统一架构 第6部分：映射

[中文适用范围]： IEC 62541-6:2025 规定了 IEC 62541-2 中描述的安全模型与 IEC 62541-4 中规定的抽象服务定义、IEC 62541-5 中定义的数据结构，以及可用于实现 OPC UA 规范的物理网络协议之间的映射关系。本第四版取消并替代了 2020 年发布的第三版。本版构成技术修订。与前一版相比，本版包含以下重大技术更改：a) 为 UA 安全对话增加对 ECC 的支持；b) 在证书撤销列表中使用 AuthorityKeyIdentifier 扩展；c) 对联合（Union）的 JSON 映射进行增强；d) 添加对十进制数据类型编码的支持；e) 描述 ECC 的 keyUsage 规则；f) 在 UANodeSet 定义中添加由 IANA 分配的媒体信息；g) 添加对用户和颁发者证书的要求；h) 添加当 DateTime 精度丢失时应遵循的规则；i) 添加允许截断包含嵌入式空字符的字符串的规则；j) 为 JSON 映射中 NodeId、ExpandedNodeId 和 QualifiedName 定义规范的字符串表示；k) 要求将 TAI 时间转换为 UTC；l) 在 JSON 编码中新增可在符号未知时省略符号的选项；m) 为 UANodeSet 添加支持 RolePermissions 所需的字段。 [外文原描述]： IEC 62541-6:2025 specifies the mapping between the security model described in IEC 62541‑2, the abstract service definitions specified in IEC 62541‑4, the data structures defined in IEC 62541‑5 and the physical network protocols that can be used to implement the OPC UA specification. This fourth edition cancels and replaces the third edition published in 2020. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: a) addition of support for ECC to UA Secure Conversation; b) use of the AuthorityKeyIdentifier extension in Certificate Revocation Lists; c) enhancement of JSON mapping of Unions; d) addition of Decimal data type encoding. e) description of ECC keyUsage rules; f) addition of Media assigned by IANA to UANodeSet definition; g) addition of requirements for user and issuer Certificates; h) addition of rules which specify what happens when DateTime precision is lost; i) addition of rules to allow for the truncation of strings containing embedded nulls. J) definition of a normative string representation for NodeId, ExpandedNodeId and QualifiedName for JSON mapping. k) requirement that TAI times be converted to UTC; l) new possibility to omit Symbol if unknown in JSON encoding; m) addition of fields needed to support RolePermissions to the UANodeSet