ISO/IEC 8825-8:2018

Information technology - ASN.1 encoding rules - Part 8: Specification of JavaScript Object Notation Encoding Rules (JER)

This Recommendation | International Standard specifies a set of JavaScript Object Notation Encoding Rules (JER) that may be used to derive a transfer syntax for values of types defined in 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. It is implicit in the specification of these encoding rules that they are also to be 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 interoperability with applications using JSON 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. This Recommendation | International Standard also specifies the syntax and semantics of JER encoding instructions, and the rules for their assignment and combination. JER encoding instructions can be used to control the JER encoding for specific ASN.1 types.

Technologies de l'information — Règles de codage ASN.1 — Partie 8: Titre manque

General Information

• Status: Withdrawn
• Publication Date: 11-Oct-2018
• Withdrawal Date: 11-Oct-2018
• 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 - Telecommunications and information exchange between systems
• Current Stage: 9599 - Withdrawal of International Standard
• Start Date: 30-Jun-2021
• Completion Date: 30-Oct-2025

Relations

• Revised: ISO/IEC 8825-8:2021 - Information technology - ASN.1 encoding rules - Part 8: Specification of JavaScript Object Notation Encoding Rules (JER)
• Effective Date: 12-Oct-2020

Standards Content (Sample)

INTERNATIONAL ISO/IEC
STANDARD 8825-8
First edition
2018-10
Information technology — ASN.1
encoding rules —
Part 8:
Specification of JavaScript Object
Notation Encoding Rules (JER)
Technologies de l'information — Règles de codage ASN.1 —
Reference number
©
ISO/IEC 2018
© ISO/IEC 2018
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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ii © ISO/IEC 2018 – All rights reserved

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.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of document should be noted. This document was drafted in accordance with the editorial
rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
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.
Details 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).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the World
Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT)
see www.iso.org/iso/foreword.html.
ISO/IEC 8825‐8 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.697 (10/2017).
A list of all parts in the ISO/IEC 8825 series can be found on the ISO website.
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.
iii-1
© ISO/IEC 2018 – All rights reserved

CONTENTS
Page
1 Scope . 1
2 Normative references . 1
2.1 Identical Recommendations | International Standards . 1
2.2 Additional references . 1
3 Definitions . 2
3.1 Specification of Basic Notation . 2
3.2 Information Object Specification . 2
3.3 Constraint Specification . 2
3.4 Parameterization of ASN.1 Specification . 2
3.5 Basic Encoding Rules (BER) . 2
3.6 Packed Encoding Rules (PER) . 2
3.7 Additional definitions . 2
4 Abbreviations . 3
5 Encodings specified by this Recommendation | International Standard . 3
6 Conformance . 4
7 General provisions . 4
7.1 Use of the type notation . 4
7.2 Constraints . 4
7.3 Type and value model used for encoding . 6
7.4 Types to be encoded . 6
7.5 Encoding instructions . 6
7.6 Production of a complete JER encoding . 7
8 Notation, lexical items and keywords used in JER encoding instructions . 7
9 Specifying JER encoding instructions . 8
10 Assigning a JER encoding instruction using a type prefix . 9
11 Assigning a JER encoding instruction using a JER encoding control section . 9
12 Identification of the targets for a JER encoding instruction . 9
12.1 General rules . 9
12.2 Types defined in the module . 10
12.3 Built-in types . 10
12.4 Types imported from another module . 10
13 Multiple assignment of JER encoding instructions . 10
13.1 Order in which multiple assignments are considered . 10
13.2 Effect of assigning a negating encoding instruction. 11
13.3 Multiple assignment of JER encoding instructions of the same category . 11
