Rel . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 6. New Property Parameters . . . . . . . . . . . . . . . . . . . 8
5.2. Gap . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 6.1. Link Relation . . . . . . . . . . . . . . . . . . . . . . 8
6. New Value Data Types . . . . . . . . . . . . . . . . . . . . 9 6.2. Gap . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
7. New Properties . . . . . . . . . . . . . . . . . . . . . . . 10 7. New Value Data Types . . . . . . . . . . . . . . . . . . . . 9
7.1. Concept . . . . . . . . . . . . . . . . . . . . . . . . . 10 8. New Properties . . . . . . . . . . . . . . . . . . . . . . . 9
7.2. Link . . . . . . . . . . . . . . . . . . . . . . . . . . 11 8.1. Concept . . . . . . . . . . . . . . . . . . . . . . . . . 9
7.3. Refid . . . . . . . . . . . . . . . . . . . . . . . . . . 13 8.2. Link . . . . . . . . . . . . . . . . . . . . . . . . . . 10
8. Redefined RELATED-TO Property . . . . . . . . . . . . . . . . 13 8.3. Refid . . . . . . . . . . . . . . . . . . . . . . . . . . 11
8.1. RELATED-TO . . . . . . . . . . . . . . . . . . . . . . . 14 9. Redefined RELATED-TO Property . . . . . . . . . . . . . . . . 12
9. Security Considerations . . . . . . . . . . . . . . . . . . . 16 9.1. RELATED-TO . . . . . . . . . . . . . . . . . . . . . . . 12
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 10. Security Considerations . . . . . . . . . . . . . . . . . . . 14
10.1. iCalendar Property Registrations . . . . . . . . . . . . 16 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
10.2. iCalendar Property Parameter Registrations . . . . . . . 16 11.1. iCalendar Property Registrations . . . . . . . . . . . . 14
10.3. iCalendar Value Data Type Registrations . . . . . . . . 16 11.2. iCalendar Property Parameter Registrations . . . . . . . 15
10.4. iCalendar RELTYPE Value Registrations . . . . . . . . . 17 11.3. iCalendar Value Data Type Registrations . . . . . . . . 15
10.5. New Reference Type Registration . . . . . . . . . . . . 17 11.4. iCalendar RELTYPE Value Registrations . . . . . . . . . 15
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 17 11.5. New Reference Type Registration . . . . . . . . . . . . 16
12. Normative References . . . . . . . . . . . . . . . . . . . . 18 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 16
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 19 13. Normative References . . . . . . . . . . . . . . . . . . . . 16
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 17
1. Introduction 1. Introduction
iCalendar entities often need to be related to each other or to iCalendar entities often need to be related to each other or to
associated meta-data. These relationships can take the following associated meta-data. The specifications below support relationships
forms of the following forms:
Structured iCalendar: iCalendar entities are related to each other Structured iCalendar: iCalendar entities can be related to each
in some structured way, for example as parent, sibling, before, other in some structured way, for example as parent, sibling,
after. before, after.
Grouped iCalendar: iCalendar entities are related to each other as a Grouped iCalendar: iCalendar entities can be related to each other
group. CATEGORIES are often used for this purpose but are as a group. CATEGORIES are often used for this purpose but are
problematic for application developers. problematic for application developers due to their lack of
consistency and use as a free-form tag.
Linked: Entities are linked to each other through typed references. Linked: Entities can be linked to other entities such as vcards
through a URI and associated REL and FMTTYPE parameters.
1.1. Structured iCalendar relationships 1.1. Structured iCalendar relationships
The currently existing iCalendar [RFC5545] RELATED-TO property has no The currently existing iCalendar [RFC5545] RELATED-TO property has no
support for temporal relationships as used by standard project support for temporal relationships as used by standard project
management tools. management tools.
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. These and lag values, and RELATED-TO is extended to allow URI values.
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.
1.2. Grouped iCalendar relationships 1.2. Grouped iCalendar relationships
This specification defines a new REFID property which allows This specification defines a new REFID property which allows
arbitrary groups of entities to be associated with the same key arbitrary groups of entities to be associated with the same key
value. value.
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 related to the same object and retrieval of a components that are related to the same object and retrieval of a
component based on this key. This may be, for example, to identify component based on this key. Two examples of how this may be used
the tasks associated with a given project without having to are to identify the tasks associated with a given project without
communicate the task structure of the project, or, for example, in a having to communicate the task structure of the project, and to group
package delivery system all tasks associated to a specific package. all tasks associated to a specific package in a package delivery
system.
