柔性继承支撑系统ND—Polya的设计与实现

DESIGN AND IMPLEMENTATION OF ND POLYA LANGUAGE AND ITS SUPPORTING SYSTEM

继承是面向对象程序设计中的一个重要机制。但是，当程序员需要调整已有类并将其应用到类似的应用中，继承机制就不能支持这类程序员的需要。为了解决这一问题，我们结合类比和继承，提出了一种新的机制：柔性继承。该机制允许对类中属性进行删除和重定义。更重要的是，允许定义类之间的相似性，进行方法间的类比推导，实现对方法以及算法的复用。描述了对柔性继承的规约语言机制和推理系统有具体设计和实现。

Inheritance is a key mechanism in object oriented programming. However, it cannot meet the requirement of programmers to modify existing classes and reuse them in analogous applications. To solve this problem, we present a new mechanism, named Soft inheritance, which integrates analogy reasoning and inheritance. Our mechanism is capable of discarding and redefining attributes of class. The greatest significance of our mechanism is to define analogical specification between classes and makes analogical derivation of existing method, reusing the method and its algorithm. This paper is designed to depict our language facilities for analogical specification, and some important issues in the design and implementation of analogical derivation system, such as system structure, data structure and algorithms. Several important examples, including a graphics system, have been tested, which illustrated capabilities of our experimental mechanism. We argue that it is of much benefit to integrate analogy and inheritance to support reuse in programming.