Network Working Group M. Douglass
Internet-Draft RPI
Intended status: Standards Track C. Daboo
Expires: January 6, 2011 Apple
July 5, 2010
Timezone XML Specification
draft-douglass-timezone-xml-00
Abstract
This specification describes a format for describing timezone
information for software and services.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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document authors. All rights reserved.
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to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Schema Definition . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Common Requirements . . . . . . . . . . . . . . . . . . . 5
3.2. TZ:TimeZone XML element . . . . . . . . . . . . . . . . . 5
3.2.1. TZ:Name XML element within TZ:TimeZone . . . . . . . . 5
3.2.2. TZ:Description XML element within TZ:TimeZone . . . . 6
3.2.3. TZ:InfoURL XML element within TZ:TimeZone . . . . . . 6
3.2.4. TZ:CalendarScale XML element within TZ:TimeZone . . . 6
3.2.5. TZ:ReferencedControllingAuthority XML element
within TZ:TimeZone . . . . . . . . . . . . . . . . . . 6
3.2.6. TZ:StandardTime XML element within TZ:TimeZone . . . . 7
3.2.6.1. TZ:Name XML element within TZ:StandardTime . . . . 7
3.2.6.2. TZ:BaseUtcOffset XML element within
TZ:StandardTime . . . . . . . . . . . . . . . . . 7
3.2.6.2.1. TZ:BaseUtcOffsetValue XML element within
TZ:BaseUtcOffset . . . . . . . . . . . . . . . 7
3.2.7. TZ:StandardTimeChange XML element within
TZ:TimeZone . . . . . . . . . . . . . . . . . . . . . 7
3.2.7.1. TZ:Name XML element within
TZ:StandardTimeChange . . . . . . . . . . . . . . 8
3.2.7.2. TZ:OffsetChange XML element within
TZ:StandardTimeChange . . . . . . . . . . . . . . 8
3.3. TZ:EffectiveYearRange XML element . . . . . . . . . . . . 8
3.3.1. TZ:TransitionPeriod XML element within
TZ:EffectiveYearRange . . . . . . . . . . . . . . . . 9
3.3.1.1. TZ:Start and TZ:End XML elements within
TZ:TransitionPeriod . . . . . . . . . . . . . . . 9
3.3.1.1.1. TZ:Month XML element within TZ:Start or
TZ:End . . . . . . . . . . . . . . . . . . . . 9
3.3.1.1.2. TZ:DayOfMonth XML element within TZ:Start
or TZ:End . . . . . . . . . . . . . . . . . . 10
3.3.1.1.3. TZ:DayOfWeek XML element within TZ:Start
or TZ:End . . . . . . . . . . . . . . . . . . 10
3.3.1.1.4. TZ:TimeOfDay XML element within TZ:Start
or TZ:End . . . . . . . . . . . . . . . . . . 11
3.4. TZ:ControllingAuthority XML element . . . . . . . . . . . 11
4. Example TZ XML . . . . . . . . . . . . . . . . . . . . . . . . 12
5. Security Considerations . . . . . . . . . . . . . . . . . . . 13
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
6.1. Namespace Registration . . . . . . . . . . . . . . . . . . 13
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6.2. Media Type . . . . . . . . . . . . . . . . . . . . . . . . 14
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15
8. Appendix A: RelaxNG Schemas for TZ XML . . . . . . . . . . . . 15
8.1. TimeZone . . . . . . . . . . . . . . . . . . . . . . . . . 15
8.2. ControllingAuthority . . . . . . . . . . . . . . . . . . . 17
9. Normative References . . . . . . . . . . . . . . . . . . . . . 17
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1. Introduction
This specification defines a new XML schema for thoroughly and
completely representing and sharing timezone information that is
consistent across platforms and software systems.
2. Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
The namespace "urn:ietf:params:xml:ns:timezones" is reserved for the
XML elements defined in this specification, its revisions, and
related specifications. XML elements defined by individual
implementations MUST NOT use the "urn:ietf:params:xml:ns:timezones"
namespace, and instead should use a namespace that they control.
In this specification, the prefix "TZ:" is used for the namespace URI
identified above.
The term "content item" denotes a typed data entity that is a basic
unit of sharing timezone information.
The term "tz xml" is used to describe the overall set of content
items and their relationships in defining timezone information. It
refers to the complete set of XML elements described in this
specification.
The term "user" denotes a single user, group of users, or registered
organization that shares knowledge of timezone information. Users
can be involved in authoring, providing or consuming timezone
information.
