1、 I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n ITU-T X.693 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (08/2015) SERIES X: DATA NETWORKS, OPEN SYSTEM COMMUNICATIONS AND SECURITY OSI networking and system aspects Abstract Syntax Notation One (ASN.1) Information technology
2、ASN.1 encoding rules: XML Encoding Rules (XER) Recommendation ITU-T X.693 ITU-T X-SERIES RECOMMENDATIONS DATA NETWORKS, OPEN SYSTEM COMMUNICATIONS AND SECURITY PUBLIC DATA NETWORKS Services and facilities X.1X.19 Interfaces X.20X.49 Transmission, signalling and switching X.50X.89 Network aspects X.9
3、0X.149 Maintenance X.150X.179 Administrative arrangements X.180X.199 OPEN SYSTEMS INTERCONNECTION Model and notation X.200X.209 Service definitions X.210X.219 Connection-mode protocol specifications X.220X.229 Connectionless-mode protocol specifications X.230X.239 PICS proformas X.240X.259 Protocol
4、Identification X.260X.269 Security Protocols X.270X.279 Layer Managed Objects X.280X.289 Conformance testing X.290X.299 INTERWORKING BETWEEN NETWORKS General X.300X.349 Satellite data transmission systems X.350X.369 IP-based networks X.370X.379 MESSAGE HANDLING SYSTEMS X.400X.499 DIRECTORY X.500X.59
5、9 OSI NETWORKING AND SYSTEM ASPECTS Networking X.600X.629 Efficiency X.630X.639 Quality of service X.640X.649 Naming, Addressing and Registration X.650X.679 Abstract Syntax Notation One (ASN.1) X.680X.699 OSI MANAGEMENT Systems management framework and architecture X.700X.709 Management communicatio
6、n service and protocol X.710X.719 Structure of management information X.720X.729 Management functions and ODMA functions X.730X.799 SECURITY X.800X.849 OSI APPLICATIONS Commitment, concurrency and recovery X.850X.859 Transaction processing X.860X.879 Remote operations X.880X.889 Generic applications
7、 of ASN.1 X.890X.899 OPEN DISTRIBUTED PROCESSING X.900X.999 INFORMATION AND NETWORK SECURITY X.1000X.1099 SECURE APPLICATIONS AND SERVICES X.1100X.1199 CYBERSPACE SECURITY X.1200X.1299 SECURE APPLICATIONS AND SERVICES X.1300X.1399 CYBERSECURITY INFORMATION EXCHANGE X.1500X.1599 CLOUD COMPUTING SECUR
8、ITY X.1600X.1699 For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T X.693 (08/2015) i 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 88
9、25-4 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.
10、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、11.1002/1000/12489 * To access the Recommendation, type the URL http:/handle.itu.int/ in the address field of your web browser, followed by the Recommendations unique ID. For example, http:/handle.itu.int/11.1002/1000/11830-en. ii Rec. ITU-T X.693 (08/2015) FOREWORD The International Telecommunicati
12、on 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 quest
13、ions 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
14、 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-Ts purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. NOTE In this Recommendation, t
15、he 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 a
16、pplicability) 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 wi
17、th the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTSITU 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 appli
18、cability 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 imple
19、ment 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 me
20、ans whatsoever, without the prior written permission of ITU. Rec. ITU-T X.693 (08/2015) iii 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
21、 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
22、 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
23、 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
24、 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 iv Rec. ITU-T X.693 (08/2015) 12 KEYWORDS 14 13 ASSIGNING AN XER ENCODING INSTRUCTION TO AN ASN.1 TYPE USING A TYPE PREFIX . 15 14 AS
25、SIGNING 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
26、 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 A
27、SSIGNING 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 SUPP
28、ORT 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“ PRO
29、DUCTION 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
30、 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 Rec. ITU-T X.693 (08/2015) v 20.2 RESTRICTIONS 38
31、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 GENER
32、AL 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
33、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 NAMESPA
34、CE 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 vi Rec. ITU-T X.693 (08/2015) 31.1 GENERAL 52 31.2
35、 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 . 5
36、7 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 ENC
37、ODING 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 61 38.3 EFFECT ON ENCODINGS 62 39 THE WHITESPACE ENCODING INSTRUCTION 63 39.1 GENERAL 63 39.2 RESTRICTIONS 63 39.3 EFFECT ON ENCODINGS 64
38、 40 IDENTIFICATION OF THE ENCODING RULES . 64 ANNEX A EXAMPLES OF BASIC-XER AND CXER ENCODINGS 65 A.1 ASN.1 DESCRIPTION OF THE RECORD STRUCTURE . 65 A.2 ASN.1 DESCRIPTION OF A RECORD VALUE 65 A.3 BASIC XML REPRESENTATION OF THIS RECORD VALUE 65 A.4 CANONICAL XML REPRESENTATION OF THIS RECORD VALUE .
