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selected, false is not, or C<undef> if the item does not exist, or an error
occurs.

=head2 item $name

The C<item> method fetches and returns the item object, as specified by the
name argument.

Returns an L<Algorithm::Dependency::Item> object on success, or C<undef> if
an item does not exist for the argument provided.

=head2 depends $name1, ..., $nameN

Given a list of one or more item names, the C<depends> method will return
a reference to an array containing a list of the names of all the OTHER
items that also have to be selected to meet dependencies.

That is, if item A depends on B and C then the C<depends> method would
return a reference to an array with B and C. ( C<[ 'B', 'C' ]> )

If multiple item names are provided, the same applies. The list returned
will not contain duplicates.

The method returns a reference to an array of item names on success, a
reference to an empty array if no other items are needed, or C<undef>
on error.

NOTE: The result of C<depends> is ordered by an internal C<sort>
irrespective of the ordering provided by the dependency handler.  Use
L<Algorithm::Dependency::Ordered> and C<schedule> to use the most
common ordering (process sequence)

=head2 schedule $name1, ..., $nameN

Given a list of one or more item names, the C<depends> method will
return, as a reference to an array, the ordered list of items you
should act upon in whichever order this particular dependency handler
uses - see L<Algorithm::Dependency::Ordered> for one that implements
the most common ordering (process sequence).

This would be the original names provided, plus those added to satisfy
dependencies, in the preferred order of action. For the normal algorithm,
where order it not important, this is alphabetical order. This makes it
easier for someone watching a program operate on the items to determine
how far you are through the task and makes any logs easier to read.

If any of the names you provided in the arguments is already selected, it
will not be included in the list.

The method returns a reference to an array of item names on success, a
reference to an empty array if no items need to be acted upon, or C<undef>
on error.

=head2 schedule_all;

The C<schedule_all> method acts the same as the C<schedule> method, but 
returns a schedule that selected all the so-far unselected items.

=head1 TO DO

Add the C<check_source> method, to verify the integrity of the source.

Possibly add Algorithm::Dependency::Versions, to implement an ordered
dependency tree with versions, like for perl modules.

Currently readonly. Make the whole thing writable, so the module can be
used as the core of an actual dependency application, as opposed to just
being a tool.

=head1 SEE ALSO

L<Algorithm::Dependency::Ordered>, L<Algorithm::Dependency::Item>,
L<Algorithm::Dependency::Source>, L<Algorithm::Dependency::Source::File>

=head1 SUPPORT

Bugs may be submitted through L<the RT bug tracker|https://rt.cpan.org/Public/Dist/Display.html?Name=Algorithm-Dependency>
(or L<bug-Algorithm-Dependency@rt.cpan.org|mailto:bug-Algorithm-Dependency@rt.cpan.org>).

=head1 AUTHOR

Adam Kennedy <adamk@cpan.org>

=head1 CONTRIBUTORS

=for stopwords Adam Kennedy Karen Etheridge Mark Murawski

=over 4

=item *

Adam Kennedy <adam@ali.as>

=item *

Karen Etheridge <ether@cpan.org>

=item *

Mark Murawski <markm@intellasoft.net>

=back

=head1 COPYRIGHT AND LICENSE

This software is copyright (c) 2003 by Adam Kennedy.

This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.

=cut