14 The ARRAY encoding instruction . 11
14.1 General . 11
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Rec. ITU-T X.697 (10/2017) iii

Page
14.2 Restrictions . 11
15 The BASE64 encoding instruction . 11
15.1 General . 11
15.2 Restrictions . 12
16 The NAME encoding instruction. 12
16.1 General . 12
16.2 Restrictions . 13
17 The OBJECT encoding instruction . 13
17.1 General . 13
17.2 Restrictions . 13
18 The TEXT encoding instruction. 13
18.1 General . 13
18.2 Restrictions . 14
19 The UNWRAPPED encoding instruction . 14
19.1 General . 14
19.2 Restrictions . 14
20 Encoding of boolean values . 14
21 Encoding of integer values . 15
22 Encoding of enumerated values . 15
23 Encoding of real values . 15
23.1 General . 15
23.2 Encoding of the special real values . 15
23.3 Encoding as a JSON number . 16
23.4 Encoding as a JSON object . 16
24 Encoding of bitstring values . 16
24.1 General . 16
24.2 Encoding of bitstring types with a fixed size . 16
24.3 Encoding of bitstring types with a variable size . 16
25 Encoding of octetstring values . 16
26 Encoding of the null value . 17
27 Encoding of sequence values . 17
27.1 General . 17
27.2 Array-based encoding . 17
27.3 Object-based encoding . 17
28 Encoding of sequence-of values . 17
29 Encoding of set values. 18
30 Encoding of set-of values . 18
© ISO/IEC 2018 – All rights reserved
iv Rec. ITU-T X.697 (10/2017)
Page
30.1 General . 18
30.2 Array-based encoding . 18
30.3 Object-based encoding . 18
31 Encoding of choice values . 18
31.1 General . 18
31.2 Unwrapped encoding . 18
31.3 Wrapped encoding . 18
32 Encoding of object identifier values . 19
33 Encoding of relative object identifier values . 19
34 Encoding of values of the internationalized resource reference type . 19
35 Encoding of values of the relative internationalized resource reference type . 19
36 Encoding of values of the embedded-pdv type . 19
37 Encoding of values of the external type . 19
38 Encoding of values of the restricted character string types . 19
39 Encoding of values of the unrestricted character string type . 20
40 Encoding of values of the time types . 20
41 Encoding of open type values . 20
Annex A – Examples of JER encodings . 21
A.1 ASN.1 description of the record structure . 21
A.2 ASN.1 description of a record value . 21
A.3 Example JER representation of this record value. 21
A.4 Additional examples of JER encodings . 22
Annex B – Examples of JER encoding instructions and their effect on the encodings . 25
B.1 ASN.1 description of the record structure . 25
B.2 ASN.1 description of a record value . 25
B.3 JER representation of this record value . 26
B.4 Additional examples of JER encodings . 26
B.5 Examples of JER encodings of choice types . 28
© ISO/IEC 2018 – All rights reserved
Rec. ITU-T X.697 (10/2017) v
Introduction
The publications 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), 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 the above-mentioned publications. 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 are more than one set of encoding rules that can be applied to values of ASN.1 types. This Recommendation |
International Standard defines a set of JavaScript Object Notation Encoding Rules (JER), so called because the
encodings they produce are instances of the JSON grammar specified in ECMA 404.
This Recommendation | International Standard specifies the syntax and semantics of JER encoding instructions which
modify the JSON text produced by the application of JER to certain ASN.1 types.
Clauses 8 to 12 list the JER encoding instructions and specify the syntax for their assignment to an ASN.1 type or
component using either a JER type prefix (see Rec. ITU-T X.680 | ISO/IEC 8824-1, clause 31.3) or a JER encoding
control section (see Rec. ITU-T X.680 | ISO/IEC 8824-1, clause 54).
Clause 13 defines the order of precedence if JER encoding instructions are present in both a JER type prefix and in a
JER encoding control section.
Clauses 14 to 19 specify:
a) the syntax of each JER encoding instruction used in a type prefix or a JER encoding control section;
b) restrictions on the JER encoding instructions that can be associated with a particular ASN.1 type
(resulting from inheritance and multiple assignments).
