Let's assume your customers requirements are 25 PPM. That means that you would be allowed 25 pieces for every 1,000,000 pieces or 250 defective parts per year. Or to put it another way, one bad part per day! Notice I did not say one bad part per day per person or job, or shift or machine.
The dynamic inheritance allows you to follow open-closed principle by extending classes without modifying existing classes and allows you to choose features that you need at runtime. Of course, dynamic languages such as Ruby make this a lot easier as you can extend classes or objects with modules at runtime, e.g.
Java - Inheritance. Inheritance can be defined as the process where one class acquires the properties (methods and fields) of another. With the use of inheritance the information is made manageable in a hierarchical order. The class which inherits the properties of other is known as subclass (derived class, child class) and the class whose properties are inherited is known as superclass (base class, parent class).