On Jan 4, 2007, at 2:16 PM, Roy T. Fielding wrote:

> The ultimate goal is to choose the one true identifier that will
> always map to the intended resource, such that the link author (and
> the millions of people who subsequently copy or bookmark that link)
> never have to change the link. Of course, we rarely achieve the
> ultimate goal the first time, and sometimes there are many paths to
> the ultimate goal that get explored along the way, and sometimes
> people move the goal posts.
>
> If there are many URIs for a given resource, the best implementation
> is for all of the other URIs to redirect to the one URI that is
> deemed to be "best" for the resource's unique semantics. The reason
> for that is not REST or Web Architecture (though both are specifically
> designed to enable it): the reason is network economics as expressed
> by power laws, Metcalfe's law, PageRank, and a hundred other
> restatements of the factors that place value on social networks.

I understand how that should help search engines count how many
references there are for calculating page rank, but could you
elaborate how canonical URLs affect "Metcalf's law, power laws, and a
hunder other restatements..."

I did take the canonical URL thing to heart in our new architecture.
It may be a bit over-designed but we generate controllers that
canonicalize by dropping trailing slashes and even reordering the
query parameters. For example:

http://www.artima.com/articles?t=java&p=4&o=a
http://www.artima.com/articles?p=4&o=a&t=java
http://www.artima.com/articles?t=java&o=a&p=4
http://www.artima.com/articles?p=4&t=java&o=a
http://www.artima.com/articles?o=a&p=4&t=java
http://www.artima.com/articles/?t=java&p=4&o=a
http://www.artima.com/articles/?p=4&o=a&t=java
http://www.artima.com/articles/?t=java&o=a&p=4
http://www.artima.com/articles/?p=4&t=java&o=a
http://www.artima.com/articles/?o=a&p=4&t=java
http://www.artima.com/articles/?o=a&t=java&p=4

All get redirected to:

http://www.artima.com/articles?o=a&t=java&p=4

Currently there is one URI that doesn't get redirected to the
canonical form. It's on my list to fix that:

http://artima.com/articles?o=a&t=java&p=4

Bill
----
Bill Venners
President
Artima, Inc.
http://www.artima.com

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