Clauses 20 to 41 specify the JER encoding of ASN.1 types, referencing earlier clauses which define the JER encoding
instructions.
Annex A is informative and contains examples of JER encodings where JER encoding instructions are not used.
Annex B is informative and contains examples of JER encoding instructions and their effect on the JER encodings.
© ISO/IEC 2018 – All rights reserved
vi Rec. ITU-T X.697 (10/2017)
INTERNATIONAL STANDARD
ITU-T RECOMMENDATION
Information technology – ASN.1 encoding rules: Specification of JavaScript
Object Notation Encoding Rules (JER)
1 Scope
This Recommendation | International Standard specifies a set of JavaScript Object Notation Encoding Rules (JER) that
may be used to derive a transfer syntax for values of types defined in 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. It is implicit in the
specification of these encoding rules that they are also to be 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 interoperability with applications using JSON 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.
This Recommendation | International Standard also specifies the syntax and semantics of JER encoding instructions,
and the rules for their assignment and combination. JER encoding instructions can be used to control the JER encoding
for specific ASN.1 types.
2 Normative references
The following Recommendations and International Standards contain provisions which, through reference in this text,
constitute provisions of this Recommendation | International Standard. At the time of publication, the editions indicated
were valid. All Recommendations and Standards are subject to revision, and parties to agreements based on this
Recommendation | International Standard are encouraged to investigate the possibility of applying the most recent
edition of the Recommendations and Standards listed below. Members of IEC and ISO maintain registers of currently
valid International Standards. The Telecommunication Standardization Bureau of the ITU maintains a list of currently
valid ITU-T Recommendations.
2.1 Identical Recommendations | International Standards
– Recommendation ITU-T X.680 (2015) | ISO/IEC 8824-1:2015, Information technology – Abstract
Syntax Notation One (ASN.1): Specification of basic notation.
– Recommendation ITU-T X.681 (2015) | ISO/IEC 8824-2:2015, Information technology – Abstract
Syntax Notation One (ASN.1): Information object specification.
– Recommendation ITU-T X.682 (2015) | ISO/IEC 8824-3:2015, Information technology – Abstract
Syntax Notation One (ASN.1): Constraint specification.
– Recommendation ITU-T X.683 (2015) | ISO/IEC 8824-4:2015, Information technology – Abstract
Syntax Notation One (ASN.1): Parameterization of ASN.1 specifications.
– Recommendation ITU-T X.690 (2015) | ISO/IEC 8825-1:2015, Information technology – ASN.1
encoding rules: Specification of Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and
Distinguished Encoding Rules (DER).
– Recommendation ITU-T X.691 (2015) | ISO/IEC 8825-2:2015, Information technology – ASN.1
encoding rules: Specification of Packed Encoding Rules (PER).
2.2 Additional references
– ECMA Standard ECMA-404 (2013) – The JSON Data Interchange Format.
– IETF RFC 2045 (1996), Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet
Message Bodies.
– ISO International Register of Coded Character Sets to be Used with Escape Sequences.
– ISO/IEC 10646:2003, Information technology – Universal Multiple-Octet Coded Character Set (UCS).
© ISO/IEC 2018 – All rights reserved
Rec. ITU-T X.697 (10/2017) 1
3 Definitions
For the purposes of this Recommendation | International Standard, the following definitions apply:
3.1 Specification of Basic Notation
For the purposes of this Recommendation | International Standard, all the definitions in Rec. ITU-T X.680 |
ISO/IEC 8824-1 apply.
3.2 Information Object Specification
For the purposes of this Recommendation | International Standard, all the definitions in Rec. ITU-T X.681 |
ISO/IEC 8824-2 apply.
3.3 Constraint Specification
This Recommendation | International Standard makes use of the following terms defined in Rec. ITU-T X.682 |
ISO/IEC 8824-3:
a) component relation constraint;
b) table constraint.
