ISO/IEC 8825-4:2008
Information technology — ASN.1 encoding rules: XML Encoding Rules (XER) — Part 4:
ISO/IEC 8825-4:2008 specifies a set of basic XML Encoding Rules (BASIC-XER) that can be used to derive a transfer syntax for values of types defined in ISO/IEC 8824-1 and ISO/IEC 8824-2. It 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. ISO/IEC 8825-4:2008 further specifies a set of extended XML Encoding Rules (EXTENDED-XER) which adds further encoder 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 ISO/IEC 8825-4:2008:
- 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 ISO/IEC 8824-1.
ISO/IEC 8825-4:2008 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.
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CONTENTS
FOREWORD
Introduction
1 Scope
2 Normative references
2.1 Identical Recommendations | International Standards
2.2 Additional references
3 Definitions
3.1 ASN.1 Basic Encoding Rules (BER)
3.2 Additional definitions
4 Abbreviations
5 Encodings specified by this Recommendation | International Standard
6 Encoding instructions specified by this Recommendation | International Standard
7 Conformance
8 Basic XML encoding rules
8.1 Production of a complete BASIC-XER encoding
8.2 The XML prolog
8.3 The XML document element
8.4 Encoding of the EXTERNAL type
8.5 Encoding of the open type
8.6 Decoding of types with extension markers
9 Canonical XML encoding rules
9.1 General rules for canonical XER
9.2 Real values
9.3 Bitstring value
9.4 Octetstring value
9.5 Sequence value
9.6 Set value
9.7 Set-of value
9.8 Object identifier value
9.9 Relative object identifier value
9.10 GeneralizedTime
9.11 UTCTime
9.12 Open type value
9.13 The
type and the useful time types
10 Extended XML encoding rules
10.1 General
10.2 EXTENDED-XER conformance
10.3 Structure of an EXTENDED-XER encoding
11 Notation, character set and lexical items used in XER encoding instructions
12 Keywords
13 Assigning an XER encoding instruction to an ASN.1 type using a type prefix
14 Assigning an XER encoding instruction using an XER encoding control section
14.1 The encoding instruction assignment list
14.2 Identification of the targets for an XER encoding instruction using a target list
15 Multiple assignment of XER encoding instructions
15.1 Order in which multiple assignments are considered
15.2 Effect of assigning a negating encoding instruction
15.3 Multiple assignment of encoding instructions with multiple categories
15.4 Multiple assignment of XER encoding instructions of the same category
15.5 Permitted combinations of final encoding instructions
16 XER encoding instruction support for XML namespaces and qualified names
17 Specification of EXTENDED-XER encodings
17.1 The XML document element
17.2 The "TypeNameOrModifiedTypeName" production
17.3 The "AttributeList" production
17.4 The "ExtendedXMLValue" production
17.5 The "ExtendedXMLChoiceValue" production
17.6 The "ExtendedXMLSequenceValue" and "ExtendedXMLSetValue" productions
17.7 The "ExtendedXMLSequenceOfValue" and "ExtendedXMLSetOfValue" productions
17.8 The "ModifiedXMLIntegerValue" production
17.9 The "ModifiedXMLRealValue" production
18 The ANY-ATTRIBUTES encoding instruction
18.1 General
18.2 Restrictions
18.3 Effect on encodings
19 The ANY-ELEMENT encoding instruction
19.1 General
19.2 Restrictions
19.3 Effect on encodings
20 The ATTRIBUTE encoding instruction
20.1 General
20.2 Restrictions
20.3 Effect on encodings
21 The BASE64 encoding instruction
21.1 General
21.2 Restrictions
21.3 Effect on encodings
22 The DECIMAL encoding instruction
22.1 General
22.2 Restrictions
22.3 Effect on encodings
