[foaf-dev] Linking foaf and other rdf documents/resources

Mischa Tuffield mischa.tuffield at garlik.com
Wed Jun 29 18:22:53 CEST 2011

Hi Bruce, 


On 29 Jun 2011, at 17:10, Bruce Whealton wrote:

> Thanks Matthew.  This relates to my question regarding Mischa’s response where I asked what exactly is the meaning of the use of the hash symbol in references, for example:
> #me or #BruceWhealton like this:
> http://brucewhealton.us/BruceWhealton/foaf.rdf#me or
> http://brucewhealton.us/BruceWhealton/foaf.rdf#BruceWhealton

<http://example.com/foaf> a foaf:Document . 
<http://example.com/foaf> foaf:primaryTopic <http://example.com/foaf#bruce> . 
<http://example.com/foaf#bruce> a foaf:Person . 

By using a hash fragment above one is creating a new URI for the foaf:Person, so that when some grabs the document on the web describing you, e.g. http://example.com/foaf, they know that http://example.com/foaf is the URI for the document which describes you, and http://example.com/foaf#bruce is the URI which represents you. 

This allows one to make statements about you the foaf:Person and about the document which has facts about you the foaf:PersonalProfileDocument. 

Basically you are making two URIs one for YOU and one for the DOCUMENT which describes you. <http://example.com/foaf> != <http://example.com/foaf#bruce> . 

> yes the latter is getting redundant in the use of my name.  I had put different FOAF files in folders that match their name.  That way I can name all the FOAF files as foaf.rdf
> So, the file about my wife is here:
> http://brucewhealton.us/ElnazWhealton/foaf.rdf

There is nothing stopping you from creating URI for lots of people in one file : 



> It also occurred to me, regarding what Mischa was saying about unambiguously referring to a person by adding an email address that if one were referring to historical persons, or one’s ancestors using
> FOAF and other vocabularies, they don’t have email addresses.  So, I cannot distinguish between my grandfather and my great-great grandfather, who both had the same name, using an email address.  If they are both in the same RDF file, I believe I would need to use a nodeID on a foaf:Person container to uniquely refer to each of them.  Does that make sense?

Sure, if you don't have any unique identifiers for the people, you can mint them their own URIs so that you can identify them unambiguously, see above ^^


> Thanks,
> Bruce
> From: Matthew Rowe
> Sent: Wednesday, June 29, 2011 4:39 AM
> To: Bruce Whealton
> Cc: foaf-dev at lists.foaf-project.org
> Subject: Re: [foaf-dev] Linking foaf and other rdf documents/resources
> Hi Bruce
> On 29 Jun 2011, at 01:11, Bruce Whealton wrote:
>> Hello all,
>>                 So, there are a few ways that one can link various profiles, or RDF FOAF files/resources.  I’m wondering if there is a best practice.
>> I had been using
>> <foaf:knows>
>>         <foaf:Person>
>> ...
>>          <rdfs:seeAlso rdf:resource=”http://url/pathto/foaf.rdf"/>
>>         </foaf:Person>
>> </foaf:knows>
>> But some FOAF profiles I’ve seen setup with method #2.
>> <rdf: Description rdf: about=”http://pathToFileAboutPerson/longstringofcharacters” >
>>       ... information about the person
>> </rdf: Description>
>> then further down there would be a
>> <foaf: knows resource=”http://pathToFileAboutPerson/longstringofcharacters”/>
>> I assume that the about="http://pathToFileAboutPerson/longstringofcharacters” refers to a FOAF file but I guess it doesn’t have to link to a foaf file.
>> I wonder if there is a benefit to using method #2 or a best practice that favors this? 
> I don't think that there is a best practice per se, as both are, as you have found, commonly used conventions. Another is to place a link to an equivalent foaf:Person instance using owl:sameAs within the foaf:Person instance in a foaf profile:
> <foaf:knows>
> <foaf:Person>
> .....
> <owl:sameAs rdf:resource="http://pathToFileAboutPerson/hashURI"/>
> </foaf:Person>
> </foaf:knows>
>> I can see that it might make it easier if one had to refer, more than once, to the resource that represents a person (through their FOAF profile) in a document.
>> As one uses more vocabularies and has more extensive rdf files, it becomes more likely that one is going to make numerous assertions about that person (resource). 
> My preference is for your latter example over the former as data is not duplicated in this instance. However, if I was to create new information about a person (for example by exporting it from a Social Web platform) then I would go for the former option of creating a new instance of foaf:Person and then associating additional, existing information about the person to this instance using either rdfs:seeAlso or owl:sameAs.
>> Most importantly though, will there be any difference in the ability of crawlers or other apps to follow the links between various FOAF profile files?
> In theory, no. Any crawler should have built in 'lookups' that traverse the links and dereference any URIs that are described as being equivalent or providing additional information about the instance (i.e. rdfs:seeAlso and owl:sameAs).
>> Thanks,
>> Bruce
>> ++++++++++++++++++++++++++++++++++++++++++++++++++
>> Bruce Whealton, Owner Future Wave Designs
>> FOAF: http://whealton.info/BruceWhealton1/foaf.rdf
>> Vcard: http://whealton.info/BruceWhealton1/brucewhealtonvcard.html
>> Web Design and Development http://FutureWaveDesigns.com
>> http://futurewavedesigns.com/wordpress/
>> Web Technology wiki: http://futurewavedesigns.com/w/
>> ++++++++++++++++++++++++++++++++++++++++++++++++++
>> <ATT00001..txt>
> --
> Dr Matthew Rowe
> Research Associate
> Knowledge Media Institute
> The Open University, Walton Hall, Milton Keynes, MK7 6AA
> http://people.kmi.open.ac.uk/rowe/ 
> -- 
> The Open University is incorporated by Royal Charter (RC 000391), an exempt charity in England & Wales and a charity registered in Scotland (SC 038302).
> _______________________________________________
> foaf-dev mailing list
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Mischa Tuffield PhD
Email: mischa.tuffield at garlik.com
Homepage - http://mmt.me.uk/
+44(0)208 439 8200  http://www.garlik.com/
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Registered office: Thames House, Portsmouth Road, Esher, Surrey, KT10 9AD

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