# UMLS::Similarity::lch.pm
#
# Module implementing the semantic relatedness measure described 
# by Leacock and Chodorow (1998).
#
<code>


sub getRelatedness
{
    my $self = shift;

    return undef if(!defined $self || !ref $self);

    my $concept1 = shift;
    my $concept2 = shift;

        #  get the interfaceg
    my $interface = $self->{'interface'};

    #  find the length of the shortest path
    #  if concept 1 and 2 are the same just return 1
    my $length = 0;
    if($concept1 eq $concept2) { $length = 1; }
    else { $length = $interface->findShortestPathLength($concept1, $concept2); }

    #  get the depth of the taxonomy
    my $depth = $interface->depth();
    
    #  if the length of hte path is less than zero return -1
    if($length < 0) { return -1; }

    #  calculate lch
    my $score = -1 * log ($length / (2 * $depth));
    
    return $score;

}


=