code: function DoubleDottedItem(parameters) {
    // An identifier is constructed from rule, dots, from and to
    this.id = "DoubleDottedItem(" + parameters.rule.lhs + "->" + 
      parameters.rule.rhs + ", " + parameters.left_dot + ", " + 
      parameters.right_dot + ", " + parameters.from + ", " + parameters.to +")";
    logger.debug("Enter DoubleDottedItem: " + this.id);
    this.name = parameters.rule.lhs;
    this.children = [];
  
    this.data = {};
    this.data.rule = parameters.rule;
    this.data.left_dot = parameters.left_dot;
    this.data.right_dot = parameters.right_dot;
    this.data.from = parameters.from;
    this.data.to = parameters.to;
    this.data.fs = parameters.fs;
    logger.debug("Exit DoubleDottedItem: created item: " + this.id);
  }
docs: Creates a doubledotted item; left_dot is an index in the RHS of the rule as well as right_dot from is the starting point in the sentence Data structure is prepared for use with InfoVis