Theory and Methodology of Extended Object-Oriented Programming

针对使用继承的传统对象系统在映射真实世界的对象关系时遇到的各种困难，提出一种普遍的软件工程方法，即扩展的面向对象方法(XOO)，它通过支持双向派生、归纳、更一般的多态机制等技术，来补足继承机制的不足，并进一步增强对象方法在描述对象关系方面的能力.作者强调了虚归纳是一种普遍的软件工程方法，它使得归纳与继承的高效结合成为可能，可以作为重用已有类库代码和与继承类层次结合的有效方法.文中还描述了XOOP的一个较为完整的实现——编程语言C**.Some substantial difficulties can arise to traditional objectsystems when mapping the real world object relations. This paper presents XOO, as a universal software engineering methodology, to complement inheritance and overcome the difficulties. A special form of induction, called virtual induction, is a powerful mechanism for abstracting and reusing existing code and can be well blended with inheritance. A relatively thorough XOOP implementation, the programming language C**, is also discussed. A software technique (a programming language, an analysis or design method) is object-oriented if and only if it supports: (1) Data abstraction——providing some form of data abstraction and encapsulation (or information hiding), such as abstract data types or object classes; (2) Inheritance——providing the mechanism to derive new concrete abstractions out of the general abstractions (i.e., top-down feature propagation, including interface inheritance and implementation inheritance); (3) Behavior polymorphism——providing some form of dynamic binding based on inheritance, and this technique is of extended object-orientation if and only if it further supports: (4) Induction——the ability to build new general abstractions out of existing concrete ones by summing up their common features (i.e., bottom-up feature propagation, including interface induction and implementation induction); (5) Bi-directional derivation (BDD)——providing the ability to compose new abstractions out of existing ones by bottom-up and bi-directional feature propagation; (6) General polymorphism——the ability to provide dynamic binding based on induction and bi-directional derivation (besides inheritance). C**, designed in late 1990s, is yet another language along the way of general-purpose programming after C and C++. It adds the support for the new programming paradigm extended OOP to C++ while retaining full compatibility with C++. This paper presents the XOOP model of C**, as well as the explanation for C**'s XOOP fulfillment, with the emphasis on how it complements the classical OOP model by addressing a few typical problems that may cause substantial difficulties to existing OO technology. The paper further discusses C** language design, the inductive development approach, micro-kernel language structure, and a few typical implementation issues.国家自然科学基金; 国家重点基础研究发展计划(973计划)中文核心期刊要目总览(PKU)中国科学引文数据库(CSCD)03266-2802