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This document was prepared by Technical Committee LOCALIZATION.
A number of international applications require the identification of written language conversion systems, including for terminology, lexicography, bibliography, and linguistics, especially for reverse transliteration, computational linguistics and machine pronunciation.
This document sets out the necessary procedures to maintain the registry of written language conversion systems.
The chosen term “written language conversion” is intended to refer to all types of conversions, i.e. transformations of written texts from one spelling system to another. It thus includes both script conversion (change of script: transliteration, transcription) and conversion of texts without changing the script (e.g. transcription of foreign names or words using the alphabet of a target language, change of the orthography in a language, etc.). For the sake of compactness of expression, “written language conversion” has been shortened to “conversion” in this document where it does not cause ambiguity.
This document provides principles for establishing codes for the representation of written language conversion systems.
The codes are devised for usage in any application requiring the expression of written language conversion systems, including transliteration and romanization systems, in coded form.
For the purposes of this document, the terms and definitions given in
particular graphic representation or class of representations of a set of characters used to write one or more languages
set of rules governing the orthography of a language
Typically, a spelling system defines how the spoken form of a language is represented in writing. Several languages have undergone orthographic reforms which means they have had different spelling systems.
language which is or was in active use in a community of people, and the rules of which are mainly deduced from the usage
member of a set of elements that is used for the representation, organization, or control of data
process whereby one
This is a general term that includes script conversion but also, e.g., cases when a language changes its orthography without changing the script.
process which consists of representing the characters of an alphabetical or syllabic system of writing by the characters of a conversion alphabet
process whereby the sounds of a given language are noted by the system of signs of a conversion language
script conversion from non-Roman to Roman {Latn} by means of
set of rules for
combination of characters used to represent the name of a language (
combination of characters used to represent the name of a {Latn}
combination of characters used in a structured way to represent a
A conversion system code shall consist of four segments:
titular segment;
source spelling system segment;
target spelling system segment;
identifying segment.
Each segment SHALL consist of one or more elements.
The following rules are to be adhered to for the construction of a conversion system code:
The codes shall consist of elements from the following Unicode ranges:
DIGIT ZERO through DIGIT NINE (U+0030 — U+0039)
LATIN CAPITAL LETTER A through LATIN CAPITAL LETTER Z (U+0041 — U+005A)
LATIN SMALL LETTER A through LATIN SMALL LETTER Z (U+0061 — U+007A)
Segments shall be separated by a single “COLON” (“:”, Unicode U+003A).
Elements within a segment shall be separated by a single “HYPHEN-MINUS” (“-”, Unicode U+002D).
“HYPHEN-MINUS” (“-”, Unicode U+002D) within an element (e.g. 233-3) will also be accepted.
Other characters in the elements not covered by the above should be omitted or substituted.
This part will contain a reference to the conversion system authority or authorities by using identifiers, the list of which is maintained by ISO 24229/RA (
Except as specified in
language code (3-letter code from
script code (4-letter code from
country code (2-letter code from
spelling system extension (an ad hoc string to refer to a non-default spelling system of a language, such as old orthography).
ind-Latn-pre1972 (Indonesian language using the pre-1972 orthography)
bos-Arab (Bosnian language using Arabic script)
uzb-Arab-AF (Uzbek language as used in Afghanistan)
This part may have the same four elements as listed in
This part will serve to distinguish by version, year of issue, etc. conversion systems that otherwise have the same scope. It may also contain elements necessary for the recognition of the system itself if the system has some kind of identification element. All in all, the following elements may occur (in the order given):
identifying numbers, letters or else (such as standard number, e.g. 843)
version number (e.g. v6, v4-1)
year of adoption
year of issue
method identifier (if a standard devises more than one method of conversion, this optional ad hoc identifier could be used for distinction)
If there are cases when no elements can be used for this part, na (not applicable) will be the substitute.
2017 is the identifying segment of the system coded as UN:ara-Arab:Latn:2017.
Additions to the list of conversion system codes shall be made on the basis of information from upon the request of a member of ISO 24229/AG (
The ISO 24229/AG will decide upon the addition, on the basis of the justification given for the actual requirements for international interchange. Code elements will be allocated accordingly.
A written language conversion system is eligible for a conversion system code assignment if it fulfils one of the following criteria.
The system has been approved for official use at some level of government.