As such, the presence of a REFID property imparts no meaning to the As such, the presence of a REFID property imparts no meaning to the
component. It is merely a key to allow retrieval. This is distinct component. It is merely a key to allow retrieval. This is distinct
from categorisation which, while allowing grouping also adds meaning from categorisation which, while allowing grouping also adds meaning
to the component to which it is attached. to the component to which it is attached.
1.3. Concept relationships 1.3. Concept relationships
The name CONCEPT is used by the Simple Knowledge Organization System The name CONCEPT is used by the Simple Knowledge Organization System
defined in [W3C.CR-skos-reference-20090317]. This more accurately defined in [W3C.CR-skos-reference-20090317]. The term "concept" more
defines what we mean by a category. It's not the words but the accurately defines what we often mean by a category. It's not the
meaning. text string that is important but the meaning attached to it. For
example, the term "football" can mean very different sports.
The introduction of CONCEPT allows a more structured approach to The introduction of CONCEPT allows a more structured approach to
categorization, with the possibility of namespaced and path-like categorization, with the possibility of namespaced and path-like
values. Unlike REFID the CONCEPT property imparts some meaning. It values. Unlike REFID the CONCEPT property imparts some meaning. It
is assumed that the value of this property will reference a well is assumed that the value of this property will reference a well
defined category. defined category.
The current [RFC5545] CATEGORY property is used as a free form The current [RFC5545] CATEGORY property is used as a free form
'tagging' field. As such it is difficult to establish formal 'tagging' field. As such it is difficult to establish formal
relationships between components based on their category. relationships between components based on their category.
Rather than attempt to add semantics to the current property it Rather than attempt to add semantics to the CATEGORY property it
seeems best to continue its usage as an informal tag and establish a seems best to continue its usage as an informal tag and establish a
new property with more constraints. new CONCEPT property with more constraints.
1.4. Linked relationships 1.4. Linked relationships
The currently existing iCalendar standard [RFC5545] lacks a general The currently existing iCalendar standard [RFC5545] lacks a general
purpose method for referencing additional, external information purpose method for referencing additional, external information
relating to calendar components. relating to calendar components.
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 information that can provide additional information about an
iCalendar component. This new LINK property is closely aligned to iCalendar component. This new LINK property is closely aligned to
the LINK header defined in [RFC5988] the LINK header defined in [RFC8288]
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 meta-data or related resources. By providing type and format
information as parameters, clients and servers are able to discover information as parameters, clients and servers are able to discover
interesting references and make use of them, perhaps for indexing or interesting references and make use of them, perhaps for indexing or
the presentation of interesting links for the user. the presentation of interesting links for the user.
It is often necessary to relate calendar components. The current It is also often necessary to reference calendar components in other
RELATED-TO property only allows for a UID which is inadequate for collections. For example, a VEVENT might refer to a VTODO from which
many purposes. Allowing other value types for that property may help it was derived. The PARENT, SIBLING and CHILD relationships defined
but might raise a number of backward compatibility issues. The link for the RELATED-TO property only allow for a UID which is inadequate
property can link components in different collections or even on for many purposes. Allowing other value types for those
different servers. relationships may help but would cause backward compatibility issues.
The link property can link components in different collections or
even on different servers.
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 source of that information. The actual event may have been consumed
from a feed or an ics file on a web site. A LINK property can from a feed or an ics file on a web site. A LINK property can
provide a reference to the originator of the event. provide a reference to the originator of the event.
Beyond the need to relate elements temporally, project management Beyond the need to relate elements temporally, project management
tools often need to be able to specify the relationships between the tools often need to be able to specify the relationships between the
various events and tasks which make up a project. The LINK property various events and tasks which make up a project. The LINK property
provides such a mechanism. provides such a mechanism.
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To facilitate offline display the link type may identify important To facilitate offline display the link type may identify important
pieces of data which should be downloaded in advance. pieces of data which should be downloaded in advance.
In general, the calendar entity should be self explanatory without In general, the calendar entity should be self explanatory without
the need to download referenced meta-data such as a web page. the need to download referenced meta-data such as a web page.
