XML has emerged as the standard of meta language representing data format. It is rich, clear, extensible and self-description. All advantages make it the best candidate for representing data model.
The representative course of knowledge is a course in which the information state changes from self presence to self performance and an extensible thinking process of meta language.
知识表现的过程是信息由“自在”状态进入“自为”状态的过程,也是元语言的思维扩展过程。
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Moreover, components and composite components are self-described with extensible markup language (XML), and the latter are used as the containe.