[uf-discuss] A (big) problem with XFN: identity of source and target not findable

[David Janes]

Wow. A spec just like Aphrodite, born fully an adult.

On Wed, Mar 19, 2008 at 8:11 PM, Ryan King <ryan at theryanking.com> wrote:
> This is not a big problem, its mostly solved with [1]
>
>  -ryan
>
>  1. http://microformats.org/wiki/representative-hcard
>
>
>
>  On Mar 18, 2008, at 5:31 AM, Costello, Roger L. wrote:
>
>  > Hi Folks,
>  >
>  > Flickr uses XFN.  Here is a sample Flickr page that uses XFN:
>  > http://www.flickr.com/people/tantek/
>  >
>  > At the browser menu select View >> Page Source.  Then search for rel=
>  >
>  > Here's an example usage of XFN within that Flickr page:
>  >
>  > <a href="/photos/24172116 at N08/" rel="contact">
>  >    <img
>  > src="http://farm3.static.flickr.com/2146/buddyicons/24172116@N08.jpg?
>  > 12
>  > 03935044#24172116 at N08"
>  >         alt="Jolene_A" width="48" height="48" /><br />
>  >    Jolene_A
>  > </a>
>  >
>  > Notice the use of XFN: >>> rel="contact" <<<
>  >
>  > Metafilter also uses XFN.  Here is a sample page that uses XFN:
>  > http://www.metafilter.com/usercontacts/292
>  >
>  > Here's an example usage of XFN within that page:
>  >
>  > <a href="/user/10411" rel="colleague" target="_self">40 Watt</a>
>  >
>  > Notice the use of XFN: >>> rel="colleague" <<<
>  >
>  > Now, suppose that I wanted to create a spider application which crawls
>  > all social networks that use XFN.  Most likely, I would want the
>  > spider
>  > to collect:
>  >
>  > 1. Who is the source?  That is, who is the individual using XFN to
>  > state a relationship?
>  >
>  > 2. What is the relationship?  This is, of course, obtained easily from
>  > the value of the rel attribute on the link.
>  >
>  > 3. Who is the target?  That is, who is the other individual in the
>  > relationship?
>  >
>  > Examine the above snippets of code.  Does 1. and 3. pop out at you?
>  > That is, do you know who are the individuals that are the source and
>  > target of the relationship?
>  >
>  > That information "can" be found on the Flickr and Metafilter sites,
>  > but
>  > each site does it *differently*.
>  >
>  > So, the problem with XFN can be stated as this: While XFN does a great
>  > job of providing a set of relationship values (friend, contact,
>  > co-worker, etc), it provides no means for the automated discovery of
>  > the individuals that are the source and target of the relationship.
>  > Without information about the source and target individuals, the
>  > relationship information is not very useful.
>  >
>  > You might argue: "Well, the XFN *should* be embedded within an hCard,
>  > then you can discover who the source individual is.  And the target
>  > page should contain an hCard, then you can discover who the target
>  > individual is."  And I agree that is Best Practice.  Unfortunately,
>  > this is not mandated and consequently many people don't do it.  For
>  > example, Flickr and Metafilter don't do it.  Nor do any of the other
>  > social networks do it.
>  >
>  > Conversely, consider FOAF.  Advogato is a social network that uses
>  > FOAF.  Here an example FOAF on that network:
>  >
>  > http://www.advogato.org/person/connolly/foaf.rdf
>  >
>  > At the browser menu select View >> Page Source to see the actual FOAF
>  > document.  Notice that the individual who is the source of the
>  > relationship is clearly listed at the top of the document:
>  >
>  > <foaf:name>Dan Connolly</foaf:name>
>  >
>  > And the individual who is the target of the relationship is clearly
>  > identified:
>  >
>  >    <foaf:knows>
>  >      <foaf:Person
>  > rdf:about="http://www.advogato.org/person/jtauber/foaf.rdf#me">
>  >        <foaf:nick>jtauber</foaf:nick>
>  >        <rdfs:seeAlso
>  > rdf:resource="http://www.advogato.org/person/jtauber/foaf.rdf"/>
>  >      </foaf:Person>
>  >    </foaf:knows>
>  >
>  > The downside of FOAF is the only built-in relationship is "knows",
>  > e.g.
>  > "Dan Connolly knows James Tauber." That is, FOAF doesn't possess the
>  > richness of expression in terms of relationships. (I know, there are
>  > extensions of FOAF to express more than "knows," but as far as I can
>  > tell, no social network is using those extensions)
>  >
>  > The upside of FOAF is that all three pieces of information are
>  > available to a spider application:
>  >
>  > 1. The source individual (e.g. Dan Connolly)
>  >
>  > 2. The relationship ("knows")
>  >
>  > 3. The target individual (e.g. James Tauber)
>  >
>  > I don't see any solution to the problem with XFN.  As far as I can
>  > see,
>  > social networks using XFN cannot be processed by spiders.  Only social
>  > networks that use FOAF can be processed by spiders.  Bummer.
>  >
>  > Hopefully, I am missing something.  I really like the simplicity of
>  > XFN
>  > and its rich set of relationships.
>  >
>  > /Roger
>  >
>  >
>  >
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-- 
David Janes
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http://www.blogmatrix.com
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