/// <summary>
		/// Adds a rule to the rule list.
		/// </summary>
		/// <param name="rule">
		/// A <see cref="SyntacticalRule"/>
		/// </param>
		private void AddRule(SyntacticalRule rule)
		{
			string [] parts = rule.ToString().Split(':');
			
			TreeIter iter = synRulesModel.AppendValues(parts[0]+" :",
			                                           parts[1],
			                                           rule);
			
			synRulesTree.Selection.SelectIter(iter);
			
			
			synRulesTree.ScrollToCell(synRulesModel.GetPath(iter), 
			                          synRulesTree.Columns[0],
			                          true,0.5f,0);
		}