ISO/IEC 8825-4:2015

Information technology — ASN.1 encoding rules: XML Encoding Rules (XER) — Part 4:

ISO/IEC 8825-4:2015 specifies a set of basic XML Encoding Rules (BASIC-XER) that may be used to derive a transfer syntax for values of types defined in Rec. ITU-T X.680 | ISO/IEC 8824-1 and Rec. ITU-T X.681 | ISO/IEC 8824-2. This Recommendation | International Standard also specifies a set of Canonical XML Encoding Rules (CXER) which provide constraints on the basic XML Encoding Rules and produce a unique encoding for any given ASN.1 value. This Recommendation | International Standard further specifies a set of extended XML Encoding Rules (EXTENDED-XER) which adds further encoders options, and also allows the ASN.1 specifier to vary the encoding that would be produced by BASIC-XER. It is implicit in the specification of these encoding rules that they are also used for decoding. The encoding rules specified in this Recommendation | International Standard: - are used at the time of communication; - are intended for use in circumstances where displaying of values and/or processing them using commonly available XML tools (such as browsers) is the major concern in the choice of encoding rules; - allow the extension of an abstract syntax by addition of extra values for all forms of extensibility described in Rec. ITU-T X.680 | ISO/IEC 8824‑1. ISO/IEC 8825-4:2015 also specifies the syntax and semantics of XER encoding instructions, and the rules for their assignment and combination. XER encoding instructions can be used to control the EXTENDED-XER encoding for specific ASN.1 types.

Technologies de l'information — Règles de codage ASN.1: Règles de codage XML (XER) — Partie 4:

General Information

• Status: Withdrawn
• Publication Date: 11-Nov-2015
• Withdrawal Date: 11-Nov-2015
• ICS: 35.100.60 - Presentation layer
• Technical Committee: ISO/IEC JTC 1/SC 6 - Telecommunications and information exchange between systems
• Drafting Committee: ISO/IEC JTC 1/SC 6/WG 7 - Network, transport and future network
• Current Stage: 9599 - Withdrawal of International Standard
• Completion Date: 30-Jun-2021

Relations

• Revised: ISO/IEC 8825-4:2021 - Information technology — ASN.1 encoding rules — Part 4: XML Encoding Rules (XER)
• Effective Date: 15-Aug-2020
• Revises: ISO/IEC 8825-4:2008 - Information technology — ASN.1 encoding rules: XML Encoding Rules (XER) — Part 4:
• Effective Date: 05-Nov-2015

Standards Content (Sample)

INTERNATIONAL ISO/IEC
STANDARD 8825-4
Third edition
2015-11-15

Information technology — ASN.1
encoding rules: XML Encoding Rules
(XER)
Technologies de l'information — Règles de codage ASN.1: Règles de
codage XML (XER)






Reference number
ISO/IEC 8825-4:2015(E)
©
ISO/IEC 2015

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ISO/IEC 8825-4:2015(E)
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©  ISO/IEC 2015
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ii © ISO/IEC 2015 – All rights reserved

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ISO/IEC 8825-4:2015(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 members of
ISO or IEC participate in the development of International Standards through technical committees
established by the respective organization to deal with particular fields of technical activity. ISO and IEC
technical committees collaborate in fields of mutual interest. Other international organizations, governmental
and non-governmental, in liaison with ISO and IEC, also take part in the work. In the field of information
technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of the joint technical committee is to prepare International Standards. Draft International
Standards adopted by the joint technical committee are circulated to national bodies for voting. Publication as
an International Standard requires approval by at least 75 % of the national bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights.
This third edition cancels and replaces the second edition of ISO/IEC 8825-4:2008 which has been technically
revised. It also incorporates ISO/IEC 8825-4:2008/Cor.1:2012 and ISO/IEC 8825-4:2008/Cor.2:2014.
ISO/IEC 8825-4 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.693 (08/2015).
© ISO/IEC 2015 – All rights reserved iii

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Int e rnat ional Telecommunicat ion U n ion


ITU-T X.693
(08/2015)
TELECOMMUNICATION
STANDARDIZATION SECTOR
OF ITU

SERIES X: DATA NETWORKS, OPEN SYSTEM
COMMUNICATIONS AND SECURITY
OSI networking and system aspects – Abstract Syntax
Notation One (ASN.1)


Information technology – ASN.1 encoding rules:
XML Encoding Rules (XER)

Recommendation ITU-T X.693

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ITU-T X-SERIES RECOMMENDATIONS
DATA NETWORKS, OPEN SYSTEM COMMUNICATIONS AND SECURITY

