It is worth noting that the number of classes chosen for the
shelf display will influence the length of the book numbers. If there
are fewer classes, the class mark will be short but the book mark
will have to be longer to accommodate a larger number of
documents. Here again one can note a slight difference in practice
between Anglo-American in which classification is used mainly for
shelf arrangement and European libraries which often have detailed
systematic catalogues allowing users to search and browse a subject
classification to a very fine detail. Class marks used on a shelf in
European libraries generally aim towards maintaining a ‘coarser’
grouping of subjects. The assumption is that users having specific
information needs will search the catalogue. Those who are
uncertain as to what they are looking for will browse shelves and
thus need not be distracted by the fine class subdivision.
Some guidelines suggest that a class on the shelf may have
up to 50 titles.
This is very different from Anglo-American practice which
applies classification (e.g. Dewey) to the greatest possible detail,
thus forming classes on the shelf that may contain as little as one
or two titles.