In this study, the topic model was applied to specify the topics of the discussions in community disaster risk management workshops in Kunigami village, Okinawa, Japan. 20 topics were extracted from the text data of the workshop discussions held at 8 communities in the village. Not only the issues on natural hazards, but also the issues on local factors and mitigation activities were specified.

The role of small-group discussion in disaster risk management is to create concrete and practical plans that include regional information. A facilitator is required to encourage residents to reveal such regional information through discussion. However, it is unclear how the facilitator contributes to a fruitful discussion. This study is designed to identify the topics discussed by residents in small-group discussions and, using text mining methodology, to evaluate the regionality of these topics. Our method is useful for evaluating whether a facilitator guided participants to discuss topics with high regionality and generality during the phases of developing and summarizing the discussion, respectively.

In this study, the hypothesis on the decision making on the residential choice with slope disaster risk was tested. First, two types of decisions, moving-in and moving-out decisions, were defined. Then, the hypothesis that people in moving-in decision are more risk averse than in moving-out decision was set. In order to test the hypothesis, the web survey was conducted and the difference of the equivalent rents was confirmed. Then, the hypothesis was verified. The results of the survey were interpreted by using prospect theory.

Management of planning process is necessary to adopt participants' opinions to alternatives in participatory planning process in a community. In the management, reconstruction of the discussion is important for planners and participants to share their understanding and to make better alternatives. In this study, we evaluated the effects of reconstructing the discussion by focusing on the change of participants' wordings during the discussion. This study proposed two types of methodologies: “Overlapping rate” and “Classification of noun words”. The former identified the characteristics of the participants. The latter showed the change of participants' wordings after the reconstruction.

This study proposes three criteria to evaluate workshop discussions: social acceptability, adoption rate and context maintenance rate. Through WS discussion, various opinions and ideas are generated by the participants. Social acceptability shows the possibility that these opinions obtain the support of people in the community. Adoption rate shows how much participants' opinions are adopted for finally proposed plan. Context maintenance rate, on the other hand, shows how much their opinions are maintained in the next discussion. Two different types of workshop were compared using these criteria and also two different types of data were also compared. Social acceptability was positively correlated with adoption rate when the workshop aims at building consensus. Context maintenance rates of description data and dialogue data were compared, and low context maintenance rate in description data showed the possibility of rephrasing.

This study proposes the method of quantitative analysis on discussion in workshop for proper operation of discussion. It also shows the characteristics and the roles of discussion in workshop in planning process. There is a perception gap about policy issues of the region between planners who set up a workshop, and participants. The objectives of this study are to make clear its gap quantitatively, and to establish a management solution for minimizing them. This study provides quantitative analysis of a content of discussion to make participant's concern clear. The efficacy of this method is also discussed.

For succeeding in participatory decision making, participants need to understand concerns of other participants. In this paper, the model for describing a policy conflict is proposed. A policy conflict model requires participants, concerns and payoffs to be specified. Using the proposed policy conflict model, policy conflicts were classified into four types, bilateral conflict, unilateral conflict, isolation and incomplete participation. For each type of policy conflict, the means for governing a conflict was also discussed.

In regional planning, the importance of citizen participation has been emphasized. One of the purposes of participatory planning is to understand public opinion. Government can not necessarily know citizens' preferences on regional planning. By inviting representatives into the decision process, government can reflect citizens' needs to the alternative. In this study, an "interest party (stakeholder)" and an "authority of implementation" are regarded as distinguished players. It is assumed that government has an ability to design alternatives, but it can not know citizens' preferences completely. On the other hand, representative is supposed to represent citizens' interests. The model on representative's participation is constructed, and value of representative's participation is defined. It is also shown the value of participation depends on diversity of citizens' preference.