1.6. Conventions Used in This Document 1.6. Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY" and
"OPTIONAL" in this document are to be interpreted as described in "OPTIONAL" in this document are to be interpreted as described in BCP
[RFC2119]. 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. Reference Types 2. Reference Types
The actual reference value can take three forms specified by the type The actual reference value can take three forms specified by the type
parameter parameter
URI: The default type. This is a URI referring to the target. URI: The default type. This is a URI referring to the target.
UID: This allows for linking within a single collection and the UID: This allows for linking within a single collection and the
value is assumed to be another component within that collection. value MUST be another component within that collection.
REFERENCE: An xpointer. In an XML environment it may be necessary REFERENCE: An XPointer. In an XML environment it may be necessary
to refer to an external XML artifact. The XPointer is defined in to refer to an external XML artifact. The XPointer is defined in
[W3C.WD-xptr-xpointer-20021219] and allows addressing portions of [W3C.WD-xptr-xpointer-20021219] and allows addressing portions of
XML documents. XML documents.
3. Link Relation Types 3. Link Relation Types
[RFC5988] defines two forms of relation type, registered and [RFC8288] defines two forms of relation type: registered and
extension. Registered relation types are added to a registry defined extension. Registered relation types are added to the Link Relations
by [RFC5988] while extension relation types are specified as unique registry as specified in Section 2.1.1 of [RFC8288]. Extension
unregistered URIs, (at least unregistered in the [RFC5988] registry). relation types, defined in Section 2.1.2 of [RFC8288], are specified
as unique URIs that are not registered in the registry.
The relation types defined here will be registered with IANA in
accordance with the specifications in [RFC5988].
4. Redefined Relation Type Value
Relationship parameter type values are defined in section 3.2.15. of
[RFC5545]. This specification redefines that type to include the new
temporal relationship values FINISHTOSTART, FINISHTOFINISH,
STARTTOFINISH and STARTTOSTART. It also adds the DEPENDS-ON value to
provide a link to a component upon which the current component
depends.
Format Definition:
This property parameter is defined by the following notation:
reltypeparam = "RELTYPE" "="
("PARENT" ; Parent relationship - Default
/ "CHILD" ; Child relationship
/ "SIBLING" ; Sibling relationship
/ "DEPENDS-ON" ; refers to previous component
/ "REFID" ; Relationship based on REFID
/ "CONCEPT"
; Relationship based on CONCEPT
/ "FINISHTOSTART" ; Temporal relationship
/ "FINISHTOFINISH" ; Temporal relationship
/ "STARTTOFINISH" ; Temporal relationship
/ "STARTTOSTART" ; Temporal relationship
/ iana-token ; Some other IANA-registered
; iCalendar relationship type
/ x-name) ; A non-standard, experimental
; relationship type
Description: This parameter can be specified on a property that
references another related calendar component. The parameter may
specify the hierarchical relationship type of the calendar
component referenced by the property when the value is PARENT,
CHILD or SIBLING. If this parameter is not specified on an
allowable property, the default relationship type is PARENT.
Applications MUST treat x-name and iana-token values they don't
recognize the same way as they would the PARENT value.
This parameter defines the temporal relationship when the value is
one of the project management standard relationships
FINISHTOSTART, FINISHTOFINISH, STARTTOFINISH or STARTTOSTART.
This property will be present in the predecessor entity and will
refer to the successor entity. The GAP parameter specifies the
lead or lag time between the predecessor and the successor. In
the description of each temporal relationship below we refer to
Task-A which contains and controls the relationship and Task-B the
target of the relationship.
RELTYPE=PARENT: See [RFC5545] section 3.2.15.
RELTYPE=CHILD: See [RFC5545] section 3.2.15. The relation types defined in Section 6.1 will be registered with
IANA in accordance with the specifications in [RFC8288].
RELTYPE=SIBLING: See [RFC5545] section 3.2.15. 4. New temporal RELTYPE Parameter values
RELTYPE=DEPENDS-ON: Indicates that the current calendar component This section defines the usual temporal relationships for use with
depends on the referenced calendar component in some manner. For the RELTYPE parameter redefined in Section 3.2.15 of [RFC5545]:
example a task may be blocked waiting on the other, referenced, FINISHTOSTART, FINISHTOFINISH, STARTTOFINISH or STARTTOSTART.
task.
RELTYPE=REFID: Establishes a reference from the current component to The [RFC5545] RELATED-TO property with one or more of these temporal
components with a REFID property which matches the value given in relationships will be present in the predecessor entity and will
the associated RELATED-TO property. refer to the successor entity.