23 The DEFAULT-FOR-EMPTY encoding instruction
23.1 General
23.2 Restrictions
23.3 Effect on encodings
24 The ELEMENT encoding instruction
24.1 General
24.2 Restrictions
24.3 Effect on encodings
25 The EMBED-VALUES encoding instruction
25.1 General
25.2 Restrictions
25.3 Effect on encodings
26 The GLOBAL-DEFAULTS encoding instruction
26.1 General
26.2 Restrictions
26.3 Effect on encodings
27 The LIST encoding instruction
27.1 General
27.2 Restrictions
27.3 Effect on encodings
28 The NAME encoding instruction
28.1 General
28.2 Restrictions
28.3 Effect on encodings
29 The NAMESPACE encoding instruction
29.1 General
29.2 Restrictions
29.3 Effect on encodings
30 The PI-OR-COMMENT encoding instruction
30.1 General
30.2 Restrictions
30.3 Effect on the encodings
31 The TEXT encoding instruction
31.1 General
31.2 Restrictions
31.3 Effect on encodings
32 The UNTAGGED encoding instruction
32.1 General
32.2 Restrictions
32.3 Effect on encodings
33 The USE-NIL encoding instruction
33.1 General
33.2 Restrictions
33.3 Effect on encodings
34 The USE-NUMBER encoding instruction
34.1 General
34.2 Restrictions
34.3 Effect on encodings
35 The USE-ORDER encoding instruction
35.1 General
35.2 Restrictions
35.3 Effect on encodings
36 The USE-QNAME encoding instruction
36.1 General
36.2 Restrictions
36.3 Effect on encodings
37 The USE-TYPE encoding instruction
37.1 General
37.2 Restrictions
37.3 Effect on encodings
38 The USE-UNION encoding instruction
38.1 General
38.2 Restrictions
38.3 Effect on encodings
39 The WHITESPACE encoding instruction
39.1 General
39.2 Restrictions
39.3 Effect on encodings
40 Identification of the encoding rules
Annex A
Examples of BASIC-XER and CXER encodings
A.1 ASN.1 description of the record structure
A.2 ASN.1 description of a record value
A.3 Basic XML representation of this record value
A.4 Canonical XML representation of this record value
Annex B
Partial XML content and deterministic encodings
B.1 Partial XML content
B.2 Recommended restrictions on encodings producing partial XML element content
Annex C
Examples of EXTENDED-XER encodings using XER encoding instructions
C.1 Introduction
C.2 Simple examples
C.3 More complex examples
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CONTENTS
FOREWORD
Introduction
1 Scope
2 Normative references
2.1 Identical Recommendations | International Standards
2.2 Additional references
3 Definitions
3.1 ASN.1 Basic Encoding Rules (BER)
3.2 Additional definitions
4 Abbreviations
5 Encodings specified by this Recommendation | International Standard
6 Encoding instructions specified by this Recommendation | International Standard
7 Conformance
8 Basic XML encoding rules
8.1 Production of a complete BASIC-XER encoding
8.2 The XML prolog
8.3 The XML document element
8.4 Encoding of the EXTERNAL type
8.5 Encoding of the open type
8.6 Decoding of types with extension markers
9 Canonical XML encoding rules
9.1 General rules for canonical XER
9.2 Real values
9.3 Bitstring value
9.4 Octetstring value
9.5 Sequence value
9.6 Set value
9.7 Set-of value
9.8 Object identifier value
9.9 Relative object identifier value
9.10 GeneralizedTime
9.11 UTCTime
9.12 Open type value
9.13 The
type and the useful time types
10 Extended XML encoding rules
10.1 General
10.2 EXTENDED-XER conformance
10.3 Structure of an EXTENDED-XER encoding
11 Notation, character set and lexical items used in XER encoding instructions
12 Keywords
13 Assigning an XER encoding instruction to an ASN.1 type using a type prefix
14 Assigning an XER encoding instruction using an XER encoding control section
14.1 The encoding instruction assignment list
