ISO/IEC 13250-4:2009定义了一种称为Canonical XTM（简称CXTM）的格式。该格式是一种XML格式，其特性是，它保证两个等效的主题映射数据模型实例（ISO/IEC 13250-2）将始终生成逐字节相同的序列化，而非等效实例将始终生成不同的序列化。因此，CXTM可以直接比较两个主题映射，通过比较它们的规范序列化来确定相等性。CXTM的目的是允许为各种主题图创建测试套件- 只要支持CXTM，即可在不同的主题地图实现之间轻松移植的相关技术。CXTM不打算用于主题地图的交换，尽管这是可能的。主题地图交换的标准格式是XTM（ISO/IEC 13250-3）。 ISO/IEC 13250-4:2009规定了如何通过从主题地图数据模型（ISO/IEC 13250-2）到XML信息集的转换，从主题地图生成CXTM文件。

ISO/IEC 13250-4:2009 defines a format known as Canonical XTM, or CXTM for short. The format is an XML format, and has the property that it guarantees that two equivalent Topic Maps Data Model instances (ISO/IEC 13250-2) will always produce byte-by-byte identical serializations, and that non-equivalent instances will always produce different serializations. CXTM thus enables direct comparison of two topic maps to determine equality by comparison of their canonical serializations. The purpose of CXTM is to allow the creation of test suites for various Topic Maps-related technologies that are easily portable between different Topic Maps implementations, so long as these support CXTM. CXTM is not intended to be used for the interchange of topic maps, although this is possible. The standard format for interchange of topic maps is XTM (ISO/IEC 13250-3). ISO/IEC 13250-4:2009 specifies how CXTM files are produced from topic maps by means of a transformation from the Topic Maps Data Model (ISO/IEC 13250-2) to the XML Infoset.