The term "service" denotes an application entity that facilitates the
storing and sharing of tz xml with other services or clients. A
service can facilitate authoring, providing or consuming of timezone
information. The entity represented by a service could be a web
application, a web server or something more precise such as a
specific application running on a specific device.
The term "client" denotes an application entity that requests
timezone information in order to properly handle time and timezones
in software applications. The entity represented by a client could
be an operating system, a server application, a client application or
a cloud service. The client endpoint interacts with the service
endpoint.
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3. Schema Definition
3.1. Common Requirements
The following requirements apply to all parts of this specification.
1. All date-time values MUST conform to the Date and Time
specification of [RFC3339], with the following added constraints:
* Times MUST be expressed in milliseconds.
* Times MUST be given in the UTC timezone, and end in "Z",
without a timezone offset.
2. All XML element and attribute tags are case-sensitive and must
appear in a Time Zone document as they appear in this
specification.
3.2. TZ:TimeZone XML element
The TZ:TimeZone element is the top-level element of any timezone
information document. It MUST contain several top-level, timezone
properties as well as one TZ:StandardTime element.
+--------------+----------------------------------------------------+
| Attribute | Description |
+--------------+----------------------------------------------------+
| ID | A required, string attribute. This is the unique |
| | ID of a timezone. |
| Revision | A required, integer attribute. The version number |
| | of the timezone. It SHOULD be incremented by one |
| | each time a change is made to any of the |
| | timezone's properties. |
| LastModified | A required, xsd:dateTime attribute. The date and |
| | time that the timezone data was last modified by |
| | any entity creating or saving data through a |
| | service. |
| Language | A required, xsd:language attribute. The language |
| | of any human-readable strings in the tz xml. |
| | These would be properties such as Name and |
| | Description. |
+--------------+----------------------------------------------------+
3.2.1. TZ:Name XML element within TZ:TimeZone
The TZ:Name element is an optional element within TZ:TimeZone. When
present, it corresponds to a human-readable name for the timezone.
It may be stored and returned in a number of different languages.
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See section :TODO for more information on International Strings for
TZ XML.
3.2.2. TZ:Description XML element within TZ:TimeZone
The TZ:Description element is an optional element within TZ:TimeZone.
When present, it corresponds to a human-readable description for the
timezone. It may be stored and returned in a number of different
languages. See section :TODO for more information on International
Strings for TZ XML.
3.2.3. TZ:InfoURL XML element within TZ:TimeZone
The TZ:InfoURL element is an optional element within TZ:TimeZone.
When present, it must have a valid xsd:anyURI value. The URL defined
here is used to reference a Web site or other Internet information
regarding the timezone.
3.2.4. TZ:CalendarScale XML element within TZ:TimeZone
The TZ:CalendarScale element within TZ:TimeZone is required and
represents the underlying calendar scale or calendar system that the
timezone definition is based on. An example of a TZ:CalendarScale is
"Gregorian". The value is case-insensitive.
3.2.5. TZ:ReferencedControllingAuthority XML element within TZ:TimeZone
The TZ:ReferencedControllingAuthority element within TZ:TimeZone is
required and represents the governing body that has authority to
change how time is observered in a given region. A timezone has one
and only one controlling authority. This element represents a
reference to a separate content item. See section :TODO for more
information on the TZ:ControllingAuthority content item.
+-----------+-------------------------------------------------------+
| Attribute | Description |
+-----------+-------------------------------------------------------+
| ID | A required, string attribute. This is the unique ID |
| | of the controlling authority. |
| Revision | A required, integer attribute. The version number of |
| | the controlling authority that is being referenced. |
| | Together with ID, this attribute provides a unique |
| | reference to a controlling authority. |
+-----------+-------------------------------------------------------+
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3.2.6. TZ:StandardTime XML element within TZ:TimeZone
The TZ:StandardTime element is required and denotes the timezones
regular offset from Universal Co-ordinated Time (UTC). Standard time
is observed whenever other exceptions to standard time (Daylight
Savings, European Summer Time) are not in effect. TZ:StandardTime
has a name, a base offset from UTC, date ranges that MAY denote
historical observances of the offset. See section :TODO for more
information on TZ:StandardTime and its child elements.
+-----------+-------------------------------------------------------+
| Attribute | Description |
+-----------+-------------------------------------------------------+
| ID | A required, string attribute. This value MUST be a |
| | unique element identifier within the timezone content |
| | item. The ID is used exclusively to identify |
| | human-readable, localizable element values within |
| | TZ:StandardTime |
+-----------+-------------------------------------------------------+
3.2.6.1. TZ:Name XML element within TZ:StandardTime
The TZ:Name element is required and represents the friendly, human-
readable display name of the timezone when standard time is observed.
