The evolution of classification systems: Ontogeny of the UDC
  To classify is to put things in meaningful groups, but the criteria for doing so can be problematic. Study of evolution of classification includes ontogenetic analysis of change in classification over time. We present an empirical analysis of the UDC over the entire period of its development. We demonstrate stability in main classes, with major change driven by 20th century scientific developments. But we also demonstrate a vast increase in the complexity of auxiliaries. This study illustrates an alternative to Tennis' "scheme-versioning" method. 
Almila Akdag Salah, Cheng Gao, Krzysztof Suchecki, Andrea Scharnhorst,   Richard P. Smiraglia
cs.DL physics.soc-ph