39、 66 ANNEX B PARTIAL XML CONTENT AND DETERMINISTIC ENCODINGS . 67 B.1 PARTIAL XML CONTENT 67 Rec. ITU-T X.693 (08/2015) vii B.2 RECOMMENDED RESTRICTIONS ON ENCODINGS PRODUCING PARTIAL XML ELEMENT CONTENT 67 ANNEX C EXAMPLES OF EXTENDED-XER ENCODINGS USING XER ENCODING INSTRUCTIONS . 70 C.1 INTRODUCTI
40、ON 70 C.2 SIMPLE EXAMPLES. 70 C.2.1 A BASE-BALL CARD 70 C.2.2 AN EMPLOYEE 71 C.3 MORE COMPLEX EXAMPLES . 71 C.3.1 USING A UNION OF TWO SIMPLE TYPES 71 C.3.2 USING A TYPE IDENTIFICATION ATTRIBUTE . 72 C.3.3 USING ENUMERATION VALUES . 72 C.3.4 USING AN EMPTY ENCODING FOR A DEFAULT VALUE . 72 C.3.5 USI
41、NG EMBEDDED-VALUES FOR NOTIFICATION OF A PAYMENT DUE . 72 viii Rec. ITU-T X.693 (08/2015) 1 Introduction Rec. ITU-T X.680 | ISO/IEC 8824-1, Rec. ITU-T X.681 | ISO/IEC 8824-2, Rec. ITU-T X.682 | ISO/IEC 8824-3, Rec. ITU-T X.683 | ISO/IEC 8824-4 together describe Abstract Syntax Notation One (ASN.1),
42、a notation for the definition of messages to be exchanged between peer applications. This Recommendation | International Standard defines encoding rules that may be applied to values of ASN.1 types defined using the notation specified in Rec. ITU-T X.680 | ISO/IEC 8824-1 and Rec. ITU-T X.681 | ISO/I
43、EC 8824-2. Application of these encoding rules produces a transfer syntax for such values. It is implicit in the specification of these encoding rules that they are also to be used for decoding. There is more than one set of encoding rules that can be applied to values of ASN.1 types. This Recommend
44、ation | International Standard defines three sets of encoding rules that use the Extensible Markup Language (XML). These encoding rules all produce an XML document compliant to W3C XML 1.0. The first set is called the Basic XML Encoding Rules (BASIC-XER). The second set is called the Canonical XML E
45、ncoding Rules (CANONICAL-XER, or CXER) because there is only one way of encoding an ASN.1 value using these encoding rules. (Canonical encoding rules are generally used for applications using security-related features such as digital signatures.) The third set is called the extended XML Encoding Rul
46、es (EXTENDED-XER). The extended XML Encoding Rules allow additional encoders options, and take account of encoding instructions that specify variations of the BASIC-XER encodings in order to support specific styles of XML documents (see below). The extended XML Encoding Rules are not canonical, and
47、there is no canonical form for these rules defined in this Recommendation | International Standard. There are many aspects of an XML representation of data (such as the use of XML attributes instead of child elements, or the use of white-space delimited lists) whose use is a matter of style and XML
48、designer choice. If a type defined in an ASN.1 specification is encoded by BASIC-XER or by CXER, then there is a single fixed style used for the XML representation, with no user control of stylistic features. This Recommendation | International Standard specifies the syntax and semantics of XER enco
49、ding instructions which specify the stylistic features of the XML in an EXTENDED-XER encoding. XER encoding instructions can also be used to determine the possible insertion of XML processing instructions in an EXTENDED-XER encoding. XER encoding instructions are ignored by BASIC-XER and by CXER, but are used by EXTENDED-XER. NOTE “Stylistic features“, such as use of attributes or white-space delimited lis