This paper intends to illustrate the potential value of game-theory in deriving policy implications for actual conflict situations, whereby the ongoing water resources development conflict, "the Yoshino River Weir Conflict" will be highlighted for illustration. The methodology of conflict analysis is used to systematically describe the process of changes in the structure of this conflict currently taking place in Tokushima, Shikoku, Japan. The potential power of modeling and interpreting actual conflicts by use of conflict analysis is systematically examined. The design of institutional and organizational schemes and instruments to resolve the conflict will also be discussed based on the methodology of game theory and conflict analysis.

When players with different interests try to achieve a better state, conflicts among players arise. Conflicts may arise also among public players. For example, a local government may insist on the interest of the region while the national government represents the interests of the whole country. Conflict analysis is one of the methods to model such conflicts mathematically. Its stability analysis specifies stable states based on the ordinal information on players' preferences. However, if the preference of a player is private, stability of states is not known. In such a case, players or third parties have to collect additional information on other players' preference. It is necessary to specify the minimum information to collect. In this paper, graph model for conflict resolution (GMCR) is extended for the cases with incomplete information. Then, the generalized robustness analysis is proposed to specify the minimum conditions for stability of states. Finally, robustness analysis is applied to the conflict on water resources development.

In this paper, the methodology to evaluate viability of a city is proposed. First, districts in a city are classified into two groups, based on the difference between the distributions of population and facilities. One is the group of districts with a relative abundance of facilities, and the other is the group of districts with a relative shortage of facilities. Then only the roads that connect the districts with a relative abundance of facilities and the districts with a relative shortage of facilities are regarded as effective links from the viewpoint of efficient use of facilities in a city. Topological index of the graph consisting of effective links is calculated to evaluate the ability of complementing functions. The application of the methodology to some cities is also shown.

In conflicts over large-scale infrastructure projects, public opinion may influence the preference structure of the players as they communicate with the general public who are considered to be outside of the game. We deal with the particular kind of conflict which allows for players' communication with the outside public which we shall call the public-open conflict. The major objective is to illustrate an example of a public-open conflict in an infrastructure project, by systematically examining a Japanese case study called the conflict over the Daiju-zeki (Daiju-weir) renewal project on the Yoshino River, Japan.

With a focus on a regional joint water distribution system, this paper proposes a cost allocation scheme which guarantees an equilibrium reached by participating regions (players) who are self-organized to form appropriate cooperative relations (coalitions). Two critical properties of regional joint water distribution systems are discussed, i.e., physical and social networks. Characteristics of cost functions are closely examined by referring to the manner in which social network structure bind the optimal (economically efficient) design of respective physical network structure. It is shown that economies of scale may not always hold for water distribution pipeline systems. The notions of equilibria based on Myerson's value coupled with 'component balance' and 'equal bargaining power' are proved to serve as the intended cost allocation scheme. With a joint regional distribution system as a case study, illustrations are made to demonstrate the applicability of the proposed cost allocation scheme.

The coordination scheme for reservoir renewal projects is suggested. It is assumed that asymmetry of information on benefits exists between agents (players) participating in the projects. A neutral organization called "planning coordinator" exercises this coordination scheme. First, it is mathematically proved that there exist incentives for participating players to make false statements to attain greater benefits unduly at the sacrifice of the counterpart under the conventional allocation scheme. Then, the coordination scheme in which discrete payment options with a finite number is suggested. In the coordination scheme, players report to the planning coordinator about prioritization of available alternatives of action relative to a status quo alternative. Such a payment option set is presented to the players in order to maximize the probability that renewal projects are realized.

Attention to CSCW has been increasing, resulting in greater needs for secure group communication. In order to realize secure group communication, data which is sent from a member to other members of a group should be encrypted by the cryptographic communication key of the group. We propose an identity-based non-interactive group communication key sharing scheme using smart cards based on the modified copy key (MCK) method. We assume that the smart cards contain the key generators and are secure for tampering. Each user has a smart card and a key generator. A user can generate a group communication key non-interactively with his key generator and the IDs of the other group members using his smart card.>