14.2 Identification of the targets for an XER encoding instruction using a target list
15 Multiple assignment of XER encoding instructions
15.1 Order in which multiple assignments are considered
15.2 Effect of assigning a negating encoding instruction
15.3 Multiple assignment of encoding instructions with multiple categories
15.4 Multiple assignment of XER encoding instructions of the same category
15.5 Permitted combinations of final encoding instructions
16 XER encoding instruction support for XML namespaces and qualified names
17 Specification of EXTENDED-XER encodings
17.1 The XML document element
17.2 The "TypeNameOrModifiedTypeName" production
17.3 The "AttributeList" production
17.4 The "ExtendedXMLValue" production
17.5 The "ExtendedXMLChoiceValue" production
17.6 The "ExtendedXMLSequenceValue" and "ExtendedXMLSetValue" productions
17.7 The "ExtendedXMLSequenceOfValue" and "ExtendedXMLSetOfValue" productions
17.8 The "ModifiedXMLIntegerValue" production
17.9 The "ModifiedXMLRealValue" production
18 The ANY-ATTRIBUTES encoding instruction
18.1 General
18.2 Restrictions
18.3 Effect on encodings
19 The ANY-ELEMENT encoding instruction
19.1 General
19.2 Restrictions
19.3 Effect on encodings
20 The ATTRIBUTE encoding instruction
20.1 General
20.2 Restrictions
20.3 Effect on encodings
21 The BASE64 encoding instruction
21.1 General
21.2 Restrictions
21.3 Effect on encodings
22 The DECIMAL encoding instruction
22.1 General
22.2 Restrictions
22.3 Effect on encodings
23 The DEFAULT-FOR-EMPTY encoding instruction
23.1 General
23.2 Restrictions
23.3 Effect on encodings
24 The ELEMENT encoding instruction
24.1 General
24.2 Restrictions
24.3 Effect on encodings
25 The EMBED-VALUES encoding instruction
25.1 General
25.2 Restrictions
25.3 Effect on encodings
26 The GLOBAL-DEFAULTS encoding instruction
26.1 General
26.2 Restrictions
26.3 Effect on encodings
27 The LIST encoding instruction
27.1 General
27.2 Restrictions
27.3 Effect on encodings
28 The NAME encoding instruction
28.1 General
28.2 Restrictions
28.3 Effect on encodings
29 The NAMESPACE encoding instruction
29.1 General
29.2 Restrictions
29.3 Effect on encodings
30 The PI-OR-COMMENT encoding instruction
30.1 General
30.2 Restrictions
30.3 Effect on the encodings
31 The TEXT encoding instruction
31.1 General
31.2 Restrictions
31.3 Effect on encodings
32 The UNTAGGED encoding instruction
32.1 General
32.2 Restrictions
32.3 Effect on encodings
33 The USE-NIL encoding instruction
33.1 General
33.2 Restrictions
33.3 Effect on encodings
34 The USE-NUMBER encoding instruction
34.1 General
34.2 Restrictions
34.3 Effect on encodings
35 The USE-ORDER encoding instruction
35.1 General
35.2 Restrictions
35.3 Effect on encodings
36 The USE-QNAME encoding instruction
36.1 General
36.2 Restrictions
36.3 Effect on encodings
37 The USE-TYPE encoding instruction
37.1 General
37.2 Restrictions
37.3 Effect on encodings
38 The USE-UNION encoding instruction
38.1 General
38.2 Restrictions
38.3 Effect on encodings
39 The WHITESPACE encoding instruction
39.1 General
39.2 Restrictions
39.3 Effect on encodings
40 Identification of the encoding rules
Annex A
Examples of BASIC-XER and CXER encodings
A.1 ASN.1 description of the record structure
A.2 ASN.1 description of a record value
A.3 Basic XML representation of this record value
A.4 Canonical XML representation of this record value
Annex B
Partial XML content and deterministic encodings
B.1 Partial XML content
B.2 Recommended restrictions on encodings producing partial XML element content
Annex C
Examples of EXTENDED-XER encodings using XER encoding instructions
C.1 Introduction
C.2 Simple examples
C.3 More complex examples