3.2.6.2. TZ:BaseUtcOffset XML element within TZ:StandardTime
The TZ:BaseUtcOffset element is required and represents the number of
hours from UTC that the timezone observes when in standard time.
Since the base UTC offset can change for a timezone historically, TZ:
StandardTime can contain one-to-many TZ:BaseUtcOffset elements. The
value of the offset and the years that the offset was in effect are
expressed as child elements of TZ:BaseUtcOffset.
3.2.6.2.1. TZ:BaseUtcOffsetValue XML element within TZ:BaseUtcOffset
The TZ:BaseUtcOffsetValue element denotes the value of the offset
from UTC for an observance of a timezone. It uses the requires the
format HH:MM:SS.MMM. A minus (-) symbol is used to express a local
time occurring before UTC. For example, standard time in the Eastern
Time Zone of the United States is expressed as the offset value -05:
00:00.000.
3.2.7. TZ:StandardTimeChange XML element within TZ:TimeZone
The TZ:StandardTimeChange element is optional and MAY represent any
changes to a timezone's regular standard time observance. Examples
of this include Daylight Savings Time in the United States or Summer
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Time in Europe where the observed offset from UTC for a timezone
shifts by an hour to conserve daylight. TZ:StandardTimeChange has a
name, a value that represents the change from standard time and a
number of rules that express when transitions to this change occur.
See section :TODO for more information on TZ:StandardTimeChange and
its child elements.
+-----------+-------------------------------------------------------+
| Attribute | Description |
+-----------+-------------------------------------------------------+
| ID | A required, string attribute. This value MUST be a |
| | unique element identifier within the timezone content |
| | item. The ID is used exclusively to identify |
| | human-readable, localizable element values within |
| | TZ:StandardTimeChange (like TZ:Name for example). |
+-----------+-------------------------------------------------------+
3.2.7.1. TZ:Name XML element within TZ:StandardTimeChange
The TZ:Name element is required and represents the friendly, human-
readable display name of the timezone when a change to standard time
is in effect. For example, Pacific Daylight Time.
3.2.7.2. TZ:OffsetChange XML element within TZ:StandardTimeChange
The TZ:OffsetChange element denotes the delta or change from the base
UTC offset observed during this change to standard time. The value
of the offset change requires the format HH:MM:SS.MMM. A minus (-)
symbol is used to express a change to the base offset that is less
than the standard UTC offset. UTC. For example, daylight time in
the Eastern Time Zone of the United States is expressed as a change
by one hour to the base UTC offset of -05:00:00.000. So the offset
change would be -01:00:00.000.
3.3. TZ:EffectiveYearRange XML element
The TZ:EffectiveYearRange element appears within TZ:BaseUtcOffset and
within TZ:OffsetChange and contains information referring to the
effective range of a base UTC offset or offset change. The StartYear
and EndYear attributes dictate the range of years.
+-----------+-------------------------------------------------------+
| Attribute | Description |
+-----------+-------------------------------------------------------+
| StartYear | A required, integer attribute. This represents the |
| | year that the offset began to take effect. It MUST |
| | be a positive integer. |
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| EndYear | A required, integer attribute. This represents the |
| | year that the offset ceased being valid. It MUST be |
| | a positive integer. |
+-----------+-------------------------------------------------------+
3.3.1. TZ:TransitionPeriod XML element within TZ:EffectiveYearRange
The TZ:TransitionPeriod element contains specific rules for a
transition. They ultimately express moments in time. These rules
have the following requirements:
o Together, they define a moment in time for a transition
o They have a granularity of milliseconds
o Transition rules include expressions for Month, DayOfMonth,
DayOfWeek and TimeOfDay.
o They define the effective date of a transition by using comparison
operators. It is not intended that the expressions would define
an effective range of an observance, so rules should not be geared
toward a range of time. To understand the start and end date of
an observance, you must parse the effective range information.
o There are no default values assumed; you should be explicit about
each piece.
o The expression of rules is very flexible, but it should be
optimized to be as small a data set as is necessary to represent a
transition point. Use ranges of years whenever possible to keep
the data set small.
o Cardinality is 0-N for expressions. Because of the flexibility,
it is possible for authors to write rules that don't make sense or
are missing critical pieces of information. An implementation of
the service SHOULD check for unwanted conditions and send warning
messages or tips.