RELTYPE=CONCEPT: Establishes a reference from the current component The GAP parameter (see Section 6.2) specifies the lead or lag time
to components with a CONCEPT property which matches the value between the predecessor and the successor. In the description of
given in the associated RELATED-TO property. each temporal relationship below we refer to Task-A, which contains
and controls the relationship, and Task-B the target of the
relationship.
RELTYPE=FINISHTOSTART: Task-B cannot start until Task-A finishes. RELTYPE=FINISHTOSTART: Task-B cannot start until Task-A finishes.
For example, when sanding is complete, painting can begin. For example, when sanding is complete, painting can begin.
============ ============
| Task-A |--+ | Task-A |--+
============ | ============ |
| |
V V
============ ============
skipping to change at page 8, line 28 skipping to change at page 7, line 32
============ ============
+--| Task-A | +--| Task-A |
| ============ | ============
| |
| ============ | ============
+->| Task-B | +->| Task-B |
============ ============
Figure 4: Start to start relationship Figure 4: Start to start relationship
5. New Property Parameters 5. Additional New RELTYPE Parameter Values
5.1. Rel This section defines the additional relationships below:
Parameter name: REL RELTYPE=DEPENDS-ON: Indicates that the current calendar component
depends on the referenced calendar component in some manner. For
example a task may be blocked waiting on the other, referenced,
task.
RELTYPE=REFID: Establishes a reference from the current component to
components with a REFID property which matches the value given in
the associated RELATED-TO property.
RELTYPE=CONCEPT: Establishes a reference from the current component
to components with a CONCEPT property which matches the value
given in the associated RELATED-TO property.
6. New Property Parameters
6.1. Link Relation
Parameter name: LINKREL
Purpose: To specify the relationship of data referenced by a LINK Purpose: To specify the relationship of data referenced by a LINK
property. property.
Format Definition: Format Definition:
This parameter is defined by the following notation: This parameter is defined by the following notation:
relparam = "REL" "=" linkrelparam = "REL" "="
("SOURCE" ; Link to source of this component ("SOURCE" ; Link to source of this component
/ DQUOTE uri DQUOTE / DQUOTE uri DQUOTE
/ x-name ; Experimental reference type
/ iana-token) ; Other IANA registered type / iana-token) ; Other IANA registered type
Description: This parameter MUST be specified on all LINK Description: This parameter MUST be specified on all LINK
properties, and defines the type of reference. This allows properties, and defines the type of reference. This allows
programs consuming this data to automatically scan for references programs consuming this data to automatically scan for references
they support. In addition to the values defined here any value they support. In addition to the values defined here any value
defined in [RFC5988] may be used. There is no default relation defined in [RFC8288] may be used. There is no default relation
type. type.
REL=SOURCE: identifies the source of the event information. REL=SOURCE: identifies the source of the event information.
Registration: These relation types are registered in [RFC5988] Registration: These relation types are registered in [RFC8288]
5.2. Gap 6.2. Gap
Parameter name: GAP Parameter name: GAP
Purpose: To specify the length of the gap, positive or negative Purpose: To specify the length of the gap, positive or negative,
between two temporaly related components. between two temporaly related components.
Format Definition: Format Definition:
This parameter is defined by the following notation: This parameter is defined by the following notation:
gapparam = "GAP" "=" dur-value gapparam = "GAP" "=" dur-value
Description: This parameter MAY be specified on the RELATED-TO Description: This parameter MAY be specified on the RELATED-TO
property, and defines the duration of time between the predecessor property, and defines the duration of time between the predecessor
skipping to change at page 9, line 39 skipping to change at page 9, line 14
An example of lag time might be if task A is "paint the room" and An example of lag time might be if task A is "paint the room" and
task B is "hang the drapes" then task A may be related to task B task B is "hang the drapes" then task A may be related to task B
with RELTYPE=FINISHTOSTART with a gap long enough for the paint to with RELTYPE=FINISHTOSTART with a gap long enough for the paint to
dry. dry.
An example of lead time might be to relate a 1 week task A to the An example of lead time might be to relate a 1 week task A to the
end of task B with RELTYPE=STARTTOFINISH and a negative gap of 1 end of task B with RELTYPE=STARTTOFINISH and a negative gap of 1
week so they finish at the same time. week so they finish at the same time.
6. New Value Data Types 7. New Value Data Types
This specification defines the following new value types to be used This specification defines the following new value types to be used
with the VALUE property parameter: with the VALUE property parameter:
UID VALUE=UID indicates that the associated value is the UID for a UID VALUE=UID indicates that the associated value is the UID for a
component. component.