3.4 Parameterization of ASN.1 Specification
This Recommendation | International Standard makes use of the following term defined in Rec. ITU-T X.683 |
ISO/IEC8824-4:
– variable constraint.
3.5 Basic Encoding Rules (BER)
This Recommendation | International Standard makes use of the following terms defined in Rec. ITU-T X.690 |
ISO/IEC 8825-1:
a) data value;
b) dynamic conformance;
c) encoding (of a data value);
d) receiver;
e) sender;
f) static conformance.
3.6 Packed Encoding Rules (PER)
This Recommendation | International Standard makes use of the following terms defined in Rec. ITU-T X.691 |
ISO/IEC 8825-2:
a) composite type;
b) composite value;
c) outermost type;
d) relay-safe encoding;
e) simple type;
f) textually dependent.
3.7 Additional definitions
3.7.1 abstract syntax value: A value of an abstract syntax (defined as a set of values of a single ASN.1 type)
which is to be encoded by JER or which is generated by JER decoding.
3.7.2 associated encoding instruction (for a type): A set of JER encoding instructions associated with a type.
3.7.3 effective value constraint (of an integer type): The smallest integer range that includes all the values of the
integer type that are permitted by the JER-visible constraints (see clause 7.2.7).
3.7.4 effective size constraint (of a bitstring type): The smallest integer range that includes the lengths of all the
values of the string type that are permitted by the JER-visible constraints (see clause 7.2.8).
© ISO/IEC 2018 – All rights reserved
2 Rec. ITU-T X.697 (10/2017)
3.7.5 final encoding instructions (for a type): The set of JER encoding instructions associated with a type as a
result of the complete ASN.1 specification, and which are applied in producing encodings of that type.
3.7.6 inherited encoding instructions: A set of JER encoding instructions that are associated with the type
identified by a type reference.
3.7.7 JSON array: A series of JSON tokens that constitute an array structure as specified in ECMA 404, clause 7.
3.7.8 JSON member name string (of a component of a sequence, set, or choice type that is encoded as a JSON
object): The Unicode character string denoted by the name of the member of the JSON object identifying the
component in the JER encoding.
3.7.9 JSON number: A JSON token that is a number as specified in ECMA 404, clause 8.
3.7.10 JSON object: A series of JSON tokens that constitute an object structure as specified in ECMA 404, clause 6.
3.7.11 JSON string: A JSON token that is a string as specified in ECMA 404, clause 9.
NOTE – A JSON string is part of a JER encoding, it begins and ends with a quotation mark, may contain escapes, and is distinct
from the Unicode character string that it denotes.
3.7.12 JSON token: A Unicode character string that is one of the several kinds of tokens specified in ECMA 404,
clause 4.
3.7.13 JER encoding instruction: Notation used to change the JER encoding of a type.
3.7.14 JER-visible constraint: An instance of use of the ASN.1 constraint notation that affects the JER encoding of
a value.
3.7.15 octet: A group of eight consecutive bits, numbered from bit 8 (the most significant bit) to bit 1 (the least
significant bit).
3.7.16 prefixed encoding instruction: A JER encoding instruction that is assigned to a type using a type prefix.
NOTE – Prefixed encoding instructions can delete, replace, or add to the associated encoding instructions of a type.
3.7.17 targeted encoding instruction: A JER encoding instruction that is assigned to multiple types using a target
list in a JER encoding control section.
NOTE – Targeted encoding instructions can delete, replace, or add to the associated encoding instructions of multiple types.
4 Abbreviations
For the purposes of this Recommendation | International Standard, the following abbreviations apply:
ASN.1 Abstract Syntax Notation One
BER Basic Encoding Rules of ASN.1
JER JavaScript Object Notation Encoding Rules of ASN.1
PER Packed Encoding Rules of ASN.1
PDU Protocol Data Unit
5 Encodings specified by this Recommendation | International Standard
5.1 This Recommendation | International Standard specifies a set of encoding rules which can be used to encode
and decode the values of an abstract syntax defined as the values of a single (known) ASN.1 type. This clause describes
their applicability and properties.
