Network Working Group                                     T. Berners-Lee
Request for Comments: 1738                                          CERN
Category: Standards Track                                    L. Masinter
                                                       Xerox Corporation
                                                             M. McCahill
                                                 University of Minnesota
                                                                 Editors
                                                           December 1994


                    Uniform Resource Locators (URL)(‘±‚«)


2. General URL Syntax

   Just as there are many different methods of access to resources,
   there are several schemes for describing the location of such
   resources.

   The generic syntax for URLs provides a framework for new schemes to
   be established using protocols other than those defined in this
   document.

   URLs are used to `locate' resources, by providing an abstract
   identification of the resource location.  Having located a resource,
   a system may perform a variety of operations on the resource, as
   might be characterized by such words as `access', `update',
   `replace', `find attributes'. In general, only the `access' method
   needs to be specified for any URL scheme.

2.1. The main parts of URLs

   A full BNF description of the URL syntax is given in Section 5.

   In general, URLs are written as follows:

       :

   A URL contains the name of the scheme being used () followed
   by a colon and then a string (the ) whose
   interpretation depends on the scheme.

   Scheme names consist of a sequence of characters. The lower case
   letters "a"--"z", digits, and the characters plus ("+"), period
   ("."), and hyphen ("-") are allowed. For resiliency, programs
   interpreting URLs should treat upper case letters as equivalent to
   lower case in scheme names (e.g., allow "HTTP" as well as "http").