XML是W3C（万维网联盟）定义的技术标准 可用于标准化ISO 20022的物理表示（即语法） 信息。XML在特定领域的具体使用方式上有很大的自由 应用因此，仅仅声明使用了XML并不足以保证 可预测性；还必须解释如何使用它。本技术规范包含一组XML设计规则，称为ISO 20022 XML。这些设计规则定义了如何通过消息来描述标准化消息 根据ISO/TS 20022-3的建模指南，UML1中的定义必须 表示为符合ISO 20022的有效XML文档。有效的XML文档（以下称为“XML实例”或“实例”）如下所示: W3C定义的任何XML文档都有相关的描述 符合该说明中表示的约束条件。相关描述 在本例中，源于消息定义，该定义最初在中描述 UML。本技术规范还描述了UML消息的（一部分）方式 定义可以转换为W3C XML模式。然后，将使用这个XML模式 可以使用验证XML模式解析器自动验证 给定的XML实例符合 消息定义。DTD（文档类型定义）也可用于验证文档的部分符合性 将XML实例添加到其相应的消息定义中。然而，由于 DTD提供的验证功能有限，本文档不包括XML DTD。请注意，本文档仅解释了给定的消息定义图将如何 可以映射为XML。它没有解释如何创建消息定义图。 该信息可在ISO/TS 20022-3建模指南中找到。

XML is a technical standard defined by W3C (the World Wide Web Consortium) that can be used for the physical representation (i.e. the syntax) of standardized ISO 20022 Messages. XML leaves a lot of freedom for the exact way it is used in a particular application. Therefore, merely stating that XML is used is not sufficient to guarantee predictability; one must also explain HOW it will be used.This Technical Specification contains a set of XML design rules, called ISO 20022 XML. These design rules define how a standardized Message - described by a Message Definition in UML1 according to the Modelling Guidelines of ISO/TS 20022-3 must be represented as a valid ISO 20022 compliant XML document.A valid XML document (referred to hereafter as 'XML instance' or 'instance') as defined by W3C is any XML document that has an associated description and that complies with the constraints expressed in that description. The associated description in this case is derived from the Message Definition, which is originally described in UML.This Technical Specification also describes how (a part of) the UML Message Definition can be converted into a W3C XML Schema. This XML schema will then make it possible to use a validating XML schema parser to automatically verify that a given XML instance complies with (a subset of) the constraints described in the Message Definition.DTDs (Document Type Definitions) could also be used to validate partial compliance of an XML instance to its corresponding Message Definition. However, because of the limited validation functionality DTDs offer, this document does NOT cover XML DTDs.Note that this document merely explains how a given Message Definition Diagram will be mapped into XML. It doesn't explain how to create a Message Definition Diagram. This information can be found in ISO/TS 20022-3 Modelling guidelines.