This document is Cycom's illustrated gloss on a 1996 Draft International Standard ISO/DIS 12616.2. Readers are encouraged to buy the latest standard, (dated 2002, which includes an excellent annex giving example usage of data categories), direct from http://www.iso.ch/.
This document is best read via the "next" link at the base of each page and using your browsers "back" button when there is no "next" link. Not all pages are linked to this overview so you will miss some pages if you browse using the above links. The screenshots and illustrations were not present in the original cited documents.