[uf-discuss] Coding mbox_sha1sum in XFN

Toby A Inkster mail at tobyinkster.co.uk
Sat Apr 26 03:48:08 PDT 2008

Julian Bond wrote:

> I want to be able to say something like:-
> This person with this profile page URL and this mbox_sha1sum is one of
> my contacts.
> But I'm not sure how to do it in XFN. Where can I put mbox_sha1sum  
> into
> <a href="url" rel="contact>their name</a>

For the href attribute, you could use a (non-standard, but frequently  
used[1]) SHA1 URN:

	<a href="urn:sha1:052f384479559f1b4854756bdce69d1c658de3b3"
	rel="contact">Their Name</a>

It should be supported by most XFN parsers that treat the URL as  
basically an opaque identifying string. Any XFN parsers that assume  
that the href attribute will be an HTTP URI may have problems, but  
that would be their own fault for making such an assumption.

Of course, if you're using it on a web page designed for humans, you  
should bear in mind that people clicking on the links might get  
confusing error messages if they don't have any program configured to  
handle such URIs (and I can't imagine that any such programs exist!),  
so it might be inadvisable to use such links on such a web page. One  
way of mitigating this problem might be to style these "urn:" links  
(using CSS) as if they were plain, non-link text. (Don't forget to  
use the CSS "cursor" property to disable the pointing hand cursor.)

1. Google for "urn:sha1" (in quotes) returns almost a quarter of a  
million results. It's mostly used for P2P, but that shouldn't stop us  
re-employing it here.

Toby A Inkster
<mailto:mail at tobyinkster.co.uk>

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