3.3.1.1. TZ:Start and TZ:End XML elements within TZ:TransitionPeriod
The TZ:Start element contains child elements that define when a
transition starts. The TZ:End element defines when a transition
period ends.
3.3.1.1.1. TZ:Month XML element within TZ:Start or TZ:End
TZ:Month defines a month of the year in which a transition period
starts or ends.
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+-----------+-------------------------------------------------------+
| Attribute | Description |
+-----------+-------------------------------------------------------+
| Value | A required, integer attribute. The numeric value |
| | starts at 1 for the first month of the year. In |
| | Gregorian scale, 1 = January. It MUST be a positive |
| | integer. |
+-----------+-------------------------------------------------------+
3.3.1.1.2. TZ:DayOfMonth XML element within TZ:Start or TZ:End
TZ:DayOfMonth defines a day of the month in which a transition period
starts or ends.
+-----------+-------------------------------------------------------+
| Attribute | Description |
+-----------+-------------------------------------------------------+
| Value | A required, integer attribute. For example in April, |
| | the days of the months would range in value from 1-31 |
| | for the Gregorian calendar. |
+-----------+-------------------------------------------------------+
3.3.1.1.3. TZ:DayOfWeek XML element within TZ:Start or TZ:End
TZ:DayOfWeek element defines a weekday that a transition period would
start or end. This is used specifically when defining relative start
and end times (for example, second Sunday in October in the Gregorian
calendar).
+-------------------+-----------------------------------------------+
| Attribute | Description |
+-------------------+-----------------------------------------------+
| Value | A required, integer attribute. The numeric |
| | value starts with 1 for the first day of the |
| | week. In Gregorian scale, 7 = Sunday, for |
| | example. |
| OccurrenceInMonth | An optional, integer attribute. Used in |
| | DayOfWeek rules only. It takes the value set |
| | +/-N occurrence in the month. For example, a |
| | -1 value is the last occurrence of a certain |
| | day of the week in the month specified. -2 |
| | would be the second to last specified day of |
| | the week in the month specified. See section |
| | :TODO for an example of its usage. |
+-------------------+-----------------------------------------------+
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The following XML fragment represents the "first Sunday in April" in
the Gregorian calendar:
3.3.1.1.4. TZ:TimeOfDay XML element within TZ:Start or TZ:End
TZ:TimeOfDay element defines a clock time in a day.
+-----------+-------------------------------------------------------+
| Attribute | Description |
+-----------+-------------------------------------------------------+
| Value | A required, string attribute. The time of day value |
| | is to milliseconds granularity, like 02:00:00.000. |
| | Leading and trailing zeros are required. The format |
| | is HH:MM:SS.MMM |
+-----------+-------------------------------------------------------+
3.4. TZ:ControllingAuthority XML element
This object is defined as a political body or government that has
political control over the definition of a timezone
o TZ:Name and TZ:Description elements human-readable information
about the controlling authority content item
+--------------+----------------------------------------------------+
| Attribute | Description |
+--------------+----------------------------------------------------+
| ID | A required, string attribute. This is the unique |
| | ID of a controlling authority. |
| Revision | A required, integer attribute. The version number |
| | of the controlling authority. It SHOULD be |
| | incremented by one each time a change is made to |
| | any of the controlling authority's properties. |
| LastModified | A required, xsd:dateTime attribute. The date and |
| | time that the controlling authority data was last |
| | modified by any entity creating or saving data |
| | through a service. |
| Language | A required, xsd:language attribute. The language |
| | of any human-readable strings in the tz xml. |
| | These would be properties such as Name and |
| | Description of the controlling authority. |
+--------------+----------------------------------------------------+
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4. Example TZ XML
This example of tz xml demonstrates the format of timezone
information described in this specification.
Example: Pacific Time Zone in North America.
Pacific Standard Time
(UTC-08:00) Pacific Time (US & Canada)
http://tz.example.com/us/pacific
Gregorian
Pacific Standard Time
-08:00:00.000
Pacific Daylight Time
+01:00:00.000
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5. Security Considerations
TBD
6. IANA Considerations
This document defines a new URN to identify a new XML namespace for
timezone data. The URN conforms to a registry mechanism described in
[RFC3688].
This document defines a new media type. The registration is in
Section 6.2.
6.1. Namespace Registration
Registration request for the timezone namespace:
URI: urn:ietf:params:xml:ns:timezone
Registrant Contact: See the "Authors' Addresses" section of this
document.
XML: None. Namespace URIs do not represent an XML specification.
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6.2. Media Type
This section defines the MIME media type for use with timezone XML
data.
