This volume records the majority of papers presented at the International UDC Seminar 2013 "Classi_cation & Visualization: Interfaces to Knowledge" that took place on 24-25 October in The Hague (The Netherlands). The programme of the Seminar featured twenty talks and a poster session. These proceedings contain seventeen full papers and two short poster papers, in the order in which they were placed in the programme. The programme contained a number...