On consistent coalitions in group decision making with flexible decision makers

In this paper we propose a formal framework to deal with situations of group decision making with flexible decision makers. In the framework it is assumed that each decision maker tries to achieve cooperation in a coalition balancing their flexibility as well as to obtain a consequence as desirable for him/herself as possible. We introduce two different concepts of consistency of coalitions in order to express the idea of the assumption, and examine relations between them. We, moreover, define two types of strategic exchanges of information about decision makers' opinions, and provide a sufficient condition to make profitable manipulation of information impossible, in each case. That is, it is impossible for a decision maker to obtain a preferable consequence by strategic information exchange, when the decision maker cannot form any new consistent coalitions by the manipulated information, in both cases. (C) 2000 Elsevier Science Inc. All rights reserved.