A few links to related work, including Semantic Web (RDF, RSS, DC), Web of Trust (PGP etc) and the social networks literature.
Excerpt from the AmSci article 'Graph Theory in Practice':
Some of the most interesting large graphs are those in which we are the vertices. These social graphs are associated with the phrase "six degrees of separation," popularized by a 1990 play of that title and a later film, both written by John Guare. The idea is that the acquaintanceship graph connecting the entire human population has a diameter of six or less. Guare attributes this notion to Guglielmo Marconi, who supposedly said that wireless telegraphy would so contract the world that any two people could be linked by a chain of 5.83 intermediaries.
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