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

[Costello, Roger L.]

Thanks Ryan! "Representative hCard" -- nice!

In this message I will:

(a) Summarize purpose of the representative hCard.

(b) Check on the social networks that use XFN and see if they follow
the Representative hCard Best Practice.  

(c) Send out a plea to those social networks that aren't following the
Representative hCard Best Practice to do so.


PURPOSE OF THE REPRESENTATIVE HCARD

A web page may contain multiple hCards.  

For example, suppose Alice creates a web page.  Alice enjoys flying
airplanes, so in her web page she mentions the legendary aviator Chuck
Yeager, and creates an hCard for him (as well as for herself).  

So, in Alice's web page there are these two hCards:

<div class="vcard">
   <div class="fn">Alice Jones</div>
</div> 

<div class="vcard">
   <div class="fn">Chuck Yeager</div>
</div>

Additionally, in Alice's web page she has a link to the web page of her
friend Bob (who's also a flying aficionado):

<a href="http://www.example.org/Bob" rel="friend">Bob</a>

Note the use of XFN in the link:  >>> rel="friend <<<

Consider a robot that is trolling all the social networks that use XFN,
building a social network graph.  It arrives at Alice's web page, and
parses its way to the link to her friend Bob. Now the robot wants to
identify the source of this XFN "friend" relationship.  There are two
hCards on Alice's web page, how will the robot know which one
represents the source of the relationship?  That's the purpose of a
representative hCard!

The purpose of a representative hCard is to identify itself as "Hey,
look at me, I am the author of this page."

The way an hCard identifies itself as the representative hCard is by:

- add to link that points back to itself (the web page)
- on the link add the hCard properties url and uid

So here's how Alice redesigns her hCard:

<div class="vcard">
   <a href="http://www.example.org/Alice" class="url uid fn">Alice
Jones</a>
</div>  
 
Back to the robot ... it looks for the representative hCard and finds
it.  It now knows half of the relationship, i.e. Alice Jones is friends
with ???  To get the other half, the robot follows the link to Bob's
web page, finds the representative hCard on that web page, which is
this:

<div class="vcard">
   <a href="http://www.example.org/Bob" class="url uid fn">Bob
Smith</a>
</div>

Now the robot has all the information it needs:
  - the source is "Alice Jones"
  - the relationship is "friend"
  - the target is "Bob Smith"

That is, Alice Jones is friends with Bob Smith

The robot adds this to the social network graph that it's constructing,
and moves on to the next XFN-bearing link.  

TaDa!


ANALYSIS OF SOCIAL NETWORKS THAT USE XFN AND THEIR CONFORMANCE TO THE
REPRESENTATIVE HCARD BEST PRACTICE

Now, let's examine each of the social networks that use XFN to see if
they are following the Representative hCard Best Practice.

1. Flickr      http://www.flickr.com/people/tracylee/

Follow the Representative hCard Best Practice?  No.

2. Last.fm     http://www.last.fm/user/fbellintani/?scrobbling=t1

Follow the Representative hCard Best Practice?  No.

3. Ma.gnolia   http://ma.gnolia.com/people/apartness

Follow the Representative hCard Best Practice?  No.

4. MetaFilter  http://www.metafilter.com/usercontacts/292

Follow the Representative hCard Best Practice?  No. (doesn't have any
hCards)

5. Pownce      http://pownce.com/ariel/

Follow the Representative hCard Best Practice?  Yes!

6. Twitter     http://twitter.com/t

Follow the Representative hCard Best Practice?  No.


A PLEA TO INFLUENCE THE SOCIAL NETWORKS

Are there people on this list who can influence: 
  - Flickr, 
  - Last.fm, 
  - Ma.gnolia, 
  - MetaFilter, and 
  - Twitter 
to use a representative hCard to identify the person that the web page
is talking about?

/Roger