ISO/IEC 8824-1:2021

INTERNATIONAL ISO/IEC
STANDARD 8824-1
Sixth edition
2021-06
Information technology — Abstract
Syntax Notation One (ASN.1) —
Part 1:
Specification of basic notation
Technologies de l'information — Notation de syntaxe abstraite
numéro un (ASN.1) —
Partie 1: Spécification de la notation de base
Reference number
ISO/IEC 8824-1:2021(E)
©
ISO/IEC 2021

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ISO/IEC 8824-1:2021(E)

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ii © ISO/IEC 2021 – All rights reserved

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ISO/IEC 8824-1:2021(E)
Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are
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Attention is drawn to the possibility that some of the elements of this document may be the subject of
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of any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents) or the IEC list of patent
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For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
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see www.iso.org/iso/foreword.html. In the IEC, see www.iec.ch/understanding-standards.
This document was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 6, Telecommunications and information exchange between systems, in collaboration
with ITU-T. The identical text is published as ITU-T X.680 (02/2021).
This sixth edition cancels and replaces the fifth edition (ISO/IEC 8824-1:2015), which has been
technically revised. It also incorporates ISO/IEC 8824-1:2015/Amd 1:2019, ISO/IEC 8824-1:2015/
Cor 1:2017, ISO/IEC 8824-1:2015/Cor 2:2018, ISO/IEC 8824-1:2015/Cor 3:2018.
A list of all parts in the ISO/IEC 8824 series can be found on the ISO and IEC websites.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html and www.iec.ch/national-
committees.
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ISO/IEC 8824-1:2021(E)
CONTENTS
Page
Introduction . viii
1 Scope . 1
2 Normative references . 1
2.1 Identical Recommendations | International Standards . 1
2.2 Additional references . 2
3 Definitions . 2
3.1 International Object Identifier tree specification . 2
3.2 Information object specification . 2
3.3 Constraint specification . 3
3.4 Parameterization of ASN.1 specification . 3
3.5 Structure for identification of organizations . 3
3.6 Universal Multiple-Octet Coded Character Set (UCS) . 3
3.7 Representation of dates and times . 3
3.8 Additional definitions . 4
4 Abbreviations . 9
5 Notation . 9
5.1 General . 9
5.2 Productions . 10
5.3 The alternative collections . 10
5.4 Non-spacing indicator . 10
5.5 Example of a production . 10
5.6 Layout . 10
5.7 Recursion . 11
5.8 References to permitted sequences of lexical items . 11
5.9 References to a lexical item . 11
5.10 Short-hand notations . 11
5.11 Value references and the typing of values . 12
6 The ASN.1 model of type extension . 12
7 Extensibility requirements on encoding rules . 12
8 Tags . 13
9 Encoding instructions . 14
10 Use of the ASN.1 notation . 15
11 The ASN.1 character set . 15
12 ASN.1 lexical items . 16
12.1 General rules . 16
12.2 Type references . 17
12.3 Identifiers . 17
12.4 Value references . 17
12.5 Module references . 17
12.6 Comments . 17
12.7 Empty lexical item . 18
12.8 Numbers . 18
12.9 Real numbers . 18
12.10 Binary strings . 18
12.11 XML binary string item . 18
12.12 Hexadecimal strings . 18
12.13 XML hexadecimal string item . 19
12.14 Character strings. 19
12.15 XML character string item . 20
12.16 The simple character string lexical item . 22
Rec. ITU-T X.680 (02/2021) iii
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ISO/IEC 8824-1:2021(E)
12.17 Time value character strings . 22
12.18 XML time value character string item . 22
12.19 The property and setting names lexical item . 22
12.20 Assignment lexical item . 22
12.21 Range separator . 22
12.22 Ellipsis . 22
12.23 Left version brackets . 23
12.24 Right version brackets . 23
12.25 Encoding references . 23
12.26 Integer-valued Unicode labels . 23
12.27 Non-integer Unicode labels . 23
12.28 XML end tag start item . 23
12.29 XML single tag end item . 23
