So I’m here at the W3C Tech Plenary. I just finished a session on “URI-Based Extensibility: Benefits, Deviations, Lessons-Learned.” I’m curious how many people out there, which aren’t in a W3C working group, know the difference between URI and URL. How many of you had heard of the acronym URI? Post your answer in the comments.
I’d think that by throwing around terms like URI without least introducing it as a concept you’re creating another barrier to entry.
Oatmeal Stout - Justin Thorp's blog 
Of course there’s a difference, but it hasn’t been explained nearly enough. I’ll bet the only people who know tried to load a html dtd, only to find nothing there (before the w3c put something there, which in my opinion was a mistake).
Ah, Uniform Resource Identifier. I typically find that most people assume URI == URL. Several people I’ve worked with found it very confusing when they had to use URIs because they thought they had to use a URL to an existing resource.
What were the lessons-learned and conclusions of the session?
Yes, we could have done a better job introducing the terms. FYI, I wrote an article about it a couple years ago:
Untangle URIs, URLs, and URNs
Naming and the problem of persistence
Dan Connolly (connolly@w3.org), Technical Staff, W3C/MIT
21 Jun 2005
http://www-128.ibm.com/developerworks/xml/library/x-urlni.html
wats the diffrence b/w URL AND URI