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Andy Wardley abw at
Thu Feb 9 12:04:02 GMT 2006

Dominic Mitchell wrote:
> Then you've got a broken web site -- period.  Content should have only
> one, canonical URL.

Not so.  Remember that a URL is a Universal Resource Locator.  It simply 
says that there is a resource that can be fetched from this location.  It
doesn't say that this is the only location for the resource, or that the
resource will be there tomorrow or the day after.

For example, both these URLs point to the same resource:

Both are correct, both are equally valid.

Homotopic paths (different paths that get you to the same place) are 
a fundamental part of any hyperspace such as the web, and a good thing too.  
There is no strict hierarchy, there is no "One True Location".  That's 
why it's a web and not an index.

On the other hand, every resource should ideally have one, canonical URI.
A Universal Resource Identifier does not say anything about the location
of the resource, but simply gives it an identifier so that it can be 
uniquely referenced now and for the rest of time.  You may not be able
to fetch the resource, now or ever, but at least you'll be able to talk 
about it.

I suspect this is what you're really getting at.  The URL/URI confusion
is a common one, made all the more perplexing by the fact that URLs are
written using the URI "syntax".  Thus in common parlance, URL and URI are
interchangeable but actually relate to slightly different concepts.


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