The system has been developed and used by educational/scientific institutions, published in a peer reviewed scientific publication.
The system has been in substantial usage.
Assigning of a conversion system code also requires demonstration of one of the following usage factors:
necessity of identification of the system in interchange.
necessity of identification of the system in data encoding.
Systems that are used in isolation or only for temporary usage do not need to have assigned codes.
Deprecation of conversion system codes shall be made upon request of a member of ISO 24229/AG or the conversion system authority that manages the system.
The ISO 24229/AG will decide upon the marking of deprecation, on the basis
of the information received. The corresponding code is reserved
for backwards-compatibility. Deprecation only applies to the code representation of the written languages conversion system, and not the system itself. For example, deprecation may be necessary when the authority undergoes a rename.
If users need codes to represent conversion systems
not included in the conversion system registry, the code prefix of zz
can be used, which must be placed at the beginning of the conversion system code,
in the titular segment, and followed by a “HYPHEN MINUS” character (“-”,
Unicode U+002D). Users are advised that the above series of codes are not universally used, those code elements are not compatible between different entities.
Conversion system codes will use capitalization according to the relevant standards but this does not have any distinctive meaning. For example, an all lower case code will be an equally valid code.
In case of user demand, abbreviated conversion system codes may additionally be registered whereby in identifying language-specific spelling systems script codes are omitted if they can be considered as default scripts for the languages concerned. Examples are given in
The examples given here are only indicative and do not guarantee that such codes will be actually registered.
UN:ara-Arab:Latn:2017 (possible abbreviation — UN:ara:Latn:2017; United Nations system for the romanization of Arabic, approved 2017)
UN:mon-Mong-CN:Latn:1977 (possible abbreviation — UN:mon-CN:Latn:1977; United Nations system for the romanization of Mongolian in China, approved 1977)
BGN-PCGN:chn-Hans:Latn:1979 (BGN/PCGN 1979 Agreement — Romanization of Chinese)
ALA-LC:mal-Mlym:Latn:2012 (possible abbreviation — ALA-LC:mal:Latn:2012; ALA-LC romanization system that transliterates the Malayam language from Malayam script characters into Latin script)
ISO:Cyrl:Latn:9-1995 (
ICAO:Arab:Latn:2015 (ICAO rules for rendering Arabic-script names in Latin letters, issued in 2015)
DIN:bel-Cyrl:Latn:1460-1982 (possible abbreviation — DIN:bel:Latn:1460-1982;
ESKT:udm-Cyrl:est-Latn:2021 (possible abbreviation — ESKT:udm:est:2021; Estonian Language Committee’s rules for rendering Udmurt names in Estonian texts, approved 2021)
LV:eng-Latn:lav-Latn:2006 (possible abbreviation — LV:eng:lav:2006; official instructions in Latvia on rendering English proper names in Latvian, issued in 2006)
Target spelling systems can also be language-specific.
A conversion system authority is a competent authority that creates, publishes and/or manages written language conversion systems.
Authorities that are no longer competent will depend on ISO 24229/AG for managing codes, which will be considered on a case-by-case basis.
A conversion system authority should:
have at least one written language conversion system eligible for a conversion system code;
be competent in managing its written language conversion systems (
If a conversion system authority does not meet requirements outlined in
The “Varia systems” (Var) conversion system authority is managed by ISO 24229/AG to represent written language conversion systems that:
have a need to be represented as determined by ISO 24229/AG;
yet do not have a clear extant authority.
A competent conversion system authority is a recognized institution that has standardized processes surrounding the management of the written language conversion systems, covering the following processes:
planning of written language conversion systems, including the process of designing and defining written language conversion systems; and
performing changes to written language conversion systems are well planned.
It is recommended for a competent conversion system authority to also establish standardized processes for the following:
public announcement and dissemination of its written language conversion systems; and
allows a public review period for people affected by written language conversion systems under its management prior to enactment.
The ISO 24229/AG is tasked with managing a list of conversion system authorities.
The principle behind the alphabetic identifiers for conversion system authorities is a visual association between the conversion system authorities’ names and their corresponding identifiers.
In applying this principle, the identifiers will be generally assigned on the basis of the abbreviated names of the conversion system authorities, thus avoiding, wherever possible, any reflection of their political status.
