In an open and self-description way, XML (extensible Markup Language) defines the data structure as well as the content and the structure, as it denotes the relationship between data.

• 可扩展标记语言(eXtensible Markup Language，XML)以一种开放的自我描述方式定义了数据结构，在描述数据内容的同时突出对结构的描述，从而体现出数据之间的关系。