DTD简介 n有效的文档( use greeting. dtd) <GREETING>various random text but no markup</GREETING> 无效的文档 <GREETING><sometag>random text</sometag> <someEmpty Tag/></GrEETING>DTD简介 „ 有效的文档 (use greeting.dtd) use greeting.dtd) <GREETING>various random text but no markup</GREETING> „ 无效的文档 <GREETING><sometag>random te t</sometag> <GREETING><sometag>random text</sometag> <someEmptyTag/></GREETING>