The following rules shall be adhered to for the construction of the alphabetic identifier:
The maximum length of the identifier shall be 16 characters.
The identifier shall consist of elements from the following Unicode ranges:
DIGIT ZERO through DIGIT NINE (U+0030 — U+0039)
LATIN CAPITAL LETTER A through LATIN CAPITAL LETTER Z (U+0041 — U+005A)
LATIN SMALL LETTER A through LATIN SMALL LETTER Z (U+0061 — U+007A)
The identifier elements shall be separated by a single HYPHEN-MINUS (U+002D).
The minimal length of the identifier is 3 characters to encourage the creation of descriptive and distinguishable elements, with the exception of the following:
UN, for United Nations
Identifiers with 2 characters shall be reserved for codes in
Conversion system authority identifiers will use capitalization like in ordinary abbreviations, but this does not have any distinctive meaning. For example, an all lower case identifier will be an equally valid identifier.
The examples given here are only indicative.
ISO for International Organization for Standardization
BGN-PCGN for the United States Board on Geographic Names — Permanent Committee on Geographical Names for British Official Use
ALA-LC for American Library Association — Library of Congress
DIN for German Institute for Standardization
ICAO for International Civil Aviation Organization
UN for United Nations
The data models in this clause shall be used by other data models specified in this document.
iso15924Code represents code elements from
iso639Code represents code elements from
iso3166Code represents country codes from
iso8601Expression represents datetime expressions that conform with
An identifier that represents the conversion system authority (
The identifiable short name that uniquely identifies the conversion system authority.
Any further notes.
Either a 2-letter iso3166Code, or a String under the constraints of
A code that identifies the written language conversion system.
A name that represents the written language conversion system.
The conversion system authority under which this conversion system belongs.
The spelling system used in the source text.
The spelling system used in the output text.
An identifier that distinguishes the written languages conversion system from others with the same conversion system authority and spelling scopes.
Written language conversion systems can be related to other written language conversion systems in a number of ways. For example, a written language conversion system may represent an adoption or variant of another written language conversion system.
Hierarchical structures of written language conversion systems can be constructed by means of relationships.
This element is optional.
An optional code that identifies the current status of the conversion system code itself.
An optional code that identifies the current status of the written language conversion system itself.
Any further notes.
The date of the adoption of the written language conversion system by the authority may be noted in the remarks.
A typical use case is to show its original code from the original system from where this code has been imported.
NOTE: OGC 11-122r1 code urd_Arab2Latn_ODNI_2004
scriptCode shall be present. In the case of a language-specific spelling system, languageCode is also required.
A 3-letter code from
A 4-letter code from
An optional 2-letter code from
An optional ad hoc string to refer to a non-default spelling system of a language.
The conversion system of which this relation is a target.
One or more types of relation that the conversion system has with the target conversion system.
Examples of system code statuses:
The current system code is marked as “preferred”.
The current system code is marked as “deprecated”. The deprecation marker in no way indicates deprecation of the system itself.
When a conversion system code has been renamed, maybe due to the renaming of the corresponding system authority, then the old code can be considered “deprecated” in favour of the renamed code. The conversion system itself remains unchanged.
Examples of system statuses:
The current system is marked as “former”.
The current system is marked as “current”.
The current system is marked as “inactive”.
When it has been deprecated of its own accord, it can be considered “inactive”.
Examples of relation types:
The current system is based on the target system. The conversion process inherits certain attributes from the target system.
ALA-LC:jpn-Hrkt:Latn:1997 is based on Var:jpn-Hrkt:Latn:Hepburn-1886.
The target system is based on the current system. It can be thought of as the inverse of basedOn.
Var:jpn-Hrkt:Latn:Hepburn-1886 is the basis for ALA-LC:jpn-Hrkt:Latn:1997, BGN:jpn-Hrkt:Latn:1930, BGN-PCGN:jpn-Hrkt:Latn:1976 and BGN-PCGN:jpn-Hrkt:Latn:2017
The current system is an alias to the target system. The conversion processes are identical.
The current system is adopted from the target system. The conversion processes may not be identical.
The current system supersedes the target system.
The current system is superseded by the target system.
The current system is related to the target system.
For the purpose of registering conversion system codes and conversion system authority identifiers, ISO has designated a Registration Authority for ISO 24229.
