!!! Overview[1]
[{$pagename}] is the top level of the [Uniform Resource Identifier] ([URI]) naming structure in computer networking.

[{$pagename}] are in an [IANA Registry] at [Uniform Resource Identifier (URI) Schemes|https://www.iana.org/assignments/uri-schemes/uri-schemes.xhtml|target='_blank']

All [URIs] and [Absolute URI] references are formed with a scheme name, followed by a colon character (":"), and the remainder of the [URI] often called 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.

The scheme name consists of a sequence of characters beginning with a letter and followed by any combination of:
* letters
* digits
* plus ("+")
* period (".")
* hyphen ("-").
Although [{$pagename}] are [case-insensitive], the canonical form is lowercase and documents that specify [{$pagename}] must do so with lowercase letters. The scheme name is followed by a colon (":").
!! More Information
There might be more information for this subject on one of the following:
[{ReferringPagesPlugin before='*' after='\n' }]
----
* [#1] - [URI Scheme|Wikipedia:URI_scheme|target='_blank'] - based on 2015-02-17