ISO/IEC 8825-4:2021 信息技术 ASN.1编码规则 第4部分：XML编码规则（XER）

标准编号：ISO/IEC 8825-4:2021

中文名称：信息技术 ASN.1编码规则 第4部分：XML编码规则（XER）

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

发布日期：2021-06

标准范围

本文档指定了一组基本XML编码规则（BASIC-XER），可用于导出Rec中定义的类型的值的传输语法。ITU-T X.680 ISO/IEC 8824-1和建议。ITU-T X.681 ISO/IEC 8824-2。本文档还指定了一组规范XML编码规则（CXER），这些规则提供了对基本XML编码规则的约束，并为任何给定的ASN.1值生成唯一的编码。本文档进一步指定了一组扩展XML编码规则（EXTENDED-XER），它增加了更多的编码器选项，还允许ASN.1说明符改变由BASIC-XER产生的编码。这些编码规则的规范中隐含着它们也用于解码。本文档中指定的编码规则:-在通信时使用；-旨在用于显示值和/或使用通常可用的XML工具(例如浏览器)处理它们是选择编码规则的主要关注点的情况下；-允许通过为Rec中描述的所有形式的可扩展性添加额外值来扩展抽象语法。ITU-T X.680 ISO/IEC 8824？1.该文档还指定了XER编码指令的语法和语义，以及它们的赋值和组合规则。XER编码指令可用于控制特定ASN.1类型的扩展XER编码。

This document 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 document 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 document 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 document :
– 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.
This document 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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