Implementation of 3NN K-Nearest Neighbor clustering
as described in [1], to identify salient information as
the 2-degenerate cores from a clustering graph containing
information nodes that are linked to their 3-nearest neighbors,
and qualifying sentences that outrank previously selected
sentences using a relevance model of salient information seen
over a recent time interval.
[1] JBP Vuurens, AP de Vries, R Blanco, P Mika,
"Online News Tracking for Ad-Hoc Information Needs",
in ICTIR 2015.