[foaf-dev] beyond foaf:mbox_sha1sum

Steve Harris steve.harris at garlik.com
Tue Dec 22 14:26:13 CET 2009

On 22 Dec 2009, at 13:15, Story Henry wrote:

> On 22 Dec 2009, at 12:00, Mischa Tuffield wrote:
>> As for the blacklist of IFPs, we too have a blacklist of IFPs,  
>> which we flag up in the FOAF validator. We also found that many  
>> people use the foaf:homepage property to point to their browser's  
>> homepage. And as a result we had to blacklist, http:// 
>> www.google.com, yahoo.com, and bbc.co.uk to name a few.
> :-D That is funny. I had not thought of that way of reading the  
> foaf:homepage relation.
> The problem here as with mbox sha1 sum really is not the ontology,  
> it is wrong data on the web. (Though I think with sha1 sum there are  
> reasonable arguments that it is not an IFP).

I disagree about that one. There are cases with most (all?) of the  
other IFPs where a FOAF file may meet the spec, but they're not  
strictly inverse functional.

E.g. if I own http://foo.com/, and use that as my homepage, then the  
domain name lapses, someone else buys it and uses it as their homepage.

You have a FOAF document, last updated 2009 saying:

#steve foaf:homepage <http:/foo.com/> .

and one from 2010 saying

#alice foaf:homepage <http://foo.com/> .

Neither of them is/was incorrect, but foaf:homepage is not really an  
IFP in this case. However these cases are sufficiently rare that you  
can get away with it, and any sufficiently comprehensive FOAF  
processor has to deal with loads of issues like this anyway (caused by  
typos, mistakes and so on).

> To stop this one has to find friendly ways to make people think  
> correctly about what they are doing. This is a subtle user interface  
> job. It has to be somewhat similar to what we do when someone makes  
> a mistake in speaking. So if someone says they are the last  
> remaining ancestor of the King of Scotland [1] we could laugh out  
> loud, or suggest that they look very good for their age.

Sure, but the problem is that a lot of FOAF is exported from other  
systems, and the other systems usually just wanted something to link  
from the users "homepage" profile text, a link to the BBC is pretty  
harmless there.

Sites exporting FOAF could go back and make their users all verify  
that the think they've said is a "homepage" is what we think of as a  
homepage, but that seems a little unlikely.

- Steve

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