[scpubgit/stemmatology.git] / base / lib / Text / Tradition / Parser / Self.pm

package Text::Tradition::Parser::Self;

use strict;
use warnings;
use Text::Tradition::Parser::GraphML qw/ graphml_parse /;
use TryCatch;

=head1 NAME

Text::Tradition::Parser::GraphML

=head1 SYNOPSIS

  use Text::Tradition;
  
  my $t_from_file = Text::Tradition->new( 
    'name' => 'my text',
    'input' => 'Self',
    'file' => '/path/to/tradition.xml'
    );
    
  my $t_from_string = Text::Tradition->new( 
    'name' => 'my text',
    'input' => 'Self',
    'string' => $tradition_xml,
    );

=head1 DESCRIPTION

Parser module for Text::Tradition to read in its own GraphML output format.
GraphML is a relatively simple graph description language; a 'graph' element
can have 'node' and 'edge' elements, and each of these can have simple 'data'
elements for attributes to be saved.

The graph itself has attributes as in the Collation object:

=over

=item * linear 

=item * ac_label

=item * baselabel

=item * wit_list_separator

=back

The node objects have the following attributes:

=over

=item * name

=item * reading

=item * identical

=item * rank

=item * class

=back

The edge objects have the following attributes:

=over

=item * class

=item * witness (for 'path' class edges)

=item * extra   (for 'path' class edges)

=item * relationship    (for 'relationship' class edges)

=item * equal_rank      (for 'relationship' class edges)

=item * non_correctable (for 'relationship' class edges)

=item * non_independent (for 'relationship' class edges)

=back

=head1 METHODS

=head2 B<parse>

parse( $graph, $opts );

Takes an initialized Text::Tradition object and a set of options; creates
the appropriate nodes and edges on the graph.  The options hash should
include either a 'file' argument or a 'string' argument, depending on the
source of the XML to be parsed.

=begin testing

use Safe::Isa;
use Test::Warn;
use Text::Tradition;
use TryCatch;
binmode STDOUT, ":utf8";
binmode STDERR, ":utf8";
eval { no warnings; binmode $DB::OUT, ":utf8"; };

my $tradition = 't/data/florilegium_graphml.xml';
my $t = Text::Tradition->new( 
    'name'  => 'inline', 
    'input' => 'Self',
    'file'  => $tradition,
    );

ok( $t->$_isa('Text::Tradition'), "Parsed GraphML version 2" );
if( $t ) {
    is( scalar $t->collation->readings, 319, "Collation has all readings" );
    is( scalar $t->collation->paths, 376, "Collation has all paths" );
    is( scalar $t->witnesses, 13, "Collation has all witnesses" );
}

# TODO add a relationship, add a stemma, write graphml, reparse it, check that 
# the new data is there
my $language_enabled = $t->can('language');
if( $language_enabled ) {
	$t->language('Greek');
}
my $stemma_enabled = $t->can('add_stemma');
if( $stemma_enabled ) {
	$t->add_stemma( 'dotfile' => 't/data/florilegium.dot' );
}
$t->collation->add_relationship( 'w12', 'w13', 
	{ 'type' => 'grammatical', 'scope' => 'global', 
	  'annotation' => 'This is some note' } );
ok( $t->collation->get_relationship( 'w12', 'w13' ), "Relationship set" );
my $graphml_str = $t->collation->as_graphml;

my $newt = Text::Tradition->new( 'input' => 'Self', 'string' => $graphml_str );
ok( $newt->$_isa('Text::Tradition'), "Parsed current GraphML version" );
if( $newt ) {
    is( scalar $newt->collation->readings, 319, "Collation has all readings" );
    is( scalar $newt->collation->paths, 376, "Collation has all paths" );
    is( scalar $newt->witnesses, 13, "Collation has all witnesses" );
    is( scalar $newt->collation->relationships, 1, "Collation has added relationship" );
    if( $language_enabled ) {
	    is( $newt->language, 'Greek', "Tradition has correct language setting" );
	}
    my $rel = $newt->collation->get_relationship( 'w12', 'w13' );
    ok( $rel, "Found set relationship" );
    is( $rel->annotation, 'This is some note', "Relationship has its properties" );
    if( $stemma_enabled ) {
	    is( scalar $newt->stemmata, 1, "Tradition has its stemma" );
    	is( $newt->stemma(0)->witnesses, $t->stemma(0)->witnesses, "Stemma has correct length witness list" );
    }
}

