Many library classification systems such as Dewey Decimal Classification are used for both subject searching in catalogs and for shelf arrangement. This reflects a clear dilemma because a system that is optimal for catalogs is probably not also optimal for shelf arrangement and vice versa.

Some libraries provide open shelves, others provide closed shelves. In open shelving may the way books are organized facilitate browsing and document retrieval. In libraries with closed shelving are often used principles which save space and provide simple retrieval, e.g. a combination of shelving by size/format and numerus currens order.

Mills (2004, p. 544-545): "Shelf order. This is scarcely ever mentioned in the literature on retrieval, being treated very much as a poor relation, if not a terminally ill one. This is most unfortunate, since it is the very first index to the resources of the library for the great majority of library users an in many cases the main or even only one".

Literature:

Mills, J. (2004). Faceted classification and logical division in information retrieval. Library Trends, 52(3), 541-570.

Laursen Vig, M. (1988). Åbne hylder før og nu. IN: Bøger, Biblioteker, Mennesker. Et Nordisk Festskrift tilegnet Torben Nielsen, Universitetsbiblioteket i København. Copenhagen: The Royal Library. (Pp. 199-212).