<para>

The <filename>isn</filename> module provides data types for the following

international product numbering standards: EAN13, UPC, ISBN (books), ISMN

(music), and ISSN (serials). Numbers are validated on input, and correctly

hyphenated on output.

(music), and ISSN (serials). Numbers are validated on input according to a

hard-coded list of prefixes; this list of prefixes is also used to hyphenate

numbers on output. Since new prefixes are assigned from time to time, the

list of prefixes may be out of date. It is hoped that a future version of

this module will obtained the prefix list from one or more tables that

can be easily updated by users as needed; however, at present, the

list can only be updated by modifying the source code and recompiling.

Alternatively, prefix validation and hyphenation support may be

dropped from a future version of this module.

</para>

<sect2>