# Test warning if we can
unless( $stemma_enabled ) {
	my $nst;
	warnings_exist {
		$nst = Text::Tradition->new( 'input' => 'Self', 'file' => 't/data/lexformat.xml' );
	} [qr/DROPPING stemmata/],
		"Got expected stemma drop warning on parse";
}

=end testing

=cut
use Data::Dump;
sub parse {
    my( $tradition, $opts ) = @_;
    
    # Collation data is in the first graph; relationship-specific stuff 
    # is in the second.
    my( $graph_data, $rel_data ) = graphml_parse( $opts );

    my $collation = $tradition->collation;
    my %witnesses;
    
    # print STDERR "Setting graph globals\n";
    $tradition->name( $graph_data->{'name'} );

    my $use_version;
    my $tmeta = $tradition->meta;
    my $cmeta = $collation->meta;
    foreach my $gkey ( keys %{$graph_data->{'global'}} ) {
		my $val = $graph_data->{'global'}->{$gkey};
		if( $gkey eq 'version' ) {
			$use_version = $val;
		} elsif( $gkey eq 'stemmata' ) {
			# Make sure we can handle stemmata
			# Parse the stemmata into objects
			if( $tradition->can('add_stemma') ) {
				foreach my $dotstr ( split( /\n/, $val ) ) {
					$tradition->add_stemma( 'dot' => $dotstr );
				}
			} else {
				warn "Analysis module not installed; DROPPING stemmata";
			}
		} elsif( $gkey eq 'language' ) {
			if( $tradition->can('language') ) {
				$tradition->language( $val );
			} else {
				warn "Morphology module not installed; DROPPING language";
			}
		} elsif( $gkey eq 'user' ) {
			# Assign the tradition to the user if we can
			if( exists $opts->{'userstore'} ) {
				my $userdir = delete $opts->{'userstore'};
				my $user = $userdir->find_user( { username => $val } );
				if( $user ) {
					$user->add_tradition( $tradition );
				} else {
					warn( "Found no user with ID $val; DROPPING user assignment" );
				}
			} else {
				warn( "DROPPING user assignment without a specified userstore" );
			}
		} elsif( $tmeta->has_attribute( $gkey ) ) {
			$tradition->$gkey( $val );
		} else {
			$collation->$gkey( $val );
		}
	}
		
    # Add the nodes to the graph.
    # Note any reading IDs that were changed in order to comply with XML 
    # name restrictions; we have to hardcode start & end.
    my %namechange = ( '#START#' => '__START__', '#END#' => '__END__' );

    # print STDERR "Adding collation readings\n";
    foreach my $n ( @{$graph_data->{'nodes'}} ) {    	
    	# If it is the start or end node, we already have one, so
    	# grab the rank and go.
        if( defined $n->{'is_start'} ) {
			$collation->start->rank($n->{'rank'});
			next;
        }
    	if( defined $n->{'is_end'} ) {
    		$collation->end->rank( $n->{'rank'} );
    		next;
    	}
		my $gnode = $collation->add_reading( $n );
		if( $gnode->id ne $n->{'id'} ) {
			$namechange{$n->{'id'}} = $gnode->id;
		}
    }
        
    # Now add the edges.
    # print STDERR "Adding collation path edges\n";
    foreach my $e ( @{$graph_data->{'edges'}} ) {
    	my $sourceid = exists $namechange{$e->{'source'}->{'id'}}
    		? $namechange{$e->{'source'}->{'id'}} : $e->{'source'}->{'id'};
    	my $targetid = exists $namechange{$e->{'target'}->{'id'}}
    		? $namechange{$e->{'target'}->{'id'}} : $e->{'target'}->{'id'};
        my $from = $collation->reading( $sourceid );
        my $to = $collation->reading( $targetid );

		warn "No witness label on path edge!" unless $e->{'witness'};
		my $label = $e->{'witness'} . ( $e->{'extra'} ? $collation->ac_label : '' );
		$collation->add_path( $from, $to, $label );
		
		# Add the witness if we don't have it already.
		unless( $witnesses{$e->{'witness'}} ) {
			$tradition->add_witness( 
				sigil => $e->{'witness'}, 'sourcetype' => 'collation' );
			$witnesses{$e->{'witness'}} = 1;
		}
		$tradition->witness( $e->{'witness'} )->is_layered( 1 ) if $e->{'extra'};
    }
    