5.2 JER encodings are always relay-safe provided the abstract values of the types EXTERNAL, EMBEDDED PDV,
and CHARACTER STRING are constrained to prevent the carriage of OSI presentation context identifiers.
5.3 If a type encoded with JER contains EXTERNAL, EMBEDDED PDV, or CHARACTER STRING types, then the outer
encoding ceases to be relay-safe unless the transfer syntax used for all the EXTERNAL, EMBEDDED PDV, or CHARACTER
STRING types is relay-safe.
NOTE – The character transfer syntaxes supporting all character abstract syntaxes of the form {iso standard 10646
level-1(1) …} are canonical. Those supporting {iso standard 10646 level-2(2) …} and {iso standard 10646
level-3(3) …} are not always canonical. All the above character transfer syntaxes are relay-safe.
5.4 JER encodings are self-delimiting. Encodings are always a whole multiple of eight bits. When carried in an
EXTERNAL type, they shall be carried in the OCTET STRING choice alternative, unless the EXTERNAL type itself is
encoded in JER, in which case the value may be encoded as a single ASN.1 type (i.e., an open type). When carried in an
© ISO/IEC 2018 – All rights reserved
Rec. ITU-T X.697 (10/2017) 3
OSI presentation protocol, the "full encoding" (as defined in Rec. ITU-T X.226 | ISO/IEC 8823-1) with the OCTET
STRING alternative shall be used.
5.5 This Recommendation | International Standard also specifies the syntax and semantics of JER encoding
instructions (see clauses 14 to 19).
5.6 ASN.1 forms a basic JSON schema notation. The ASN.1 schema is used to define the content and structure of
data using ASN.1 and the JavaScript Object Notation Encoding Rules. It can be used without JER encoding
instructions.
5.7 JER encoding instructions provide wider flexibility in the JSON texts that can be specified.
5.8 JER encoding instructions are assigned to ASN.1 type definitions or to type references using either or both of
JER type prefixes (see Rec. ITU-T X.680 | ISO/IEC 8824-1, clause 31.3) and a JER encoding control section (see
Rec. ITU-T X.680 | ISO/IEC 8824-1, clause 54). If encoding instructions are associated with a type definition, they are
carried with the ASN.1 type (through its type reference) into other type definitions and other ASN.1 modules. The final
encoding instructions of a type are applied when the type is encoded in JER and modify the JSON text produced.
6 Conformance
6.1 Dynamic conformance for the JavaScript Object Notation Encoding Rules is specified in clauses 7 to 41.
6.2 Static conformance is specified by those standards which specify the application of these encoding rules.
6.3 Alternative encodings are permitted by the JavaScript Object Notation Encoding Rules as encoder's options.
Decoders that claim conformance to JER shall support all JER encoding alternatives.
6.4 The rules in this Recommendation | International Standard are specified in terms of an encoding procedure.
Implementations are not required to mirror the procedure specified, provided the octet string produced as the complete
encoding of an abstract syntax value is identical to one of those specified in this Recommendation | International
Standard for the applicable transfer syntax.
6.5 Implementations performing decoding are required to produce the abstract syntax value corresponding to any
received octet string which could be produced by a sender conforming to the encoding rules identified in the transfer
syntax associated with the material being decoded.
6.6 If an ASN.1 specification assigns JER encoding instructions in accordance with clauses 8 to 13 such that an
ASN.1 type or component has final encoding instructions that violate the restrictions specified in clauses 14 to 19, then
that ASN.1 specification is not in conformity with this Recommendation | International Standard, even if (without the
encoding instructions) it would conform to all the requirements of Rec. ITU-T X.680 | ISO/IEC 8824-1.
