URIs are the identifiers of the Semantic Web. They leverage the well-developed URLs of the Web, but also permit URNs that are not URLs.

    Technically, we should be speaking or “IRIs” that use an internationalised chacter set, but the term “URI” is popularly used.

    Tim Berners-Lee’s “four rules” (2006)
    http://www.w3.org/DesignIssues/LinkedData.html
    1. Use URIs as names for things 用URIs作为事物的名称
    2. Use HTTP URIs so that people can look up those names 使用超文本传输协议URIs,这样人们就可以查找这些名字
    3. When someone looks up a URI, provide useful information, using the standards (RDF*, SPARQL) 当有人查找URI时,使用标准提供有用的信息
    4. Include links to other URIs so that they can discover more things. 包括到其他URIs的链接,这样他们可以发现更多的东西。

    •See also “Cool URIs for the Semantic Web”, (2008) http://www.w3.org/TR/cooluris/