As defined by RFC 3987 (http://www.ietf.org/rfc/rfc3987.txt). Internationalized Resource Identifiers (IRIs) are the internationalized version of URIs (which are also defined as a NamingSystem as https://terminology.hl7.org/4.0.0/NamingSystem-uri.html) that allow Unicode characters to be used in the identifier with some restrictions, which was defined by the Internet Engineering Task Force (IETF) in 2005. An IRI such as 'https://hi.wikipedia.org/wiki/हृदय' can be percent-encoded into the URI 'https://hi.wikipedia.org/wiki/%E0%A4%B9%E0%A5%83%E0%A4%A6%E0%A4%AF' to be used as a URL, but the IRI is easier to read, particularly for readers of non-Latin languages, and is natively supported by many tools, including many browsers, HTTP libraries, and in the Resource Description Framework (RDF).