NOTE – It is only occasionally invalid to assign an encoding instruction to a "Type", as it can be negated (removed from the set
of associated encoding instructions) by a further assignment. It is the final encoding instructions that determine conformity of the
specification.
7 General provisions
7.1 Use of the type notation
7.1.1 These encoding rules make specific use of the ASN.1 type notation as specified in 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, and can only be applied to encode the values of a single ASN.1 type specified using that notation.
7.1.2 In particular, but not exclusively, they are dependent on the following information being retained in the
ASN.1 type and value model underlying the use of the notation:
a) the identifiers of the components of a sequence or set type and of the alternatives of a choice type;
b) the identifiers of the enumeration items of an enumerated type;
c) whether a set or sequence type component has a default value or not;
d) the restricted range of values of a type which arise through the application of JER-visible constraints;
e) whether the type of a component is an open type.
7.2 Constraints
NOTE – The fact that some ASN.1 constraints may not be JER-visible for the purposes of encoding and decoding does not in any
way affect the use of such constraints in the handling of errors detected during decoding, nor does it imply that values violating
such constraints are allowed to be transmitted by a conforming sender. However, this Recommendation | International Standard
makes no use of such constraints in the specification of encodings.
© ISO/IEC 2018 – All rights reserved
4 Rec. ITU-T X.697 (10/2017)
7.2.1 In general the constraint on a type will consist of individual constraints combined using some or all of set
arithmetic, contained subtype constraints, and serial application of constraints.
The following constraints are JER-visible:
a) non-extensible size constraints on bitstring types;
b) non-extensible single value constraints and value range constraints on the base of a real type;
c) an inner type constraint that applies a non-extensible single value constraint or value range constraint to
the base of a real type;
d) a contained subtype constraint in which the constraining type carries a JER-visible constraint.
7.2.2 All other constraints are not JER-visible. In particular, the following constraints are not JER-visible:
a) constraints that are expressed in human-readable text or in ASN.1 comment;
b) variable constraints (see Rec. ITU-T X.683 | ISO/IEC 8824-4, clauses 10.3 and 10.4);
c) user-defined constraints (see Rec. ITU-T X.682 | ISO/IEC 8824-3, 9.1);
d) table constraints (see Rec. ITU-T X.682 | ISO/IEC 8824-3);
e) component relation constraints (see Rec. ITU-T X.682 | ISO/IEC 8824-3, 10.7);
f) constraints whose evaluation is textually dependent on a table constraint or a component relation
constraint (see Rec. ITU-T X.682 | ISO/IEC 8824-3);
g) extensible subtype constraints;
h) size constraints applied to a character string or octet string type;
i) single value subtype constraints applied to a character string type;
j) permitted alphabet constraints;
k) pattern constraints;
l) value and value range constraints on integer types;
m) constraints on real types except those specified in clause 7.2.1 (b);
n) constraints on the time type and on the useful and defined time types;
o) inner type constraints except those specified in clause 7.2.1 (c);
p) constraints on the useful types.
7.2.3 If a type is specified using a serial application of constraints, each of those constraints may or may not be
individually JER-visible. If the last subtype constraint of the series of constraints is JER-visible and contains an
extension marker, then that subtype constraint is extensible for the purposes of these encoding rules. Any other
constraint is not extensible for the purposes of these encoding rules, even if it contains an extension marker.
NOTE – In a serial application of constraints, each subtype constraint removes the extensibility specified in earlier constraints of
the series of constraints (see Rec. ITU-T X.680 | ISO/IEC 8824-1, 50.8).
7.2.4 If a constraint that is JER-visible is part of an INTERSECTION construction, then the resulting constraint is
JER-visible, and consists of the INTERSECTION of all the JER-visible parts (with the non-JER-visible parts ignored).
7.2.5 If a constraint that is not JER-visible is part of a UNION construction, then the resulting constraint is not JER-
visible.
