Network Working Group                                           J. Kunze
Request for Comments: 1736                             IS&T, UC Berkeley
Category: Informational                                    February 1995


       Functional Recommendations for Internet Resource Locators

Status of this Memo

   This memo provides information for the Internet community.  This memo
   does not specify an Internet standard of any kind.  Distribution of
   this memo is unlimited.

1. Introduction

   This document specifies a minimum set of requirements for Internet
   resource locators, which convey location and access information for
   resources.  Typical examples of resources include network accessible
   documents, WAIS databases, FTP servers, and Telnet destinations.

   Locators may apply to resources that are not always or not ever
   network accessible.  Examples of the latter include human beings and
   physical objects that have no electronic instantiation (that is,
   objects without an existence completely defined by digital objects
   such as disk files).

   A resource locator is a kind of resource identifier.  Other kinds of
   resource identifiers allow names and descriptions to be associated
   with resources.  A resource name is intended to provide a stable
   handle to refer to a resource long after the resource itself has
   moved or perhaps gone out of existence.  A resource description
   comprises a body of meta-information to assist resource search and
   selection.

   In this document, an Internet resource locator is a locator defined
   by an Internet resource location standard.  A resource location
   standard in conjunction with resource description and resource naming
   standards specifies a comprehensive infrastructure for network based
   information dissemination.  Mechanisms for mapping between locators,
   names, and descriptive identifiers are beyond the scope of this
   document.

2. Overview of Problem

   Network-based information resource providers require a method of
   describing the location of and access to their resources.
   Information systems users require a method whereby client software
   can interpret resource access and location descriptions on their




 
RFC 1736                Recommendations for IRLs           February 1995


   behalf in a relatively transparent way.  Without such a method,
   transparent and widely distributed, open information access on the
   Internet would be difficult if not impossible.

2.1 Defining the General Resource Locator

   The requirements listed in this document impose restrictions on the
   general resource locator.  To better understand what the Internet
   resource locator is, the following general locator definition
   provides some contrast.

        Definition:  A general resource locator is an object
                     that describes the location of a resource.

   This definition deliberately allows many degrees of freedom in order
   to contain the furthest reaches of the wide-ranging debate on
   resource location standards.  Vast as it is, this problem space is a
   useful backdrop for discussion of the requirements (later) that
   generate a smaller, more manageable problem space.  A resource
   location standard shrinks the space again by applying additional
   requirements.

   Consider the definition in four parts: (1) A general resource locator
   is an object (2) that describes (3) the location of (4) a resource.

2.1.1.  A general resource locator is an object...

   The object could be a complex data structure.  It could be a
   contiguous sequence of bytes.  It could be a pair of latitude-
   longitude coordinates, or a three-color road map printed on paper.
   It could be a sequence of characters that are capable of being
   printed on paper.

2.1.2.  ...that describes

   In the fully general case, there are many ways that a resource
   locator could describe the location.  It could employ a graphical or
   natural language description.  It could be heavily encoded or