Object-oriented programming inheritance

Similar to attributes, procedures can be inherited by child frames when inheritance is supported. Object-oriented programming enormously enlarges the flexibility of frame-based systems. A disadvantage is, however, that it results often in unclear and intractable reasoning structures. Table 43.2 shows the small rule base of Fig. 43.2, translated in an object-oriented system. 

Other, more advanced tools offer possibilities for combining different knowledge representations and inferencing strategies. They typically offer rules, combined with frames, different inheritance possibilities. The possibility of object-oriented programming is not always present. The user interface is not standardized and can be user tailored. The interface to standard packages is usually available. 

Encapsulation, inheritance, and polymorphism are the most well-known features of object-oriented programming. These features are provided by all object-oriented languages. 

One of the most important advantages of object-oriented programming is to facilitate the development of a new class that extends or modifies the features of the existing classes to adapt it to the demands of the specific problem. This feature is called inheritance. 

Ada 95 introduced direct support for object-oriented programming encapsulation (as just noted), objects (entities that have state and operations), classes (abstractions of objects), inheritance, polymorphism, and dynamic binding. 

Safety-critical developers rightly complain about the unsuitability of mainstream object-oriented programming languages for critical systems. The most widely used object-oriented programming language is C++, which inherits nearly all the problems of C and adds a few new ones such as ambiguous method calls. 

There are many benefits in defining superclasses. The amount of code that has to be written is reduced because the programmer is allowed to have subclasses inherit attributes and methods from superclasses. The program also reflects the depth of the current system model. Well-defined systems tend to have more subclasses and provide more reliable and accurate results than poorly defined systems. Although it may be possible to define the system in excruciating detail, it may not be necessary to do so from the outset. Object-oriented programming gives us the flexibility to define a system only coarsely and approximately at first, and refine it with incremental additions and modifications of classes and methods later on. 

In most current object-oriented programming languages, the possibility exists that a class of objects can inherit attributes from more than one superclass (multiple inheritance). 

Inheritance was initially touted as the preferred object-oriented way to achieve reuse and flexibility. In the early days of Smalltalk (one of the earliest popular OO programming languages), several papers were written promoting programming by adaptation. The principle was that you take someone else s code, make a subclass of it, and override whichever methods you require to work differently. Given, for example, a class that... 

---