[wp-hackers] Why URL in GUID?

Sam Angove sam at rephrase.net
Tue Oct 3 01:27:25 GMT 2006

On 10/3/06, Paul Menard <codehooligans at codehooligans.com> wrote:
> The only I have is if this value must be unique, why is it not a
> unique key in the database. More specific, why is it not 'the' unique
> key?

It's not *just* a unique key. It's used in Atom feeds for the `id`
element, for example, which is required by the spec to be a valid IRI.
In Atom 0.3 it was required to be a URI. That limits the format fairly

Anyone looking into it should read this article by Mark Pilgrim: [1]

[1]: http://diveintomark.org/archives/2004/05/28/howto-atom-id

He recommends using tag URIs [2]. Some examples:

    tag:timothy at hpl.hp.com,2001:web/externalHome

They're still readable and informative, but aren't going to be
mistaken for HTTP URLs. I don't think any of the other options are as

[2]: http://www.ietf.org/rfc/rfc4151.txt

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