    ## Done with the main graph, now look at the relationships.
	# Nodes are added via the call to add_reading above.  We only need
	# add the relationships themselves.
	# TODO check that scoping does trt
	$rel_data->{'edges'} ||= []; # so that the next line doesn't break on no rels
	foreach my $e ( sort { _layersort_rel( $a, $b ) } @{$rel_data->{'edges'}} ) {
    	my $sourceid = exists $namechange{$e->{'source'}->{'id'}}
    		? $namechange{$e->{'source'}->{'id'}} : $e->{'source'}->{'id'};
    	my $targetid = exists $namechange{$e->{'target'}->{'id'}}
    		? $namechange{$e->{'target'}->{'id'}} : $e->{'target'}->{'id'};
        my $from = $collation->reading( $sourceid );
        my $to = $collation->reading( $targetid );
		delete $e->{'source'};
		delete $e->{'target'};
		# The remaining keys are relationship attributes.
		# Backward compatibility...
		if( $use_version eq '2.0' || $use_version eq '3.0' ) {
			delete $e->{'class'};
			$e->{'type'} = delete $e->{'relationship'} if exists $e->{'relationship'};
		}
		# Add the specified relationship unless we already have done.
		my $rel_exists;
		if( $e->{'scope'} ne 'local' ) {
			my $relobj = $collation->get_relationship( $from, $to );
			if( $relobj && $relobj->scope eq $e->{'scope'}
				&& $relobj->type eq $e->{'type'} ) {
				$rel_exists = 1;
			}
		}
		try {
			$collation->add_relationship( $from, $to, $e ) unless $rel_exists;
		} catch( Text::Tradition::Error $e ) {
			warn "DROPPING $from -> $to: " . $e->message;
		}
	}
	
    # Save the text for each witness so that we can ensure consistency
    # later on
	$collation->text_from_paths();	
}

## Return the relationship that comes first in priority.
my %LAYERS = (
	'collated' => 1,
	'orthographic' => 2,
	'spelling' => 3,
	);

sub _layersort_rel {
	my( $a, $b ) = @_;
	my $key = exists $a->{'type'} ? 'type' : 'relationship';
	my $at = $LAYERS{$a->{$key}} || 99;
	my $bt = $LAYERS{$b->{$key}} || 99;
	return $at <=> $bt;
}

1;

=head1 BUGS / TODO

=over

=item * Make this into a stream parser with GraphML

=item * Simply field -> attribute correspondence for nodes and edges

=item * Share key name constants with Collation.pm

=back

=head1 LICENSE

This package is free software and is provided "as is" without express
or implied warranty.  You can redistribute it and/or modify it under
the same terms as Perl itself.

