  This study analyzes the differences between the category structure of the
Universal Decimal Classification (UDC) system (which is one of the widely used
library classification systems in Europe) and Wikipedia. In particular, we
compare the emerging structure of category-links to the structure of classes in
the UDC. With this comparison we would like to scrutinize the question of how
do knowledge maps of the same domain differ when they are created socially
(i.e. Wikipedia) as opposed to when they are created formally (UDC) using
classificatio theory. As a case study, we focus on the category of "Arts".
