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

Bruce Whealton bruce at whealton.info
Wed Jun 29 18:10:26 CEST 2011

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
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:

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?

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 
           <rdfs:seeAlso rdf:resource=”http://url/pathto/foaf.rdf"/>

  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:

<owl:sameAs rdf:resource="http://pathToFileAboutPerson/hashURI"/>

  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).


  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
  Web Technology wiki: http://futurewavedesigns.com/w/

Dr Matthew Rowe
Research Associate
Knowledge Media Institute
The Open University, Walton Hall, Milton Keynes, MK7 6AA

The Open University is incorporated by Royal Charter (RC 000391), an exempt charity in England & Wales and a charity registered in Scotland (SC 038302).
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