REFERENCE VALUE=REFERENCE indicates that the associated value is an REFERENCE VALUE=REFERENCE indicates that the associated value is an
xpointer referencing an associated XML artifact. XPointer referencing an associated XML artifact.
7. New Properties 8. New Properties
7.1. Concept 8.1. Concept
Property name: CONCEPT Property name: CONCEPT
Purpose: This property defines the formal categories for a calendar Purpose: This property defines the formal categories for a calendar
component. component.
Value type: URI Value type: URI
Property Parameters: IANA, and non-standard parameters can be Property Parameters: IANA, and non-standard parameters can be
specified on this property. specified on this property.
skipping to change at page 10, line 41 skipping to change at page 10, line 12
This categorization is distinct from the more informal "tagging" This categorization is distinct from the more informal "tagging"
of components provided by the existing CATEGORIES property. It is of components provided by the existing CATEGORIES property. It is
expected that the value of the CONCEPT property will reference an expected that the value of the CONCEPT property will reference an
external resource which provides information about the external resource which provides information about the
categorization. categorization.
In addition, a structured URI value allows for hierarchical In addition, a structured URI value allows for hierarchical
categorization of events. categorization of events.
Possible category resources are the various proprietary systems, Possible category resources are the various proprietary systems,
for example Library of Congress, or an open source derived from for example Library of Congress, or an open source of
something like the dmoz.org data. categorisation data.
Format Definition: Format Definition:
This property is defined by the following notation: This property is defined by the following notation:
concept = "CONCEPT" conceptparam ":" concept = "CONCEPT" conceptparam ":"
uri CRLF uri CRLF
conceptparam = *( conceptparam = *(";" other-param)
;
; The following is OPTIONAL,
; and MAY occur more than once.
;
(";" other-param)
;
)
Example: Example:
The following is an example of this property. It points to a server The following is an example of this property. It points to a server
acting as the source for the calendar object. acting as the source for the calendar object.
SCONCEPT:http://example.com/event-types/sports
CONCEPT:http://example.com/event-types/arts/music CONCEPT:http://example.com/event-types/arts/music
CONCEPT:http://example.com/task-types/delivery
7.2. Link 8.2. Link
Property name: LINK Property name: LINK
Purpose: This property provides a reference to external information Purpose: This property provides a reference to external information
about a component. about a component.
Value type: URI, TEXT or REFERENCE Value type: URI, TEXT or REFERENCE
Property Parameters: Non-standard, reference type or format type Property Parameters: The VALUE parameter is required. Non-standard,
parameters can be specified on this property. reference type or format type parameters can also be specified on
this property. The LABEL parameter is defined in [RFC7986]
Conformance: This property MAY be specified in any iCalendar Conformance: This property MAY be specified in any iCalendar
component. component.
Description: When used in a component the value of this property Description: When used in a component the value of this property
points to additional information related to the component. For points to additional information related to the component. For
example, it may reference the originating web server. example, it may reference the originating web server.
Format Definition: Format Definition:
This property is defined by the following notation: This property is defined by the following notation:
link = "LINK" linkparam / link = "LINK" linkparam ":"
( ( text / ; for VALUE=REFERENCE
";" "VALUE" "=" "TEXT" uri / ; for VALUE=URI
":" text text ) ; for VALUE=TEXT
)
(
";" "VALUE" "=" "REFERENCE"
":" text
)
(
";" "VALUE" "=" "URI"
":" uri
)
CRLF CRLF
linkparam = *( linkparam = ; the elements herein may appear in any order,
; and the order is not significant.
; the following is MANDATORY
; and MAY occur more than once
(";" relparam) /
; the following are MANDATORY
; but MUST NOT occur more than once
(";" fmttypeparam) / (";" "VALUE" "=" ("UID" /
(";" labelparam) / "URI" /
; labelparam is defined in ... "TEXT"))
1*(";" linkrelparam)
(";" fmttypeparam)
(";" labelparam)
*(";" other-param)
; the following is OPTIONAL Example:
; and MAY occur more than once
(";" xparam) The following is an example of this property which provides a
reference to the source for the calendar object.
