NAME

SeeAlso::Identifier::ISBN - International Standard Book Number Identifier

SYNOPSIS

  my $isbn = new SeeAlso::Identifier::ISBN "";

  print "invalid" unless $isbn; # $isbn is defined but false !

  $isbn->value( '0-8044-2957-x' );
  $isbn->value; # '' or ISBN-13 without hyphens (9780804429573)
  $isbn; # ISBN-13 as URI (urn:isbn:9780804429573)

  $isbn->hash; # long int between 0 and 1999999999 (or '')
  $isbn->hash( 59652724 ); # set by hash

  $isbn->canonical; # urn:isbn:9780596527242

DESCRIPTION

This module handles International Standard Book Numbers as identifiers. Unlike Business::ISBN the constructor of SeeAlso::Identifier::ISBN always returns an defined identifier with all methods provided by SeeAlso::Identifier. As canonical form the URN representation of ISBN-13 without hyphens is used - that means all ISBN-10 are converted to ISBN-13. As hashed form of an ISBN, a 32 Bit integer can be calculated.

Please note that '0' is a valid value representing ISBN-10 0-00-000000-0 and ISBN-13 978-0-00-000000-2 although it is mostly used errorously in practise.

METHODS

parse ( $value )

Get and/or set the value of the ISBN. Returns an empty string or the valid ISBN-13 without hyphens as determinded by Business::ISBN. You can also use this method as function.

canonical

Returns a Uniform Resource Identifier (URI) for this ISBN (or an empty string).

This is an URI according to RFC 3187 ("urn:isbn:..."). Unfortunately RFC 3187 is broken, because it does not oblige normalization - this method does: first only valid ISBN (with valid checkdigit) are allowed, second all ISBN are converted to ISBN-13 notation without hyphens (URIs without defined normalization and valitidy check are pointless).

Instead of RFC 3187 you could also use "http://purl.org/isbn/".

hash ( [ $value ] )

Returns or sets a space-efficient representation of the ISBN as long integer. An ISBN-13 always starts with '978' or '979' and ends with a check digit. This makes 2,000,000,000 possible ISBN which fits in a 32 bit (signed or unsigned) integer value. The integer value is calculated from the ISBN-13 by removing the check digit and subtracting 978,000,000,000.

AUTHOR

Jakob Voss <jakob.voss@gbv.de>

LICENSE

Copyright (C) 2007-2009 by Verbundzentrale Goettingen (VZG) and Jakob Voss

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.8.8 or, at your option, any later version of Perl 5 you may have available.