=head1 AUTHOR

Tara L Andrews E<lt>aurum@cpan.orgE<gt>
Commit	Line	Data
32014ec9	1	package Text::Tradition::Parser::Self;
	2
	3	use strict;
	4	use warnings;
1f7aa795	5	use Text::Tradition::Parser::GraphML qw/ graphml_parse /;
00c5bf0b	6	use TryCatch;
32014ec9	7
	8	=head1 NAME
	9
	10	Text::Tradition::Parser::GraphML
	11
e867486f	12	=head1 SYNOPSIS
	13
	14	use Text::Tradition;
	15
	16	my $t_from_file = Text::Tradition->new(
	17	'name' => 'my text',
	18	'input' => 'Self',
	19	'file' => '/path/to/tradition.xml'
	20	);
	21
	22	my $t_from_string = Text::Tradition->new(
	23	'name' => 'my text',
	24	'input' => 'Self',
	25	'string' => $tradition_xml,
	26	);
	27
32014ec9	28	=head1 DESCRIPTION
	29
	30	Parser module for Text::Tradition to read in its own GraphML output format.
e867486f	31	GraphML is a relatively simple graph description language; a 'graph' element
	32	can have 'node' and 'edge' elements, and each of these can have simple 'data'
	33	elements for attributes to be saved.
32014ec9	34
e867486f	35	The graph itself has attributes as in the Collation object:
	36
	37	=over
	38
	39	=item * linear
	40
	41	=item * ac_label
	42
	43	=item * baselabel
	44
	45	=item * wit_list_separator
	46
	47	=back
	48
	49	The node objects have the following attributes:
32014ec9	50
	51	=over
	52
e867486f	53	=item * name
	54
	55	=item * reading
	56
	57	=item * identical
	58
	59	=item * rank
	60
	61	=item * class
	62
	63	=back
	64
	65	The edge objects have the following attributes:
	66
	67	=over
	68
	69	=item * class
	70
	71	=item * witness (for 'path' class edges)
	72
	73	=item * extra (for 'path' class edges)
	74
	75	=item * relationship (for 'relationship' class edges)
	76
	77	=item * equal_rank (for 'relationship' class edges)
32014ec9	78
e867486f	79	=item * non_correctable (for 'relationship' class edges)
32014ec9	80
e867486f	81	=item * non_independent (for 'relationship' class edges)
	82
	83	=back
	84
	85	=head1 METHODS
	86
	87	=head2 B<parse>
	88
	89	parse( $graph, $opts );
	90
	91	Takes an initialized Text::Tradition object and a set of options; creates
	92	the appropriate nodes and edges on the graph. The options hash should
	93	include either a 'file' argument or a 'string' argument, depending on the
	94	source of the XML to be parsed.
	95
	96	=begin testing
	97
951ddfe8	98	use Safe::Isa;
9fef629b	99	use Test::Warn;
e867486f	100	use Text::Tradition;
951ddfe8	101	use TryCatch;
e867486f	102	binmode STDOUT, ":utf8";
	103	binmode STDERR, ":utf8";
	104	eval { no warnings; binmode $DB::OUT, ":utf8"; };
	105
	106	my $tradition = 't/data/florilegium_graphml.xml';
	107	my $t = Text::Tradition->new(
	108	'name' => 'inline',
	109	'input' => 'Self',
	110	'file' => $tradition,
	111	);
	112
951ddfe8	113	ok( $t->$_isa('Text::Tradition'), "Parsed GraphML version 2" );
e867486f	114	if( $t ) {
e867486f	115	is( scalar $t->collation->readings, 319, "Collation has all readings" );
255875b8	116	is( scalar $t->collation->paths, 376, "Collation has all paths" );
e867486f	117	is( scalar $t->witnesses, 13, "Collation has all witnesses" );
	118	}
	119
2a812726	120	# TODO add a relationship, add a stemma, write graphml, reparse it, check that
2a812726	121	# the new data is there
e92d4229	122	my $language_enabled = $t->can('language');
	123	if( $language_enabled ) {
	124	$t->language('Greek');
	125	}
37bf09f4	126	my $stemma_enabled = $t->can('add_stemma');
951ddfe8	127	if( $stemma_enabled ) {
	128	$t->add_stemma( 'dotfile' => 't/data/florilegium.dot' );
	129	}
bbd064a9	130	$t->collation->add_relationship( 'w12', 'w13',
	131	{ 'type' => 'grammatical', 'scope' => 'global',
	132	'annotation' => 'This is some note' } );
	133	ok( $t->collation->get_relationship( 'w12', 'w13' ), "Relationship set" );
	134	my $graphml_str = $t->collation->as_graphml;
	135
	136	my $newt = Text::Tradition->new( 'input' => 'Self', 'string' => $graphml_str );
951ddfe8	137	ok( $newt->$_isa('Text::Tradition'), "Parsed current GraphML version" );
bbd064a9	138	if( $newt ) {
	139	is( scalar $newt->collation->readings, 319, "Collation has all readings" );