The name and contact information of the Registration Authority for this document can be found at
The ISO list identifies the Registration Authority and where the Registration Authority has published materials related to this document on the Internet.
It has been entrusted with the following functions with regard to the list of conversion system authorities and written language conversion systems, together with code assignments and information associated with each entry:
to add and eliminate these entries, in accordance with the rules in this document;
to advise users and ISO member bodies regarding application of such information;
to update and disseminate such information;
to maintain a reference list of such information;
to publish changes made to such information and the history of changes allowing traceability;
to administer the reservation of the codes.
Changes to the content of the list of entries becomes effective immediately upon publication.
The criteria provided in
The RA will provide at least the following data on conversion system codes:
the conversion system code
the name of the conversion system and its authority
the source language and script of the conversion system
the target language and script of the conversion system
the source bibliographic reference
method identifier of the conversion system
status of the conversion system code
relationship with other conversion systems
any associated remarks
For the purpose of increasing transparency and making sure the operations of the registration authority (ISO 24229/RA) are carried out in accordance with guidelines provided in this document, the registration authority will appoint an advisory group of at least 4 members and up to 12 members.
The advisory group will consist of experts knowledgeable in the fields of script or other type of conversions, information technologies, library management. The group will also contain a representative of TC 46 and may also contain representatives of organizations interested in using the conversion system codes.
As a rule, the advisory group will make its decisions by consensus. If a vote is needed, the decision is approved when more than two-thirds of members vote for it.
Additions to the list of conversion system authority identifiers shall be made on upon request from a member of the ISO 24229/AG.
A conversion system authority is eligible for registration if it meets the requirements stated in
The proposer is responsible for providing justification to the ISO 24229/AG regarding the eligibility of such addition.
The ISO 24229/AG will decide upon the addition, on the basis of eligibility and usage justification.
Identifiers will be allocated by the ISO 24229/AG at its discretion.
A conversion system authority can be marked inactive by ISO 24229/AG if the authority ceases to exist or no longer wishes to register its written language conversion systems.
Such inactive status shall be considered by the ISO 24229/AG upon request from the conversion system authority itself or a member of the ISO 24229/AG.
The ISO 24229/AG at its sole discretion, will determine what information will remain on the basis of practicality and continuity of usage.
Modifications of an entry within the list of conversion system authority identifiers shall be made upon the request of a member of ISO 24229/AG or the conversion system authority that manages the system.
The ISO 24229/AG will decide upon the modification, on the basis of the information received.
The previously assigned identifier will be reserved after modification for backwards-compatibility purposes.
Modifications to a registered element shall be made upon requests from a member of the ISO 24229/AG or the conversion system authority that manages the system.
A significant change of name may require the ISO 24229/AG to change the identifier concerned. The ISO 24229/AG, however, shall endeavour to maintain stability in the list of identifiers.
If a conversion system authority is marked inactive, the responsibility of maintaining its written language conversion system entries are assumed by ISO 24229/AG.
The “Varia systems” conversion system authority is assigned the identifier Var. In this case, ISO 24229/AG will manage written language conversion systems with need for representation, but which do not have a clear authority.
The Wade-Giles Chinese transcription system from
Alterations to a registered element shall be made only upon request of a member of ISO 24229/AG or the conversion system authority that manages the system.
A significant change of name may require the ISO 24229/AG to change the alpha code element concerned. The ISO 24229/AG, however, shall endeavor to maintain stability in the list of code elements.
Some code elements managed by ISO 24229/RA are reserved:
for a limited period when their reservation is the result of the deprecation (
for an indeterminate period when the reservation is the result of the application of international law or of exceptional requests (
Code elements that the ISO 24229/AG has altered or deleted should not be reallocated indefinitely.
Code elements may be reserved, in exceptional cases, for conversion systems authorities and written language conversion systems which the ISO 24229/AG has decided not to include in the lists maintained by ISO 24229/RA, but for which an interchange or encoding requirement exists.
Before reallocating a former code element or a formerly reserved code element, the ISO 24229/AG shall consult, as appropriate, the authority or agency on whose behalf the code element was reserved, and consideration shall be given to difficulties which can arise from the reallocation.
A list of reserved code elements is kept by the ISO 24229/RA.
The ISO 24229/AG is available for consultation and assistance on the use of codes for conversion system authorities and written language conversion systems.
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.