A valid absolute URI must have three parts:
A scheme name that defines
what kind of URI it is. The most common example is
http, which specifies the Hypertext
Transfer Protocol used by the World Wide Web.
A colon character, “:”
A scheme-specific part follows the colon. The syntax of this part depends on the scheme name.
For example, in the URI
“http://www.nmt.edu/tcc/”, the
scheme name is “http” and
the scheme-specific part is “//www.nmt.edu/tcc/”.