	140	is( scalar $newt->collation->paths, 376, "Collation has all paths" );
	141	is( scalar $newt->witnesses, 13, "Collation has all witnesses" );
	142	is( scalar $newt->collation->relationships, 1, "Collation has added relationship" );
e92d4229	143	if( $language_enabled ) {
	144	is( $newt->language, 'Greek', "Tradition has correct language setting" );
	145	}
bbd064a9	146	my $rel = $newt->collation->get_relationship( 'w12', 'w13' );
	147	ok( $rel, "Found set relationship" );
	148	is( $rel->annotation, 'This is some note', "Relationship has its properties" );
951ddfe8	149	if( $stemma_enabled ) {
	150	is( scalar $newt->stemmata, 1, "Tradition has its stemma" );
	151	is( $newt->stemma(0)->witnesses, $t->stemma(0)->witnesses, "Stemma has correct length witness list" );
	152	}
bbd064a9	153	}
bbd064a9	154
951ddfe8	155	# Test warning if we can
	156	unless( $stemma_enabled ) {
	157	my $nst;
	158	warnings_exist {
	159	$nst = Text::Tradition->new( 'input' => 'Self', 'file' => 't/data/lexformat.xml' );
	160	} [qr/DROPPING stemmata/],
	161	"Got expected stemma drop warning on parse";
	162	}
bbd064a9	163
e867486f	164	=end testing
32014ec9	165
32014ec9	166	=cut
144d845b	167	use Data::Dump;
32014ec9	168	sub parse {
dfc37e38	169	my( $tradition, $opts ) = @_;
2626f709	170
	171	# Collation data is in the first graph; relationship-specific stuff
	172	# is in the second.
	173	my( $graph_data, $rel_data ) = graphml_parse( $opts );
144d845b	174
32014ec9	175	my $collation = $tradition->collation;
32014ec9	176	my %witnesses;
e309421a	177
0068967c	178	# print STDERR "Setting graph globals\n";
e3196b2a	179	$tradition->name( $graph_data->{'name'} );
144d845b	180
2626f709	181	my $use_version;
bbd064a9	182	my $tmeta = $tradition->meta;
bbd064a9	183	my $cmeta = $collation->meta;
255875b8	184	foreach my $gkey ( keys %{$graph_data->{'global'}} ) {
	185	my $val = $graph_data->{'global'}->{$gkey};
	186	if( $gkey eq 'version' ) {
	187	$use_version = $val;
9fef629b	188	} elsif( $gkey eq 'stemmata' ) {
951ddfe8	189	# Make sure we can handle stemmata
9fef629b	190	# Parse the stemmata into objects
37bf09f4	191	if( $tradition->can('add_stemma') ) {
951ddfe8	192	foreach my $dotstr ( split( /\n/, $val ) ) {
	193	$tradition->add_stemma( 'dot' => $dotstr );
	194	}
37bf09f4	195	} else {
37bf09f4	196	warn "Analysis module not installed; DROPPING stemmata";
2a812726	197	}
e92d4229	198	} elsif( $gkey eq 'language' ) {
	199	if( $tradition->can('language') ) {
	200	$tradition->language( $val );
	201	} else {
	202	warn "Morphology module not installed; DROPPING language";
	203	}
9fef629b	204	} elsif( $gkey eq 'user' ) {
	205	# Assign the tradition to the user if we can
	206	if( exists $opts->{'userstore'} ) {
1df4baa9	207	my $userdir = delete $opts->{'userstore'};
9fef629b	208	my $user = $userdir->find_user( { username => $val } );
	209	if( $user ) {
	210	$user->add_tradition( $tradition );
	211	} else {
	212	warn( "Found no user with ID $val; DROPPING user assignment" );
	213	}
	214	} else {
	215	warn( "DROPPING user assignment without a specified userstore" );
	216	}
bbd064a9	217	} elsif( $tmeta->has_attribute( $gkey ) ) {
bbd064a9	218	$tradition->$gkey( $val );
255875b8	219	} else {
	220	$collation->$gkey( $val );
	221	}
	222	}
e309421a	223
10e4b1ac	224	# Add the nodes to the graph.
	225	# Note any reading IDs that were changed in order to comply with XML
	226	# name restrictions; we have to hardcode start & end.
	227	my %namechange = ( '#START#' => '__START__', '#END#' => '__END__' );
32014ec9	228
bbd064a9	229	# print STDERR "Adding collation readings\n";
2626f709	230	foreach my $n ( @{$graph_data->{'nodes'}} ) {
0174d6a9	231	# If it is the start or end node, we already have one, so
0174d6a9	232	# grab the rank and go.
144d845b	233	if( defined $n->{'is_start'} ) {
a445ce40	234	$collation->start->rank($n->{'rank'});
a445ce40	235	next;
144d845b	236	}
bbd064a9	237	if( defined $n->{'is_end'} ) {
bbd064a9	238	$collation->end->rank( $n->{'rank'} );
0174d6a9	239	next;
0174d6a9	240	}
bbd064a9	241	my $gnode = $collation->add_reading( $n );
