Uniform Resource Locators

A Uniform Resource Locator, or URL, is a unique name that identifies a part of a node somewhere in the world. A URL consists of five parts: In Xanadu (a fully distributed hypertext system, developed by Ted Nelson at Brown University, from 1965 on) there was only one protocol, so that part could be missing. Within a node every possible (contiguous) subpart could be the destination of a link.

In the World Wide Web the standard protocol is http, the HyperText Transfer Protocol. However, other protocols such as gopher, ftp and telnet can be used with most browsers as well. The destination anchor must be defined in the node. So only parts of a node that are indicated by the author can be selected.

The syntax of a URL for the World Wide Web is:

   protocol://host:port/nodename#anchorname
The complete syntax description for URLs can be found in two standard documents: rfc1738 for absolute addresses and rfc1808 for relative addresses. Common errors when first creating HTML documents are: These errors may not be apparent when using "file:" urls on a Windows'95 system for instance, but they appear when using an http (Web) server on a Unix system. When you make these errors in the final assignment of this course you will not get a grade until you correct them.

If you are reading this document using any one of the popular browsers the URL and title of the current document are always displayed.