Things” in the semantic web, even very abstract ones, are uniquely named by URIs. 在语义网络中的万物，每一个抽象目标，都可以唯一的被URI命名。
    A URI is an identifier, not necessarily a locator as is a URL. URI是一个标识符，不一定像网址一样是一个定位器。
    IRIs (International Resource Identifiers) allow extended characters and can be used in place of URIs. IRI允许扩展字符，可以用来代替URI
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    URI Syntax:
    : [? ] [# ]
    Examples:

    • ANU website: http://www.anu.edu.au/. This is a URL but is reused as a URI referring to the thing that is the ANU website.
    • The actual ANU itself: http://anu.edu.au/resource#id. This is a URI that refers to the thing that is the Australian National University. It also happens to be a URL.
    • URIs include URNs (e.g., urn:oid:2.16.840 e.g. urn:doi:10.1109/MIS.2013.102)