Uniform Resource Locators
By Randy D. Ralph, MLIS, Ph.D.
In place 1996. Last update December 29, 2000. Copyright © 1996 - 2002 Randy D. Ralph
The Structure of URLs
A Uniform Resource Locator (URL - pronounced Earl, as in "Duke of...") is nothing more than an Internet address. Don't let the format throw you. Basically, it's set up like this:
The PROTOCOL (http://) is the HOW
The HOST DOMAIN NAME (www.mydomain.net) is the WHERE
The DIRECTORY PATH (~rdralph/rdralph/) is the WHO/WHAT
So the whole URL is:
Meaning: take me to rdralph's randy directory at www.netunlimited.net using the http (hypertext transfer) protocol and load the default page.
Common Internet Protocols
There are several protocols used commonly on the Internet to get to a variety of sites which support them. They are listed in the table below. The protocol which supports the World Wide Web - just one component of the Internet - is http - hypertext transfer protocol.
NOTE: Most computer systems reachable via the Internet will be running some flavor of Unix. Unix systems are generally case-sensitive; that is, upper and lower case makes a difference to them, so observe and copy URLs carefully, noting upper and lower case letters. Also remember that all computers are literal unto the death, so you'll have to get the URL exactly right or it's no go. If you get an error message from your browser when you enter an URL yourself, check it carefully for upper and lower case letters and remember to include the all the colons (:), slashes (//) and tildes (~) in the right places.
Host Domain Names
Host Domain Names can look daunting but if you understand the structure and naming conventions they start to make a lot of sense. Generally, they have the form:
The only really tricky part is the Service or Machine name. Most WWW hosts use the service name WWW - it makes sense. The Location name is almost always mnemonic - an abbreviation of the location name or an acronym for it. A lot of the time the location name is not abbreviated at all. The Domain gives you some interesting information about the WWW site, especially if it's located within the United States. Below is a table of common domain acronyms used for WWW sites in the United States:
So, it's clear that the domain can tell you what type of site you can expect to be visiting.
Some sites in the United States and most sites in Europe and elsewhere use a geographical approach in their domains. The last two positions in the domain of a WWW site outside the United States will often tell you the country. Universal two-letter country codes are used. For example: fi = Finland, za = South Africa, uk = The United Kingdom, etc.
Sites in the United States that use the geographical approach can look pretty complex. For example, the domain for Guilford Technical Community College is: technet.gtcc.cc.nc.us - meaning, technet at Guilford Technical Community College, community colleges, North Carolina, United States. So, even the most complicated-looking ones do make sense.
Paths in URLs
There's not much to say about this. You've just got to know the correct path to the information you want at the site. This information is almost always provided to you correctly as part of the link you followed to get to a site, but remember that HTML developers are human and make errors, too. The paths to informatin at Internet sites really can't be divined, even with a crystal ball, except, possibly, when it comes to the names of people, and even that's problematic.
By now you've probably seen the tilde - ~. The tilde - pronounced like the name "Tilda" - generally precedes the name of a directory assigned to a person (although it's not uncommon for people to use "cute" aliases on the Internet instead of their real names). In the URL http://www.netunlimited.net/~rdralph/, for example, the rdralph part indicates an account name associated with the author - Randy D. Ralph. As you become more familiar with the WWW you'll begin to recognize and understand how to navigate using partial paths. Do watch out for the tilde - leaving it out is one of the most common errors in keying URLs.
If you have any questions, suggestions or comments please contact:
Randy D. Ralph