The Untyped Network Hypothesis is the representation of complex data structures in an untyped graph.
I'm developing Mneson http://www.liaad.up.pt/~maa/mneson/, a network database structure that implements this based on standard data structures (vectors, ordered sets, hash tables).
More soon.
See: http://www.liaad.up.pt/~maa/mneson/manual.html
See also: MultiParadigmDatabase, RdfTriples