Peter Mika (MPF)
PhD Student at the Free University, Amsterdam, Netherlands (MPG)
See: http://www.cs.vu.nl/~pmika/ (MPH)
Refer to his recent work: "Ontologies are us: A unified model of social networks and semantics", ICSW 2005, Galway, Ireland - at: http://www.cs.vu.nl/~pmika/research/papers/ISWC-folksonomy.pdf (MPI)