[uf-discuss] hatom tumblr theme

Martin McEvoy martin at weborganics.co.uk
Mon Dec 15 11:54:28 PST 2008

Hello Toby, James

Toby A Inkster wrote:
> James Tindall:
>> Incidentally however, this vcard validator now complains that uid should
>> not appear twice on a page with the same value?
>> http://hcard.geekhood.net/?url=microformats.tumblr.com
> There is no prohibition on reusing UIDs in the hCard spec, but 
> hcard.geekhood.net goes far beyond the spec with regards to suggesting 
> best practices and things you might have missed. In general, I think 
> it's a good tool, but in this case I (personally) disagree with it.
> If Joe has an hCard for himself on his index.html and another hCard 
> for himself on his contact-me.html, then nobody would think twice 
> about giving them both the same UID. So if two hCards on different 
> pages can have the same UID, then why not two hCards on the same page? 
> What is important (and again this is just my opinion) is that if two 
> hCards do have the same UID (whether they're on different pages or the 
> same page), then they should be referring to the same contact (person, 
> organisation, place, whatever).
> To back up my argument, I'll cite the vCard spec (RFC 2426) which 
> defines the purpose of "UID" as:
>> To specify a value that represents a globally unique
>> identifier corresponding to the individual or resource
>> associated with the vCard.
> That is, the UID is a unique identifier for the contact, not a unique 
> identifier for the card.
Nope you will find that the UID is for the entire vcard....
> I've contacted Kornel about this warning message and suggested that he 
> change it so that the warning is only issued if two hCards have the 
> same UID but different FNs.

I would say that is wrong too, what is wrong with that is how authors 
commonly mark up the UID of a hCard in microformats eg:

<a class="url uid" href="http://myfoosite.com/">myfoosite</a>

where this all falls apart is that if there is more than one regular 
author of a site they might all want to use the same url, Its easily 
solvable by adding @id to a hCard and using a relative url

<a class="url uid" href="http://myfoosite.com/#person1">myfoosite</a>

<a class="url uid" href="http://myfoosite.com/#person2">myfoosite</a>

All that aside UID should *only* really be used once on a page to define 
a single authoritative point of contact, using more than one UID really 
seems to defeat the object when you think about it..
> As an aside, I'll point out that I do *not* recommend using the same 
> UID for the historic hCards in a resume, because in that situation, 
> merging details is not the desired behaviour - you want them to be 
> kept separate.

Best Wishes.

Martin McEvoy


"You may find it hard to swallow the notion that anything as large and apparently inanimate as the Earth is alive."
Dr. James Lovelock, The Ages of Gaia

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