) LINK;LINKREL=SOURCE;LABEL=Venue;VALUE=URI:http://example.com/events
Example: Example:
The following is an example of this property. It points to a server The following is an example of this property which provides a
acting as the source for the calendar object. reference to an entity from which this one was derived. The link
relation is a vendor defined value
LINK;REL=SOURCE;LABEL=The Egg:http://example.com/events LINK;LINKREL="https://example.com/linkrel/derivedFrom";VALUE=URI:
http://example.com/tasks/01234567-abcd1234.ics
7.3. Refid 8.3. Refid
Property name: REFID Property name: REFID
Purpose: This property value acts as a key for associated iCalendar Purpose: This property value acts as a key for associated iCalendar
entities. entities.
Value type: TEXT Value type: TEXT
Property Parameters: Non-standard parameters can be specified on Property Parameters: Non-standard parameters can be specified on
this property. this property.
Conformance: This property MAY be specified multiple times in any Conformance: This property MAY be specified multiple times in any
iCalendar component. iCalendar component.
Description: The value of this property is a text identifier that Description: The value of this property is free-form text that
allows associated components to be located or retrieved as a creates an identifier for associated components. All components
whole. For example all of the events in a travel itinerary would that use the same REFID value are associated through that value
have the same REFID value. 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,
so as to be grouped together.
Format Definition: Format Definition:
This property is defined by the following notation: This property is defined by the following notation:
refid = "REFID" refidparam ":" text CRLF refid = "REFID" refidparam ":" text CRLF
refidparam = *( refidparam = *(";" other-param)
; the following is OPTIONAL
; and MAY occur more than once
(";" xparam)
)
Example: Example:
The following is an example of this property. The following is an example of this property.
REFID:itinerary-2014-11-17 REFID:itinerary-2014-11-17
8. Redefined RELATED-TO Property 9. Redefined RELATED-TO Property
8.1. RELATED-TO
9.1. RELATED-TO
Property name: RELATED-TO Property name: RELATED-TO
Purpose: This property is used to represent a relationship or Purpose: This property is used to represent a relationship or
reference between one calendar component and another. The reference between one calendar component and another. The
definition here extends the definition in Section 3.8.4.5. of definition here extends the definition in Section 3.8.4.5 of
[RFC5545] by allowing URI or UID values and a GAP parameter. [RFC5545] by allowing URI or UID values and a GAP parameter.
Value type: URI, UID or TEXT Value type: URI, UID or TEXT
Property Parameters: Relationship type, IANA and non-standard Property Parameters: Relationship type, IANA and non-standard
property parameters can be specified on this property. property parameters can be specified on this property.
Conformance: This property MAY be specified in any iCalendar Conformance: This property MAY be specified in any iCalendar
component. component.
skipping to change at page 14, line 41 skipping to change at page 13, line 25
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.
The PARENT relationship indicates that the calendar component is a The PARENT relationship indicates that the calendar component is a
subordinate of the referenced calendar component. The CHILD subordinate of the referenced calendar component. The CHILD
relationship indicates that the calendar component is a superior relationship indicates that the calendar component is a superior
of the referenced calendar component. The SIBLING relationship of the referenced calendar component. The SIBLING relationship
indicates that the calendar component is a peer of the referenced indicates that the calendar component is a peer of the referenced
calendar component. calendar component.
To preserve backwards compatibility the value type MUST be UID
when the PARENT, SIBLING or CHILD relationships are specified.
The FINISHTOSTART, FINISHTOFINISH, STARTTOFINISH or STARTTOSTART The FINISHTOSTART, FINISHTOFINISH, STARTTOFINISH or STARTTOSTART
relationships define temporal relationships as specified in the relationships define temporal relationships as specified in the
reltype parameter definition. reltype parameter definition.
Changes to a calendar component referenced by this property can 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 changed in a corresponding way. Similarly, if a
PARENT calendar component is cancelled or deleted, then there is PARENT calendar component is cancelled 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. It is up to the target relationship of calendar components. It is up to the target
calendar system to maintain any property implications of this calendar system to maintain any property implications of this
relationship. relationship.
Format Definition: Format Definition:
This property is defined by the following notation: This property is defined by the following notation:
related = "RELATED-TO" relparam ( ":" text ) / related = "RELATED-TO" relparam ":"
( ( uid / ; for VALUE=UID
";" "VALUE" "=" "UID" uri / ; for VALUE=URI
":" uid text ) ; for VALUE=TEXT or default
) CRLF
(
";" "VALUE" "=" "URI"
":" uri
)
CRLF
relparam = *( relparam = ; the elements herein may appear in any order,
; ; and the order is not significant.
