Guidance on Designing Label Generation Rulesets (LGRs) Supporting Variant Labels
RFC 8228
| Document | Type |
RFC - Informational
(August 2017; Errata)
Was draft-freytag-lager-variant-rules (individual in art area)
|
|
|---|---|---|---|
| Last updated | 2019-03-25 | ||
| Stream | IETF | ||
| Formats | plain text pdf html bibtex | ||
| Reviews | |||
| Stream | WG state | (None) | |
| Document shepherd | Scott Hollenbeck | ||
| Shepherd write-up | Show (last changed 2017-04-17) | ||
| IESG | IESG state | RFC 8228 (Informational) | |
| Consensus Boilerplate | No | ||
| Telechat date | |||
| Responsible AD | Alexey Melnikov | ||
| Send notices to | "Scott Hollenbeck" <shollenbeck@verisign.com> | ||
| IANA | IANA review state | Version Changed - Review Needed | |
| IANA action state | No IANA Actions | ||
Internet Engineering Task Force (IETF) A. Freytag
Request for Comments: 8228 August 2017
Category: Informational
ISSN: 2070-1721
Guidance on Designing Label Generation Rulesets (LGRs) Supporting
Variant Labels
Abstract
Rules for validating identifier labels and alternate representations
of those labels (variants) are known as Label Generation Rulesets
(LGRs); they are used for the implementation of identifier systems
such as Internationalized Domain Names (IDNs). This document
describes ways to design LGRs to support variant labels. In
designing LGRs, it is important to ensure that the label generation
rules are consistent and well behaved in the presence of variants.
The design decisions can then be expressed using the XML
representation of LGRs that is defined in RFC 7940.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Engineering Task Force
(IETF). It has been approved for publication by the Internet
Engineering Steering Group (IESG). Not all documents approved by the
IESG are a candidate for any level of Internet Standard; see
Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc8228.
Freytag Informational [Page 1]
RFC 8228 Variant Rules August 2017
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Variant Relations . . . . . . . . . . . . . . . . . . . . . . 4
3. Symmetry and Transitivity . . . . . . . . . . . . . . . . . . 5
4. A Word on Notation . . . . . . . . . . . . . . . . . . . . . 5
5. Variant Mappings . . . . . . . . . . . . . . . . . . . . . . 6
6. Variant Labels . . . . . . . . . . . . . . . . . . . . . . . 7
7. Variant Types and Label Dispositions . . . . . . . . . . . . 7
8. Allocatable Variants . . . . . . . . . . . . . . . . . . . . 8
9. Blocked Variants . . . . . . . . . . . . . . . . . . . . . . 9
10. Pure Variant Labels . . . . . . . . . . . . . . . . . . . . . 10
11. Reflexive Variants . . . . . . . . . . . . . . . . . . . . . 11
12. Limiting Allocatable Variants by Subtyping . . . . . . . . . 12
13. Allowing Mixed Originals . . . . . . . . . . . . . . . . . . 14
14. Handling Out-of-Repertoire Variants . . . . . . . . . . . . . 15
15. Conditional Variants . . . . . . . . . . . . . . . . . . . . 16
16. Making Conditional Variants Well Behaved . . . . . . . . . . 18
17. Variants for Sequences . . . . . . . . . . . . . . . . . . . 19
18. Corresponding XML Notation . . . . . . . . . . . . . . . . . 21
19. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22
20. Security Considerations . . . . . . . . . . . . . . . . . . . 23
21. References . . . . . . . . . . . . . . . . . . . . . . . . . 23
21.1. Normative References . . . . . . . . . . . . . . . . . . 23
21.2. Informative References . . . . . . . . . . . . . . . . . 23
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 24
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 24
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RFC 8228 Variant Rules August 2017
1. Introduction
Label Generation Rulesets (LGRs) that define the set of permissible
labels may be applied to identifier systems that rely on labels, such
as the Domain Name System (DNS) [RFC1034] [RFC1035]. To date, LGRs
have mostly been used to define policies for implementing
Internationalized Domain Names (IDNs) using IDNA2008 [RFC5890]
[RFC5891] [RFC5892] [RFC5893] [RFC5894] in the DNS. This document
aims to discuss the generation of LGRs for such circumstances, but
the techniques and considerations here are almost certainly
applicable to a wider range of internationalized identifiers.
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