# 
# The contents of this file are subject to the Mozilla Public
# License Version 1.1 (the "License"); you may not use this file
# except in compliance with the License. You may obtain a copy of
# the License at http://www.mozilla.org/MPL/
# 
# Software distributed under the License is distributed on an "AS
# IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
# implied. See the License for the specific language governing
# rights and limitations under the License.
# 
# The Original Code is the RDF::Core module
# 
# The Initial Developer of the Original Code is Ginger Alliance Ltd.
# Portions created by Ginger Alliance are 
# Copyright (C) 2001 Ginger Alliance Ltd.
# All Rights Reserved.
# 
# Contributor(s):
# 
# Alternatively, the contents of this file may be used under the
# terms of the GNU General Public License Version 2 or later (the
# "GPL"), in which case the provisions of the GPL are applicable 
# instead of those above.  If you wish to allow use of your 
# version of this file only under the terms of the GPL and not to
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# GPL.
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package RDF::Core::Storage;

use strict;
require Exporter;

use Carp;

sub new {
    carp "Pure virtual function call.";
}
sub addStmt {
    carp "Pure virtual function call.";
}
sub removeStmt {
    carp "Pure virtual function call.";
}
sub existsStmt {
    carp "Pure virtual function call.";
}
sub getStmts {
    carp "Pure virtual function call.";
}
sub countStmts {
    carp "Pure virtual function call.";
}

1;
__END__

=head1 NAME

RDF::Core::Storage - An abstract ancestor of storage implementations

=head1 DESCRIPTION

Storage is the place where statements reside. It can add, remove, count and get statements and ask about their existence.

=head2 Interface

=over 4

=item * new(\%options)

Options depend on implementation of descendant. (Such as RDF::Core::Storage::Memory, RDF::Core::Storage::DB_File, RDF::Core::Storage::Postgres.)

=item * addStmt($statement)

Add RDF::Core::Statement instance to the storage, unless it already exists there.

=item * removeStmt($statement)

Remove statement from the storage, if it's there.

=item * existsStmt($subject,$predicate,$object)

Check if statement exists, that matches given mask. Parameters can be undefined, every value matches undefined parameter.

=item * countStmts($subject,$predicate,$object)

Count matching statements.

=item * getStmts($subject,$predicate,$object)

Retrieve matching statements. Returns RDF::Core::Enumerator object. (One of it's descendants.)

=back

=head1 LICENSE

This package is subject to the MPL (or the GPL alternatively).

=head1 AUTHOR

Ginger Alliance, rdf@gingerall.cz

=head1 SEE ALSO

RDF::Core::Storage::Memory, RDF::Core::Storage::DB_File, RDF::Core::Storage::Postgres

=cut