RFC 1738 (rfc1738) - Page 2 of 25
Uniform Resource Locators (URL)
Alternative Format: Original Text Document
RFC 1738 Uniform Resource Locators (URL) December 1994
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").
2.2. URL Character Encoding Issues
URLs are sequences of characters, i.e., letters, digits, and special
characters. A URLs may be represented in a variety of ways: e.g., ink
on paper, or a sequence of octets in a coded character set. The
interpretation of a URL depends only on the identity of the
characters used.
In most URL schemes, the sequences of characters in different parts
of a URL are used to represent sequences of octets used in Internet
protocols. For example, in the ftp scheme, the host name, directory
name and file names are such sequences of octets, represented by
parts of the URL. Within those parts, an octet may be represented by
Berners-Lee, Masinter & McCahill