code: function Chart(N) {
    logger.debug("Chart: " + N);
    this.N = N;
    this.outgoing_edges = new Array(N+1);
    this.incoming_edges = new Array(N+1);
    
    var i;
    for (i = 0; i <= N; i++) {
      this.outgoing_edges[i] = {};
      this.incoming_edges[i] = {};
    }
    
  }
docs: Creates a chart for recognition of a sentence of length N