; The following are OPTIONAL, [";" "VALUE" "=" ("UID" /
; but MUST NOT occur more than once. "URI" /
; "TEXT")]
(";" reltypeparam) / [";" reltypeparam]
(";" gapparam) / [";" gapparam]
; *(";" other-param)
; The following is OPTIONAL,
; and MAY occur more than once.
;
(";" other-param)
;
)
Example: Example:
The following are examples of this property. The following are examples of this property.
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:
http://example.com/caldav/user/jb/cal/ http://example.com/caldav/user/jb/cal/
19960401-080045-4000F192713.ics 19960401-080045-4000F192713.ics
9. Security Considerations 10. Security Considerations
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 [RFC3986] for a entailed in using the URIs provided as values. See [RFC3986] for a
discussion of the security considerations relating to URIs. discussion of the security considerations relating to URIs.
The CONCEPT and redefined RELATED-TO property have the same issues in The CONCEPT and redefined RELATED-TO property have the same issues in
that values may be URIs. that values may be URIs.
10. IANA Considerations 11. IANA Considerations
10.1. iCalendar Property Registrations 11.1. iCalendar Property Registrations
The following iCalendar property names have been added to the The following iCalendar property names have been added to the
iCalendar Properties Registry defined in Section 8.3.2 of [RFC5545] iCalendar Properties Registry defined in Section 8.3.2 of [RFC5545]
+----------+---------+-------------+ +----------+---------+-------------+
| Property | Status | Reference | | Property | Status | Reference |
+----------+---------+-------------+ +----------+---------+-------------+
| CONCEPT | Current | Section 7.1 | | CONCEPT | Current | Section 8.1 |
| LINK | Current | Section 7.2 | | LINK | Current | Section 8.2 |
| REFID | Current | Section 7.3 | | REFID | Current | Section 8.3 |
+----------+---------+-------------+ +----------+---------+-------------+
10.2. iCalendar Property Parameter Registrations 11.2. iCalendar Property Parameter Registrations
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 Section 8.3.3 of
[RFC5545] [RFC5545]
+-----------+---------+-------------+ +-----------+---------+-------------+
| Parameter | Status | Reference | | Parameter | Status | Reference |
+-----------+---------+-------------+ +-----------+---------+-------------+
| REL | Current | Section 5.1 | | REL | Current | Section 6.1 |
| GAP | Current | Section 5.2 | | GAP | Current | Section 6.2 |
+-----------+---------+-------------+ +-----------+---------+-------------+
10.3. iCalendar Value Data Type Registrations 11.3. iCalendar Value Data Type Registrations
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 Section 8.3.4 of
[RFC5545] [RFC5545]
+-----------------+---------+-----------+ +-----------------+---------+-----------+
| Value Data Type | Status | Reference | | Value Data Type | Status | Reference |
+-----------------+---------+-----------+ +-----------------+---------+-----------+
| UID | Current | Section 6 | | UID | Current | Section 7 |
| REFERENCE | Current | Section 6 | | REFERENCE | Current | Section 7 |
+-----------------+---------+-----------+ +-----------------+---------+-----------+
10.4. iCalendar RELTYPE Value Registrations 11.4. iCalendar RELTYPE Value Registrations
The following iCalendar "RELTYPE" values have been added to the The following iCalendar "RELTYPE" values have been added to the
iCalendar Relationship Types Registry defined in Section 8.3.8 of iCalendar Relationship Types Registry defined in Section 8.3.8 of
[RFC5545] [RFC5545]
+-------------------+---------+-----------+ +-------------------+---------+-----------+
| Relationship Type | Status | Reference | | Relationship Type | Status | Reference |
+-------------------+---------+-----------+ +-------------------+---------+-----------+
| DEPENDS-ON | Current | Section 4 | | DEPENDS-ON | Current | Section 5 |
| REFID | Current | Section 4 | | REFID | Current | Section 5 |
| CONCEPT | Current | Section 4 | | CONCEPT | Current | Section 5 |
| FINISHTOSTART | Current | Section 4 | | FINISHTOSTART | Current | Section 4 |
| FINISHTOFINISH | Current | Section 4 | | FINISHTOFINISH | Current | Section 4 |
| STARTTOFINISH | Current | Section 4 | | STARTTOFINISH | Current | Section 4 |
| STARTTOSTART | Current | Section 4 | | STARTTOSTART | Current | Section 4 |
+-------------------+---------+-----------+ +-------------------+---------+-----------+
10.5. New Reference Type Registration 11.5. New Reference Type Registration
The following link relation values have been added to the Reference The following link relation values have been added to the Reference
Types Registry defined in Section 6.2.2 of [RFC5988] Types Registry defined in Section 6.2.2 of [RFC8288]
+--------+---------+-------------+ +--------+---------+-------------+
| Name | Status | Reference | | Name | Status | Reference |
+--------+---------+-------------+ +--------+---------+-------------+
| SOURCE | Current | Section 5.1 | | SOURCE | Current | Section 6.1 |
+--------+---------+-------------+ +--------+---------+-------------+
11. Acknowledgements 12. Acknowledgements
The author would like to thank the members of the Calendaring and The author would like to thank the members of 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:
Adrian Apthorp, Cyrus Daboo, Marten Gajda, Ken Murchison Adrian Apthorp, Cyrus Daboo, Marten Gajda, Ken Murchison
The author would also like to thank CalConnect, the Calendaring and The author would also like to thank CalConnect, the Calendaring and
Scheduling Consortium for advice with this specification. Scheduling Consortium for advice with this specification.
