DDC 21 incorporates important changes and developments in the Dewey Decimal Classification that have occurred worldwide since the publication of DDC 20 in 1989. Important Changes in Edition 21. Three major revisions--350-354 Public administration, 370 Education, and 560-590 Life sciences-reflect new views and changes in the nature of the literature. The standard subdivision of Christianity have been relocated to reduce bias. Other adjustments reflect political and social changes, such as the major revision of Table 2--47 for the countries of the former Soviet Union. Topics that have gained literary warrant since the publication of Edition 20, e.g., rap music, virtual reality, and snowboarding, are included in this edition.