PUBLIC DATA NETWORKS
Services and facilities X.1–X.19
Interfaces X.20–X.49
Transmission, signalling and switching X.50–X.89
Network aspects X.90–X.149
Maintenance X.150–X.179
Administrative arrangements X.180–X.199
OPEN SYSTEMS INTERCONNECTION
Model and notation X.200–X.209
Service definitions X.210–X.219
Connection-mode protocol specifications X.220–X.229
Connectionless-mode protocol specifications X.230–X.239
PICS proformas X.240–X.259
Protocol Identification X.260–X.269
Security Protocols X.270–X.279
Layer Managed Objects X.280–X.289
Conformance testing X.290–X.299
INTERWORKING BETWEEN NETWORKS
General X.300–X.349
Satellite data transmission systems X.350–X.369
IP-based networks X.370–X.379
MESSAGE HANDLING SYSTEMS X.400–X.499
DIRECTORY X.500–X.599
OSI NETWORKING AND SYSTEM ASPECTS
Networking X.600–X.629
Efficiency X.630–X.639
Quality of service X.640–X.649
Naming, Addressing and Registration X.650–X.679
Abstract Syntax Notation One (ASN.1) X.680–X.699
OSI MANAGEMENT
Systems management framework and architecture X.700–X.709
Management communication service and protocol X.710–X.719
Structure of management information X.720–X.729
Management functions and ODMA functions X.730–X.799
SECURITY X.800–X.849
OSI APPLICATIONS
Commitment, concurrency and recovery X.850–X.859
Transaction processing X.860–X.879
Remote operations X.880–X.889
Generic applications of ASN.1 X.890–X.899
OPEN DISTRIBUTED PROCESSING X.900–X.999
INFORMATION AND NETWORK SECURITY X.1000–X.1099
SECURE APPLICATIONS AND SERVICES X.1100–X.1199
CYBERSPACE SECURITY X.1200–X.1299
SECURE APPLICATIONS AND SERVICES X.1300–X.1399
CYBERSECURITY INFORMATION EXCHANGE X.1500–X.1599
CLOUD COMPUTING SECURITY X.1600–X.1699

For further details, please refer to the list of ITU-T Recommendations.

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INTERNATIONAL STANDARD ISO/IEC 8825-4
RECOMMENDATION ITU-T X.693
Information technology – ASN.1 encoding rules:
XML Encoding Rules (XER)



Summary
Recommendation ITU-T X.693 | ISO/IEC 8825-4 specifies rules for encoding values of ASN.1 types using the Extensible
Markup Language (XML).


History
*
Edition Recommendation Approval Study Group Unique ID
1.0 ITU-T X.693 2001-12-22 7 11.1002/1000/5565
1.1 ITU-T X.693 (2001) Amd. 1 2003-10-29 17 11.1002/1000/7023
1.2 ITU-T X.693 (2001) Amd. 2 2006-06-13 17 11.1002/1000/8841
1.3 ITU-T X.693 (2001) Amd. 3 2007-05-29 17 11.1002/1000/9110
2.0 ITU-T X.693 2008-11-13 17 11.1002/1000/9611
2.1 ITU-T X.693 (2008) Cor. 1 2011-10-14 17 11.1002/1000/11381
2.2 ITU-T X.693 (2008) Cor. 2 2014-03-01 17 11.1002/1000/12148
3.0 ITU-T X.693 2015-08-13 17 11.1002/1000/12489





BBBBBBBBBBBBBBBB
*
To access the Recommendation, type the URL http://handle.itu.int/ in the address field of your web browser, followed by the
Recommendation's unique ID. For example, http://handle.itu.int/11.1002/1000/11830-en.
  Rec. ITU-T X.693 (08/2015) i

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FOREWORD
The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of
telecommunications, information and communication technologies (ICTs). The ITU Telecommunication
Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical,
operating and tariff questions and issuing Recommendations on them with a view to standardizing
telecommunications on a worldwide basis.
The World Telecommunication Standardization Assembly (WTSA), which meets every four years,
establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on
these topics.
The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1.
In some areas of information technology which fall within ITU-T's purview, the necessary standards are
prepared on a collaborative basis with ISO and IEC.



NOTE
In this Recommendation, the expression "Administration" is used for conciseness to indicate both a
telecommunication administration and a recognized operating agency.
Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain
mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the
Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some
other obligatory language such as "must" and the negative equivalents are used to express requirements. The
use of such words does not suggest that compliance with the Recommendation is required of any party.




INTELLECTUAL PROPERTY RIGHTS
ITU draws attention to the possibility that the practice or implementation of this Recommendation may
involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence,
validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others
outside of the Recommendation development process.
As of the date of approval of this Recommendation, ITU had not received notice of intellectual property,
protected by patents, which may be required to implement this Recommendation. However, implementers
are cautioned that this may not represent the latest information and are therefore strongly urged to consult
the TSB patent database at http://www.itu.int/ITU-T/ipr/.



