RFC 1808 (rfc1808) - Page 2 of 16
Relative Uniform Resource Locators
Alternative Format: Original Text Document
RFC 1808 Relative Uniform Resource Locators June 1995 rather than re-specifying it within each instance. Relative URLs can also be used within data-entry dialogs to decrease the number of characters necessary to describe a location. In addition, it is often the case that a group or "tree" of documents has been constructed to serve a common purpose; the vast majority of URLs in these documents point to locations within the tree rather than outside of it. Similarly, documents located at a particular Internet site are much more likely to refer to other resources at that site than to resources at remote sites. Relative addressing of URLs allows document trees to be partially independent of their location and access scheme. For instance, it is possible for a single set of hypertext documents to be simultaneously accessible and traversable via each of the "file", "http", and "ftp" schemes if the documents refer to each other using relative URLs. Furthermore, document trees can be moved, as a whole, without changing any of the embedded URLs. Experience within the World-Wide Web has demonstrated that the ability to perform relative referencing is necessary for the long-term usability of embedded URLs. 2. Relative URL Syntax The syntax for relative URLs is a shortened form of that for absolute URLs [2], where some prefix of the URL is missing and certain path components ("." and "..") have a special meaning when interpreting a relative path. Because a relative URL may appear in any context that could hold an absolute URL, systems that support relative URLs must be able to recognize them as part of the URL parsing process. Although this document does not seek to define the overall URL syntax, some discussion of it is necessary in order to describe the parsing of relative URLs. In particular, base documents can only make use of relative URLs when their base URL fits within the generic-RL syntax described below. Although some URL schemes do not require this generic-RL syntax, it is assumed that any document which contains a relative reference does have a base URL that obeys the syntax. In other words, relative URLs cannot be used within documents that have unsuitable base URLs. 2.1. URL Syntactic Components The URL syntax is dependent upon the scheme. Some schemes use reserved characters like "?" and ";" to indicate special components, while others just consider them to be part of the path. However, there is enough uniformity in the use of URLs to allow a parser to resolve relative URLs based upon a single, generic-RL syntax. This generic-RL syntax consists of six components: Fielding Standards Track
