The Subject Headings Authority File (German: Schlagwortnormdatei) or SWD is a controlled keyword descriptor system used primarily for subject indexing in library catalogs. The SWD is managed by the German National Library (DNB) in cooperation with various library networks. The inclusion of keywords in the SWD is defined by "Rules for the Keyword Catalogue" (RSWK). Similar authority systems in other languages include the Library of Congress Subject Headings (LCSH) and the Répertoire d'autorité-matière encyclopédique et alphabétique unifié (RAMEAU). Since April 2012 the SWD is part of the Integrated Authority File (Gemeinsame Normdatei or GND). The SWD has about 600,000 descriptors and 700,000 non-descriptors (synonyms and quasi-synonyms) as well as synonymous descriptor chains with references to a descriptor. Its growth rate is about 5.5% per year. About three-quarters of the descriptors refer to individual concepts (language identifier, person, entity, title, ethnography etc.) and a quarter are abstract concepts. Linking using hierarchical (about 115,000) and associative (26,000) relations is not very dense, so the SWD cannot be viewed as a thesaurus (as at mid-2003). The terms in the SWD are also arranged in a separate classification with nearly 500 classes in 36 main groups.