¤ ITU 2015
All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the
prior written permission of ITU.
ii Rec. ITU-T X.693 (08/2015)

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CONTENTS
Page
1 SCOPE . 1
2 NORMATIVE REFERENCES . 1
2.1 IDENTICAL RECOMMENDATIONS | INTERNATIONAL STANDARDS . 1
2.2 ADDITIONAL REFERENCES . 2
3 DEFINITIONS . 2
3.1 ASN.1 BASIC ENCODING RULES (BER) . 2
3.2 ADDITIONAL DEFINITIONS . 2
4 ABBREVIATIONS . 4
5 ENCODINGS SPECIFIED BY THIS RECOMMENDATION | INTERNATIONAL STANDARD. 4
6 ENCODING INSTRUCTIONS SPECIFIED BY THIS RECOMMENDATION | INTERNATIONAL
STANDARD . 5
7 CONFORMANCE . 5
8 BASIC XML ENCODING RULES . 5
8.1 PRODUCTION OF A COMPLETE BASIC-XER ENCODING . 5
8.2 THE XML PROLOG . 6
8.3 THE XML DOCUMENT ELEMENT . 6
8.4 ENCODING OF THE EXTERNAL TYPE . 7
8.5 ENCODING OF THE OPEN TYPE . 7
8.6 DECODING OF TYPES WITH EXTENSION MARKERS . 7
9 CANONICAL XML ENCODING RULES . 7
9.1 GENERAL RULES FOR CANONICAL XER . 7
9.2 REAL VALUES . 8
9.3 BITSTRING VALUE . 8
9.4 OCTETSTRING VALUE . 8
9.5 SEQUENCE VALUE . 8
9.6 SET VALUE . 8
9.7 SET-OF VALUE . 9
9.8 OBJECT IDENTIFIER VALUE . 9
9.9 RELATIVE OBJECT IDENTIFIER VALUE . 9
9.10 GENERALIZEDTIME . 9
9.11 UTCTIME . 9
9.12 OPEN TYPE VALUE . 10
9.13 THE TIME TYPE AND THE USEFUL TIME TYPES . 10
10 EXTENDED XML ENCODING RULES . 10
10.1 GENERAL . 10
10.2 EXTENDED-XER CONFORMANCE . 11
10.3 STRUCTURE OF AN EXTENDED-XER ENCODING . 13
11 NOTATION, CHARACTER SET AND LEXICAL ITEMS USED IN XER ENCODING
INSTRUCTIONS . 14
  Rec. ITU-T X.693 (08/2015) iii

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12 KEYWORDS . 14
13 ASSIGNING AN XER ENCODING INSTRUCTION TO AN ASN.1 TYPE USING A TYPE
PREFIX . 15
14 ASSIGNING AN XER ENCODING INSTRUCTION USING AN XER ENCODING CONTROL
SECTION . 18
14.1 THE ENCODING INSTRUCTION ASSIGNMENT LIST . 18
14.2 IDENTIFICATION OF THE TARGETS FOR AN XER ENCODING INSTRUCTION USING
A TARGET LIST . 18
14.2.1 GENERAL RULES . 18
14.2.2 TARGET IDENTIFICATION USING AN ASN.1 TYPE REFERENCE AND
IDENTIFIERS . 21
14.2.3 TARGET IDENTIFICATION USING A BUILT-IN TYPE NAME . 22
14.2.4 USE OF IDENTIFIERS IN CONTEXT. 23
14.2.5 USE OF IMPORTED TYPES IDENTIFICATION . 24
15 MULTIPLE ASSIGNMENT OF XER ENCODING INSTRUCTIONS . 24
15.1 ORDER IN WHICH MULTIPLE ASSIGNMENTS ARE CONSIDERED . 24
15.2 EFFECT OF ASSIGNING A NEGATING ENCODING INSTRUCTION . 25
15.3 MULTIPLE ASSIGNMENT OF ENCODING INSTRUCTIONS WITH MULTIPLE
CATEGORIES . 25
15.4 MULTIPLE ASSIGNMENT OF XER ENCODING INSTRUCTIONS OF THE SAME
CATEGORY . 25
15.5 PERMITTED COMBINATIONS OF FINAL ENCODING INSTRUCTIONS . 26
16 XER ENCODING INSTRUCTION SUPPORT FOR XML NAMESPACES AND QUALIFIED
NAMES . 27
17 SPECIFICATION OF EXTENDED-XER ENCODINGS . 28
17.1 THE XML DOCUMENT ELEMENT . 29
17.2 THE "TYPENAMEORMODIFIEDTYPENAME" PRODUCTION . 29
17.3 THE "ATTRIBUTELIST" PRODUCTION . 29
17.4 THE "EXTENDEDXMLVALUE" PRODUCTION. 29
17.5 THE "EXTENDEDXMLCHOICEVALUE" PRODUCTION . 31
17.6 THE "EXTENDEDXMLSEQUENCEVALUE" AND "EXTENDEDXMLSETVALUE"
PRODUCTIONS . 31
17.7 THE "EXTENDEDXMLSEQUENCEOFVALUE" AND "EXTENDEDXMLSETOFVALUE"
PRODUCTIONS . 32
17.8 THE "MODIFIEDXMLINTEGERVALUE" PRODUCTION . 33
17.9 THE "MODIFIEDXMLREALVALUE" PRODUCTION . 34
18 THE ANY-ATTRIBUTES ENCODING INSTRUCTION . 34
18.1 GENERAL . 34
18.2 RESTRICTIONS . 35
18.3 EFFECT ON ENCODINGS . 36
19 THE ANY-ELEMENT ENCODING INSTRUCTION . 36
19.1 GENERAL . 36
19.2 RESTRICTIONS . 36
19.3 EFFECT ON ENCODINGS . 37
20 THE ATTRIBUTE ENCODING INSTRUCTION . 38
20.1 GENERAL . 38
iv Rec. ITU-T X.693 (08/2015)