7.2.6 If a constraint has an EXCEPT clause, the EXCEPT keyword and the following value set is completely ignored,
whether the value set following the EXCEPT keyword is JER-visible or not.
7.2.7 The effective value constraint of an integer type is an integer range determined as follows, taking into account
all the JER-visible constraints present in the type definition and ignoring any constraints that are not JER-visible:
a) the lower bound of the effective value constraint is the least permitted value of the integer type, if such a
value exists; otherwise, the effective value constraint has no finite lower bound;
b) the upper bound of the effective value constraint is the greatest permitted value of the integer type, if
such a value exists; otherwise, the effective value constraint has no finite upper bound.
NOTE – The only integer types that can have an effective value constraints with a finite lower or upper bound are the type of the
components of a real type, to which a value or value range constraint is applied by using an inner type constraint. Value
constraints on all other integer types are not JER-visible, and therefore the effective value constraint of those types has no finite
lower or upper bound.
© ISO/IEC 2018 – All rights reserved
Rec. ITU-T X.697 (10/2017) 5
7.2.8 The effective size constraint of a bitstring type is a single integer range determined as follows, taking into
account all the JER-visible constraints present in the type definition and ignoring any constraints that are not JER-
visible:
a) the lower bound of the effective size constraint is the length of the shortest permitted value of the string
type (possibly zero);
b) the upper bound of the effective size constraint is the length of the longest permitted value of the string
type, if such length is finite; otherwise, the effective size constraint has no finite upper bound.
7.3 Type and value model used for encoding
7.3.1 An ASN.1 type is either a simple type or a type built using other types. The notation permits the use of type
references and tagging of types. For the purpose of these encoding rules, the use of type references and tagging have no
effect on the encoding and are invisible in the model. The notation also permits the application of constraints and of
error specifications. JER-visible constraints are present in the model as a restriction of the values of a type. Other
constraints and error specifications do not affect encoding and are invisible in the JER type and value model.
7.3.2 A value to be encoded can be considered as either a simple value or as a composite value built using the
structuring mechanisms from components which are either simple or composite values, paralleling the structure of the
ASN.1 type definition.
7.4 Types to be encoded
7.4.1 Clauses 20 to 41 specify the encoding of the following types: boolean, integer, enumerated, real, bitstring,
octetstring, null, sequence, sequence-of, set, set-of, choice, object identifier, relative object identifier, internationalized
resource reference, relative internationalized resource reference, embedded-pdv, external, restricted character string,
unrestricted character string, time, and open types.
7.4.2 The selection type shall be encoded as an encoding of the selected type.
7.4.3 This Recommendation | International Standard does not contain specific provisions for the encoding of tagged
types as tagging is not visible in the type and value model used for these encoding rules. Tagged types are thus encoded
according to the type which has been tagged.
7.4.4 An encoding prefixed type is encoded according to the type which has been prefixed.
7.4.5 The useful types GeneralizedTime, UTCTime, and ObjectDescriptor shall be encoded as if they had
been replaced by their definitions given in Rec. ITU-T X.680 | ISO/IEC 8824-1, clause 45. Constraints on the useful
types are not JER-visible.
7.4.6 A type defined using a value set assignment shall be encoded as if the type had been defined using the
production specified in Rec. ITU-T X.680 | ISO/IEC 8824-1, 16.8.
7.5 Encoding instructions
7.5.1 JER encoding instructions modify the JSON text produced by the application of the JavaScript Object
Notation Encoding Rules to a type.
7.5.2 All occurrences of ASN.1 "Type" notation have an associated set (possibly empty) of JER encoding
instructions (the final encoding instructions). Encoding instructions are associated with a "Type" through:
a) (inherited encoding instructions) the presence of associated encoding instructions on the "Type" used in
the definition of a "typereference" used as a "Type";
b) (targeted encoding instructions) assignment of one or more JER encoding instructions to multiple types
using a JER encoding control section
...