12.30 XML boolean true item . 23
12.31 XML boolean extended-true item . 24
12.32 XML boolean false item . 24
12.33 XML boolean extended-false item . 24
12.34 XML real not-a-number item . 24
12.35 XML real infinity item . 24
12.36 XML tag names for ASN.1 types . 25
12.37 Single character lexical items . 26
12.38 Reserved words . 26
13 Module definition . 27
14 Referencing type and value definitions . 31
15 Notation to support references to ASN.1 components . 32
16 Assigning types and values . 33
17 Definition of types and values . 35
18 Notation for the boolean type . 38
19 Notation for the integer type . 38
20 Notation for the enumerated type . 39
21 Notation for the real type . 41
22 Notation for the bitstring type . 42
23 Notation for the octetstring type . 44
24 Notation for the null type . 44
25 Notation for sequence types . 45
26 Notation for sequence-of types . 48
27 Notation for set types . 50
28 Notation for set-of types . 51
29 Notation for choice types . 52
30 Notation for selection types . 54
31 Notation for prefixed types . 54
31.1 General . 54
31.2 The tagged type . 55
31.3 The encoding prefixed type . 55
32 Notation for the object identifier type . 56
33 Notation for the relative object identifier type . 58
34 Notation for the OID internationalized resource identifier type . 59
35 Notation for the relative OID internationalized resource identifier type . 60
36 Notation for the embedded-pdv type . 60
37 Notation for the external type . 62
iv Rec. ITU-T X.680 (02/2021)
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ISO/IEC 8824-1:2021(E)
38 The time type . 63
38.1 General . 63
38.2 Time properties and settings of time abstract values . 63
38.3 Basic value notation and XML value notation for time abstract values with specified property
settings . 67
38.4 Useful time types . 71
39 The character string types . 72
40 Notation for character string types . 73
41 Definition of restricted character string types . 73
42 Naming characters, collections and property category sets . 77
43 Canonical order of characters . 81
44 Definition of unrestricted character string types . 82
45 Notation for types defined in clauses 46 to 48 . 83
46 Generalized time . 83
47 Universal time . 84
48 The object descriptor type . 85
49 Constrained types . 86
50 Element set specification . 87
51 Subtype elements . 89
51.1 General . 89
51.2 Single value . 90
51.3 Contained subtype . 90
51.4 Value range . 90
51.5 Size constraint . 91
51.6 Type constraint . 91
51.7 Permitted alphabet . 91
51.8 Inner subtyping. 92
51.9 Pattern constraint . 93
51.10 Property settings . 93
51.11 Duration range . 94
51.12 Time point range . 95
51.13 Recurrence range . 95
52 The extension marker . 95
53 The exception identifier . 97
54 Encoding control sections . 98
A.1 Definition . 99
A.2 Metacharacters . 99
B.1 General . 103
B.2 The ASN.1 defined time types module . 103
C.1 The need for the value mapping concept (tutorial introduction) . 108
C.2 Value mappings . 110
C.3 Identical type definitions . 111
C.4 Specification of value mappings . 113
C.5 Additional value mappings defined for the character string types . 113
C.6 Specific type and value compatibility requirements . 114
C.7 Examples . 115
C.7.2 Example 1 . 115
C.7.3 Example 2 . 115
C.7.4 Example 3 . 115
C.7.5 Example 4 . 115
C.7.6 Example 5 . 115
C.7.7 Example 6 . 116
Rec. ITU-T X.680 (02/2021) v
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ISO/IEC 8824-1:2021(E)
D.1 Values assigned in this Recommendation | International Standard . 117
D.2 Object identifiers in the ASN.1 and encoding rules standards . 117
F.1 General . 120
F.2 Use of the International Object Identifier tree by the object identifier (OBJECT IDENTIFIER)
type . 120
F.3 Use of the International Object Identifier tree by the OID internationalized resource identifier
(OID-IRI) type . 120
G.1 Example of a personnel record . 121
G.1.1 Informal description of Personnel Record . 121
G.1.2 ASN.1 description of the record structure . 121
G.1.3 ASN.1 description of a record value . 122
G.2 Guidelines for use of the notation . 122
G.2.1 Boolean . 123
G
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