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20.2 RESTRICTIONS . 38
20.3 EFFECT ON ENCODINGS . 38
21 THE BASE64 ENCODING INSTRUCTION . 40
21.1 GENERAL . 40
21.2 RESTRICTIONS . 40
21.3 EFFECT ON ENCODINGS . 40
22 THE DECIMAL ENCODING INSTRUCTION . 41
22.1 GENERAL . 41
22.2 RESTRICTIONS . 41
22.3 EFFECT ON ENCODINGS . 42
23 THE DEFAULT-FOR-EMPTY ENCODING INSTRUCTION . 42
23.1 GENERAL . 42
23.2 RESTRICTIONS . 43
23.3 EFFECT ON ENCODINGS . 44
24 THE ELEMENT ENCODING INSTRUCTION . 44
24.1 GENERAL . 44
24.2 RESTRICTIONS . 44
24.3 EFFECT ON ENCODINGS . 44
25 THE EMBED-VALUES ENCODING INSTRUCTION . 44
25.1 GENERAL . 44
25.2 RESTRICTIONS . 45
25.3 EFFECT ON ENCODINGS . 45
26 THE GLOBAL-DEFAULTS ENCODING INSTRUCTION . 46
26.1 GENERAL . 46
26.2 RESTRICTIONS . 46
26.3 EFFECT ON ENCODINGS . 46
27 THE LIST ENCODING INSTRUCTION . 47
27.1 GENERAL . 47
27.2 RESTRICTIONS . 47
27.3 EFFECT ON ENCODINGS . 47
28 THE NAME ENCODING INSTRUCTION . 48
28.1 GENERAL . 48
28.2 RESTRICTIONS . 49
28.3 EFFECT ON ENCODINGS . 49
29 THE NAMESPACE ENCODING INSTRUCTION . 50
29.1 GENERAL . 50
29.2 RESTRICTIONS . 50
29.3 EFFECT ON ENCODINGS . 51
30 THE PI-OR-COMMENT ENCODING INSTRUCTION . 51
30.1 GENERAL . 51
30.2 RESTRICTIONS . 52
30.3 EFFECT ON THE ENCODINGS . 52
31 THE TEXT ENCODING INSTRUCTION . 52
  Rec. ITU-T X.693 (08/2015) v

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31.1 GENERAL . 52
31.2 RESTRICTIONS . 53
31.3 EFFECT ON ENCODINGS . 53
32 THE UNTAGGED ENCODING INSTRUCTION . 54
32.1 GENERAL . 54
32.2 RESTRICTIONS . 55
32.3 EFFECT ON ENCODINGS . 55
33 THE USE-NIL ENCODING INSTRUCTION . 56
33.1 GENERAL . 56
33.2 RESTRICTIONS . 56
33.3 EFFECT ON ENCODINGS . 57
34 THE USE-NUMBER ENCODING INSTRUCTION . 57
34.1 GENERAL . 57
34.2 RESTRICTIONS . 57
34.3 EFFECT ON ENCODINGS . 57
35 THE USE-ORDER ENCODING INSTRUCTION . 58
35.1 GENERAL . 58
35.2 RESTRICTIONS . 58
35.3 EFFECT ON ENCODINGS . 59
36 THE USE-QNAME ENCODING INSTRUCTION . 59
36.1 GENERAL . 59
36.2 RESTRICTIONS . 59
36.3 EFFECT ON ENCODINGS . 60
37 THE USE-TYPE ENCODING INSTRUCTION . 60
37.1 GENERAL . 60
37.2 RESTRICTIONS . 60
37.3 EFFECT ON ENCODINGS . 61
38 THE USE-UNION ENCODING INSTRUCTION . 61
38.1 GENERAL . 61
38.2 RESTRICTIONS .
...