abstract class polygon {
    abstract function printCharacteristic();
  }

  class rectangle extends polygon {
    function printCharacteristic() {
      print("All my angles are 90 degrees and my opposite sides are equal");
    }
  }
  class square extends polygon {
    function printCharacteristic() {
      print("All my angles are 90 degrees and all my sides are equal");
    }
  }

  var shape1 : polygon = new rectangle;
  var shape2 : polygon = new square;

  shape1.printCharacteristics();
  shape2.printCharacteristics();

  All my angles are 90 degrees and my opposite sides are equal
  All my angles are 90 degrees and all my sides are equal

People who read this tip also read these tips:

• WSDL Example
• DOM Tree Representation of Entity References
• Creating IIS Web Server Virtual Directories
• Writing Web Forms
• Passing Objects to Behaviors