10e4b1ac	242	if( $gnode->id ne $n->{'id'} ) {
	243	$namechange{$n->{'id'}} = $gnode->id;
	244	}
32014ec9	245	}
910a0a6d	246
32014ec9	247	# Now add the edges.
bbd064a9	248	# print STDERR "Adding collation path edges\n";
32014ec9	249	foreach my $e ( @{$graph_data->{'edges'}} ) {
10e4b1ac	250	my $sourceid = exists $namechange{$e->{'source'}->{'id'}}
	251	? $namechange{$e->{'source'}->{'id'}} : $e->{'source'}->{'id'};
	252	my $targetid = exists $namechange{$e->{'target'}->{'id'}}
	253	? $namechange{$e->{'target'}->{'id'}} : $e->{'target'}->{'id'};
	254	my $from = $collation->reading( $sourceid );
	255	my $to = $collation->reading( $targetid );
bbd064a9	256
	257	warn "No witness label on path edge!" unless $e->{'witness'};
	258	my $label = $e->{'witness'} . ( $e->{'extra'} ? $collation->ac_label : '' );
	259	$collation->add_path( $from, $to, $label );
	260
2626f709	261	# Add the witness if we don't have it already.
bbd064a9	262	unless( $witnesses{$e->{'witness'}} ) {
82fa4d57	263	$tradition->add_witness(
82fa4d57	264	sigil => $e->{'witness'}, 'sourcetype' => 'collation' );
bbd064a9	265	$witnesses{$e->{'witness'}} = 1;
255875b8	266	}
bbd064a9	267	$tradition->witness( $e->{'witness'} )->is_layered( 1 ) if $e->{'extra'};
32014ec9	268	}
2626f709	269
	270	## Done with the main graph, now look at the relationships.
	271	# Nodes are added via the call to add_reading above. We only need
	272	# add the relationships themselves.
	273	# TODO check that scoping does trt
bf6e338d	274	$rel_data->{'edges'} \|\|= []; # so that the next line doesn't break on no rels
bf6e338d	275	foreach my $e ( sort { _layersort_rel( $a, $b ) } @{$rel_data->{'edges'}} ) {
10e4b1ac	276	my $sourceid = exists $namechange{$e->{'source'}->{'id'}}
	277	? $namechange{$e->{'source'}->{'id'}} : $e->{'source'}->{'id'};
	278	my $targetid = exists $namechange{$e->{'target'}->{'id'}}
	279	? $namechange{$e->{'target'}->{'id'}} : $e->{'target'}->{'id'};
	280	my $from = $collation->reading( $sourceid );
	281	my $to = $collation->reading( $targetid );
bbd064a9	282	delete $e->{'source'};
	283	delete $e->{'target'};
	284	# The remaining keys are relationship attributes.
	285	# Backward compatibility...
	286	if( $use_version eq '2.0' \|\| $use_version eq '3.0' ) {
	287	delete $e->{'class'};
	288	$e->{'type'} = delete $e->{'relationship'} if exists $e->{'relationship'};
	289	}
	290	# Add the specified relationship unless we already have done.
fdfa59a7	291	my $rel_exists;
bbd064a9	292	if( $e->{'scope'} ne 'local' ) {
	293	my $relobj = $collation->get_relationship( $from, $to );
	294	if( $relobj && $relobj->scope eq $e->{'scope'}
	295	&& $relobj->type eq $e->{'type'} ) {
fdfa59a7	296	$rel_exists = 1;
	297	}
	298	}
00c5bf0b	299	try {
	300	$collation->add_relationship( $from, $to, $e ) unless $rel_exists;
	301	} catch( Text::Tradition::Error $e ) {
	302	warn "DROPPING $from -> $to: " . $e->message;
	303	}
2626f709	304	}
861c3e27	305
	306	# Save the text for each witness so that we can ensure consistency
	307	# later on
bbd064a9	308	$collation->text_from_paths();
32014ec9	309	}
32014ec9	310
bf6e338d	311	## Return the relationship that comes first in priority.
	312	my %LAYERS = (
	313	'collated' => 1,
	314	'orthographic' => 2,
	315	'spelling' => 3,
	316	);
	317
	318	sub _layersort_rel {
	319	my( $a, $b ) = @_;
	320	my $key = exists $a->{'type'} ? 'type' : 'relationship';
	321	my $at = $LAYERS{$a->{$key}} \|\| 99;
	322	my $bt = $LAYERS{$b->{$key}} \|\| 99;
	323	return $at <=> $bt;
	324	}
	325
e867486f	326	1;
	327
	328	=head1 BUGS / TODO
	329
	330	=over
	331
	332	=item * Make this into a stream parser with GraphML
	333
	334	=item * Simply field -> attribute correspondence for nodes and edges
	335
	336	=item * Share key name constants with Collation.pm
	337
32014ec9	338	=back
	339
	340	=head1 LICENSE
	341
	342	This package is free software and is provided "as is" without express
	343	or implied warranty. You can redistribute it and/or modify it under
	344	the same terms as Perl itself.
	345
	346	=head1 AUTHOR
	347
e867486f	348	Tara L Andrews E<lt>aurum@cpan.orgE<gt>