setAllClassification = function(){
  	var inputElements = document.getElementById('checkboxes').getElementsByTagName('input');
  	for(input in inputElements){
  		inputElements[input].checked = '';
  	}
  	document.getElementById('_id_all').checked = 'true';
  }
  
  clearAllClassification = function(){
  	document.getElementById('_id_all').checked = '';
  }
  selectAllClassification = function(){
  	
  	var inputContainer = document.getElementById('checkboxes');
  	var inputElements = inputContainer.getElementsByTagName('input');
  	var hasChecked = false;
  	for(input in inputElements){
  		if(inputElements[input].checked){
  			hasChecked = true;
  		}
  	}
  	if(!hasChecked){
  		document.getElementById('_id_all').checked = 'true';
  	}
  }