To: ietf-types@iana.org
Subject: Registration of media type application/timezone+xml
Type name: application
Subtype name: timezone+xml
Required parameters: none
Optional parameters: charset
Encoding considerations: timezone data is typically UTF-8 and thus
the XML representation will follow that. As a result, for 7-bit
transports, data in UTF-8 MUST be encoded in quoted-printable or
base64.
Security considerations: See Section 5.
Interoperability considerations: This media type provides a syntax
for timezone data based on XML.
Published specification: This specification.
Applications which use this media type: Calendaring and scheduling.
Additional information:
Magic number(s): None
File extension(s): XML data should use "xml" as the file
extension.
Macintosh file type code(s): None specified.
Person & email address to contact for further information: See the
"Author's Address" section of this document.
Intended usage: COMMON
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Restrictions on usage: There are no restrictions on where this media
type can be used.
Author: See the "Author's Address" section of this document.
Change controller: IETF
7. Acknowledgements
This specification was suggested by discussion that took place within
the Calendaring and Scheduling Consortium's Timezone Technical
Committee. The authors thank the participants of that group for
their input. In particular, the main design of this schema was
provided by Bryan Keller, Quincy Milton, Derek Shaw, and Durgaprasad
Gorti.
8. Appendix A: RelaxNG Schemas for TZ XML
The following includes Relax NG compact schemas for the TZ XML
content items.
8.1. TimeZone
Time Zone RNC
default namespace tz="urn:ietf:params:xml:ns:timezones"
## This format is returned in a call to GET a specific timezone
## and revision
## If language is not specified on the URL request, certain optional
## fields are not returned
## GET /timezones/{id}/{rev}
start =
element TZ:TimeZone {
attribute ID { xsd:integer }&
attribute LastModified { xsd:dateTime }&
attribute Language { xsd:language }?&
element TZ:InfoUrl { xsd:anyURI }&
element TZ:ControllingAuthority {
attribute ID { text }&
attribute Revision { xsd:integer }
}&
element TZ:CalendarScale { text }&
## Returned when language query parameter is
## set ?language=en-us, for example
element TZ:Name { text }?&
element TZ:Description { text }?&
## end comment
element TZ:StandardTime {
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attribute ID { text }&
## Returned when language query parameter is
## set ?language=en-us, for example
element TZ:Name { text }?&
## end comment
element TZ:BaseUtcOffset {
element TZ:BaseUtcOffsetValue { text }&
EffectiveYearRange+
}+
}&
element TZ:StandardTimeChange {
attribute ID { text }&
## Returned when language query parameter is
## set ?language=en-us, for example
element TZ:Name { text }?&
## end comment
element TZ:OffsetChange { text }&
EffectiveYearRange+
}*&
}
EffectiveYearRange =
element TZ:EffectiveYearRange {
attribute EndYear { xsd:integer }&
attribute StartYear { xsd:integer }&
element TZ:TransitionPeriod {
element TZ:Start { Month, DayOfMonth?, DayOfWeek, TimeOfDay }&
element TZ:End { Month, DayOfMonth?, DayOfWeek, TimeOfDay }
}+
}
Month =
element TZ:Month {
attribute Value { xsd:integer }
}
DayOfMonth =
element TZ:DayOfMonth {
attribute Value { xsd:integer }
}
DayOfWeek =
element TZ:DayOfWeek {
attribute OccurrenceInMonth { xsd:integer }?&
attribute Value { xsd:integer }?
}
TimeOfDay =
element TZ:TimeOfDay {
attribute Value { text }
}
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8.2. ControllingAuthority
ControllingAuthority RNC
default namespace tz="urn:ietf:params:xml:ns:timezones"
## GET when language is specified on the URL
## /controllingauthorities/{id}/{rev}?language=en-us
start =
element TZ:ControllingAuthority {
attribute ID { xsd:integer }&
attribute LastModified { xsd:dateTime }&
attribute Revision { xsd:integer }&
attribute Language { xsd:language }?&
element TZ:Name { text }?&
element TZ:Description { text }?
}
9. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3339] Klyne, G., Ed. and C. Newman, "Date and Time on the
Internet: Timestamps", RFC 3339, July 2002.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
January 2004.
Authors' Addresses
Michael Douglass
Rensselaer Polytechnic Institute
110 8th Street
Troy, NY 12180
USA
EMail: douglm@rpi.edu
URI: http://www.rpi.edu/
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Cyrus Daboo
Apple Inc.
1 Infinite Loop
Cupertino, CA 95014
USA
EMail: cyrus@daboo.name
URI: http://www.apple.com/
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