中文摘要：

不同于以整个文献的引用模式为知识系统骨架的研究思路，以知识系统中文献里的关键词为组元来建立共词网络是一个构造知识系统骨架和分析其演化的重要新手段。本文对共词网络的系统哲学和科学的基础进行了分析。以再生水为案例，建立起关键词的共词网络模型，以共词网络的构型演化和连接度分布等对知识系统的演化进行探讨。明确地揭示了共词网络是科学交流过程中形成的网络，知识系统具有自组织生成、构建和演化的基本规律。本文提出的共词网络方法和由其揭示的规律具有普适性，适合其它许多领域的知识系统的演化。本文的结果不仅在学术上有意义，在优化知识系统的对策和措施等具体应用中也有指导作用。

英文摘要：

Knowledge system （KS） is a self-organized complex system. To reveal its evolutionary law from the view of system philosophy/sciences , the essay gives associated assessment/action/measure. Different from taking citation pattern of whole literature as a skeleton of KS, to construct co-words network （CWN） by selecting keywords of KS as units is an important alternative avenue to construct the skeleton and analyze the evolution of KS. This paper analyzes system philosophical and scientific foundation of CWN. With reclaimed water as a case, CWN is proposed to analyze the evolution of CWN and degree dis- tribution for the evolution of KS. It clearly reveals that CWN is a network formed during the process of scientific communication, and synergetic KS gradually emerges, forms and evolves by self-organization,ly- ing at self-organized criticality. The CWN method and law are very universal,which can be used for the evolution of KS in many other fields. The results are not only importantly instructive in academy, but are helpful in specific engineering applications such as providing measures and actions of optimizing KS.