[uf-discuss] A (big) problem with XFN: identity of source and
target not findable
davidjanes at blogmatrix.com
Wed Mar 19 17:36:30 PST 2008
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. 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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