说明：  RSS是一种遵循w3c RDF规范的用于共享新闻标题和其他web内容的XML格式,本文阐述了RSS的定义,并尝试实现了一个RSS的解析器类.
(RSS is a kind of follow the w3c RDF specification for sharing news headlines and other web content in XML format, this paper expounds the definition of RSS, and try to implement a RSS parser class. )