12. Normative References 13. Normative References
[I-D.daboo-caldav-attachments] [I-D.daboo-caldav-attachments]
Daboo, C. and A. Quillaud, "CalDAV Managed Attachments", Daboo, C. and A. Quillaud, "CalDAV Managed Attachments",
draft-daboo-caldav-attachments-03 (work in progress), draft-daboo-caldav-attachments-03 (work in progress),
February 2014. February 2014.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/info/rfc3986>.
[RFC5545] Desruisseaux, B., Ed., "Internet Calendaring and [RFC5545] Desruisseaux, B., Ed., "Internet Calendaring and
Scheduling Core Object Specification (iCalendar)", Scheduling Core Object Specification (iCalendar)",
RFC 5545, DOI 10.17487/RFC5545, September 2009, RFC 5545, DOI 10.17487/RFC5545, September 2009,
<https://www.rfc-editor.org/info/rfc5545>. <https://www.rfc-editor.org/info/rfc5545>.
[RFC5988] Nottingham, M., "Web Linking", RFC 5988, [RFC7986] Daboo, C., "New Properties for iCalendar", RFC 7986,
DOI 10.17487/RFC5988, October 2010, DOI 10.17487/RFC7986, October 2016,
<https://www.rfc-editor.org/info/rfc5988>. <https://www.rfc-editor.org/info/rfc7986>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8288] Nottingham, M., "Web Linking", RFC 8288,
DOI 10.17487/RFC8288, October 2017,
<https://www.rfc-editor.org/info/rfc8288>.
[W3C.CR-skos-reference-20090317] [W3C.CR-skos-reference-20090317]
Bechhofer, S. and A. Miles, "SKOS Simple Knowledge Bechhofer, S. and A. Miles, "SKOS Simple Knowledge
Organization System Reference", World Wide Web Consortium Organization System Reference", World Wide Web Consortium
CR CR-skos-reference-20090317, March 2009, CR CR-skos-reference-20090317, March 2009,
<http://www.w3.org/TR/2009/CR-skos-reference-20090317>. <http://www.w3.org/TR/2009/CR-skos-reference-20090317>.
[W3C.REC-xml-20060816]
Bray, T., Paoli, J., Sperberg-McQueen, M., Maler, E., and
F. Yergeau, "Extensible Markup Language (XML) 1.0 (Fourth
Edition)", World Wide Web Consortium Recommendation REC-
xml-20060816, August 2006,
<http://www.w3.org/TR/2006/REC-xml-20060816>.
[W3C.WD-xptr-xpointer-20021219] [W3C.WD-xptr-xpointer-20021219]
DeRose, S., Daniel, R., and E. Maler, "XPointer xpointer() DeRose, S., Daniel, R., and E. Maler, "XPointer xpointer()
Scheme", World Wide Web Consortium WD WD-xptr-xpointer- Scheme", World Wide Web Consortium WD WD-xptr-xpointer-
20021219, December 2002, 20021219, December 2002,
<http://www.w3.org/TR/2002/WD-xptr-xpointer-20021219>. <http://www.w3.org/TR/2002/WD-xptr-xpointer-20021219>.
Author's Address Author's Address
Michael Douglass Michael Douglass
Bedework Bedework
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