A 3-D distortion-invariant multi-class object identification problem is addressed. Our new, fast and robust string-code generation technique (using optical and digital methods) makes the rule-based system quite practical and attractive. Emphasis is given to our rule-based system and to initial data results. Excellent multi-class recognition and reasonable object distortions can be accommodated in this system. We achieved 80-90% correct recognition (PC) for 10 object classes and ±30° 3-D distortions and full 360° in-plane distortions.