TM::Tree - Topic Maps, trait for induced tree retrieval

  use TM::Materialized::AsTMa;
  my $tm = new TM::Materialized::AsTMa (file => 'old_testament.atm');
  Class::Trait->apply ( $tm => 'TM::Tree' );
  $tm->sync_in;

  # old-testament pedigree
  print Dumper $tm->tree (lid   => 'adam',
			  type  => 'has-parent',
			  arole => 'parent',
			  brole => 'child' );

  # new-testament inverse pedigree
  print Dumper $tm->tree (lid   => 'gw-bush',
			  type  => 'has-parent',
			  arole => 'child',
			  brole => 'parent' );

package TM::Tree;

use TM;

use Class::Trait 'base';

##our @REQUIRES  = qw(last_mod);

use Data::Dumper;

sub tree {
  my $self  = shift;
  my ($lid, $type, $arole, $brole) = $self->mids (shift, shift, shift, shift);
  my $depth = shift;

  return       _tree ($self,
		      $lid,
		      {},
		      [ $self->match_forall (type => $type) ],  # where are the associations which are relevant? (do not recompute them over and over, again)
		      $arole,
		      $brole,
		      0,                               # current depth
		      $depth);

sub _tree {
    my $self      = shift;
    my $lid       = shift;                                           # the current topic
    my $visited   = shift;                                           # a hash ref where we record what we have seen
    my $aids      = shift;                                           # list references to all maplets of that type
    my ($a, $b)   = (shift, shift);                                  # the roles
    my ($cd, $md) = (shift, shift);                                  # current depth, maxdepth

#warn "aids";#. Dumper $aids;

    return $visited->{$lid} if $visited->{$lid};                     # been there, done that

    my $n = {                                                        # we create a node for that topic
	      lid         => $lid,
	      children    => [],                                     # contains direct children
#	      'children*' => []                                      # contains also indirect one
	     };

    return $n if defined $md && $cd >= $md;

    foreach (grep ($self->is_x_player ($_, $lid, $a), @{$aids})) {  # shortcut OO method resolution
#warn "working on $_";
	foreach ($self->get_x_players ($_, $b)) {
#warn "    $_";
	    my $child = _tree ($self,
			       $_,
			       $visited,
			       $aids,
			       $a,
			       $b,
			       $cd+1,
			       $md);
	    push @{$n->{'children'}},  $child;
#	    push @{$n->{'children*'}}, $child->{lid}, @{$child->{'children*'}};
	}
    }

    $visited->{$n->{lid}} = $n;                                      # global hash which remembers already built subtrees
    return $n;
}

}


sub tree_x {
    my $self  = shift;
    my ($lid, $type, $arole, $brole) = (shift, shift, shift, shift);
    my $depth = shift;
    
    my @aids = $self->match_forall (type => $type);
    my $n = {                                                        # we create a node for that topic
	      lid         => $lid,
	      children    => [],                                     # contains direct children
#	      'children*' => []                                      # contains also indirect one
	     };
    return $n unless @aids;

    my $ai; # index for arole
    my $bi; # index for brole
    {                                             # figure out the static indices in one prototype assoc
	my $rs = $aids[0]->[TM->ROLES];           # we know that there must be at least one
	for (my $i = 0; $i < @$rs; $i++) {
	    if ($rs->[$i] eq $arole) {
		$ai = $i;
	    } elsif ($rs->[$i] eq $brole) {
		$bi = $i;
	    }
	}
    }
    my %arcs;
    foreach my $a (@aids) {
	my ($a, $b) = @{ $a->[TM->PLAYERS] }[$ai,$bi];
	push @{ $arcs{$a}}, $b;
    }
#warn Dumper \%arcs;
    return _tree_x (\%arcs, $lid, {}, 0, $depth);

sub _tree_x {
    my $arcs      = shift;
    my $lid       = shift;                                           # the current node
    my $visited   = shift;                                           # a hash ref where we record what we have seen
    my ($cd, $md) = (shift, shift);                                  # current depth, maxdepth
    return $visited->{$lid} if $visited->{$lid};                     # been there, done that
    my $n = {                                                        # we create a node for that topic
	      lid         => $lid,
	      children    => [],                                     # contains direct children
	     };
    return $n if defined $md && $cd >= $md;
    foreach my $ch (@{ $arcs->{$lid} }) {
	push @{$n->{'children'}}, _tree_x ($arcs, $ch, $visited, $cd+1, $md);
    }
    $visited->{$n->{lid}} = $n;                                      # global hash which remembers already built subtrees
}

}

sub taxonomy {
    my $self = shift;
    my $top  = shift || $self->mids ('thing');

    return $self->tree_x ($top, $self->mids ('is-subclass-of', 'superclass', 'subclass'));
}

our $VERSION  = 0.4;
our $REVISION = '$Id: Tree.pm,v 1.2 2006/12/01 08:01:00 rho Exp $';


1;

__END__

xxx=cut


computes a tree of topics based on a starting topic, an association type
and two roles. Whenever an association of the given type is found and the given topic appears in the
role given in this very association, then all topics appearing in the other given role are regarded to be
children in the result tree. There is also an optional C<depth> parameter. If it is not defined, no limit
applies. Starting from XTM::base version 0.34 loops are detected and are handled gracefully. The returned
tree might contain loops then.

Examples:


  $hierarchy = $tm->induced_assoc_tree (topic      => $start_node,
					assoc_type => 'at-relation',
					a_role     => 'tt-parent',
					b_role     => 'tt-child' );
  $yhcrareih = $tm->induced_assoc_tree (topic      => $start_node,
					assoc_type => 'at-relation',
					b_role     => 'tt-parent',
					a_role     => 'tt-child',
					depth      => 42 );

B<Note>


x=cut


x=pod