**1. Introduction**

To regard the accurate evaluation of the effect of public diplomacy work as the most important research topic for public diplomacy scholars is not overstating the case. Clearly, unless we make an accurate assessment of past work, it will be difficult to determine whether or not current working ideas and methods are correct, whether or not certain policy proposals aimed at improving the effectiveness of public diplomacy will work, and in which public diplomacy areas or projects to increase investment in the future. In this sense, the empirical measurement and scientific evaluation of the effectiveness of 'public diplomacy'—a research area that is highly policy- and practice-related—should be the primary and most critical topic of research in this regard as a whole. However, to make an accurate assessment of public diplomacy, it is necessary to define theoretically its function, utility boundary and measurement method.

This chapter holds that public diplomacy's most important function is to transform a country's general assets into soft power resources, which refer to those assets that people of other countries like or support and which are therefore attractive to them. In other words, the function of public diplomacy is to reverse the attitude of people in other countries towards the assets (such as a certain culture, set of values or policies) of the implementing country from not knowing, liking or supporting them to the opposite. Therefore, the success of a public diplomacy effort is assessed according to whether or not it improves or enhances the public of target country's evaluation of a particular aspect of the implementing country.

However, owing to certain functional boundaries, public diplomacy does not work in all problem areas. In 'high-politics' such as territorial security, for instance, public diplomacy is likely to be of little use. But even in fields where public diplomacy can play a role, factors such as changes in power structure, differences in political systems and the quality of political relations among countries will still have impact on its effectiveness. The ultimate purpose of clarifying the function and functional boundaries of public diplomacy, therefore, is to measure more accurately its effect. This chapter further proposes that there are two main methods in this regard: one is the sampling survey method that is aimed at the general public, namely, the public opinion poll, and the other is that of the unstructured interview with a small specific group of people. Both methods have their advantages. As regards their practical application, however, certain matters demand attention.

This chapter is divided into four parts as follows. The first part discusses the definition and functions of public diplomacy on the basis of combing through and criticizing the existing viewpoints, thus to clarify the judgment criteria of the effect of public diplomacy. The second part discusses the functional boundaries of public diplomacy and points out the disturbance variables that affect its actual effect. On the basis of the first two parts, the third part discusses two empirical methods through which to measure the effect of public diplomacy and the problems to which attention should be paid in this regard. The fourth part is the conclusion.
