URI scheme

A URI scheme is the top level of the URI (Uniform Resource Identifier) naming structure. All URIs and absolute URI references are formed with a scheme name, followed by a colon character, and the remainder of the URI called (in the outdated RFCs 1738 and 2396, but not the current STD 66/RFC 3986) the scheme-specific part. The syntax and semantics of the scheme-specific part are left largely to the specifications governing individual schemes, subject to certain constraints such as reserved characters and how to "escape" them.
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