Browsing by Author "Dias, Luís"
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- Approaches to suggest potential agreements: Perspectives of mediation with incomplete informationPublication . Sarabando, Paula; Dias, Luís; Vetschera, RudolfIn bilateral Negotiation Analysis, the literature often co nsiders the case of complete information. In this context, since the negotiators know the value functions of both parties, it is not difficult to calculate the Pareto frontier and the Pareto efficient soluti ons for the negotiation. Thus rational negotiators can reach agreement on this frontier. However, these approaches are not applied in practice when the parties do not have complete information. The research question of our work is “It is possible to help negotiators achieving an efficient soluti on if they do not have complete information regarding the different parameters of the model?”. We propos e to obtain information regarding the preferences of negotiators during the negotiation process , in order to be able to propose alternatives close to the Pareto frontier. During this work we will presen t three approaches to help a mediator proposing a better solution than the compromise the negotia tors have reached or are close to reach.
- Comparison of decision rules to mediate negotiations with incomplete informationPublication . Sarabando, Paula; Dias, LuísDecisions in society resulting from negotiation among two parties are often inefficient (in terms of Pareto efficiency) as the parties fail to identify an agreement that would make both better off. A third party mediating the negotiation can increase the chances of reaching a Pareto efficient alternative. However, in most practical situations the mediator does not have a precise model of the parties’ preferences, and therefore cannot identify which alternatives are efficient. This paper assesses the performance of decision rules that a mediator can apply in multi-issue bilateral negotiation analysis given ordinal information about the importance of the issues and the value of the potential alternatives in each issue. We assume the preferences of the parties can be modelled by an additive multiattribute value function, but without assuming the precise parameters of this model are known. We study three mediation criteria: maximising the sum of the values, maximising the product of the excesses, or maximising the minimal proportion of potential. Monte-Carlo simulation is used to assess how good the alternative chosen by each decision rule is, and to provide guidelines about the use of these rules in a context of selecting a subset of promising alternatives.
- Information levels in additive group decision models under incomplete information: Bridging the cardinal ordinal gapPublication . Vetschera, Rudolf; Dias, Luís; Sarabando, PaulaIn the literature, several models for group decision making based on the additive aggregation of group members’ utility or value functions have been proposed (Keeney and Kirkwood 1975; Dyer and Sarin 1979; Keeney and Nau 2011). These group aggregation rules usually are based on systems of axioms very similar to those formulated by Arrow (1963) for the case of aggregating ordinal preferences. In contrast to aggregation of ordinal preferences, aggregation of cardinal alues is thus possible in groups. However, it requires group members to specify their preferences in cardinal form, by assigning utility scores to alternatives. This could be difficult for group members, in particular if this information should be provided exactly.
- Mediation with Incomplete Information: Approaches to Suggest Potential AgreementsPublication . Sarabando, Paula; Dias, Luís; Vetschera, RudolfIn bilateral Negotiation Analysis, the literature often considers the case of complete information. In this context, since the negotiators know the value functions of both parties, it is not difficult to calculate the Pareto efficient solutions for the negotiation. Thus rational negotiators can reach agreement on this frontier. However, these approaches are not applied in practicewhen complete information is not available. The research question of ourwork is “It is possible to help negotiators achieving an efficient solution in the absence of complete information regarding the different parameters of the model?”. We propose to derive incomplete information about the preferences of negotiators from the statements they make and the offers they exchange during the negotiation process. We present and discuss three approaches that use this information in order to help a mediator proposing a better solution than the compromise the negotiators have reached or are close to reach.
- Multi-attribute choice with ordinal information: a comparison of different decision rulesPublication . Sarabando, Paula; Dias, LuísIn the context of additive multiattribute aggregation, we address problems with ordinal information, i.e., considering a ranking of the weights (the scaling coefficients). Several rules for ranking alternatives in these situations have been proposed and compared, such as the rank-order-centroid weight, minimum value, central value, and maximum regret rules. This paper compares these rules, together with two rules that had never been studied (quasi-dominance and quasi-optimality) that use a tolerance parameter to extend the concepts of dominance and optimality. Another contribution of this paper is the study of the behavior of these rules in the context of selecting a subset of the most promising alternatives. This study intends to provide guidelines about which rules to choose and how to use them (e.g., how many alternatives to retain and what tolerance to use), considering the contradictory goals of keeping a low number of alternatives yet not excluding the best one. The comparisons are grounded on Monte Carlo simulations.
- A Note on a Group Preference Axiomatization with Cardinal UtilityPublication . Dias, Luís; Sarabando, PaulaKenneth Arrow’s work on social welfare proposed a set of conditions that a function to aggregate ordinal preferences of the members of a group should satisfy, proving that it was not possible to satisfy all these assumptions simultaneously. Later, Ralph Keeney adapted these conditions and proposed a cardinal utility axiomatization for the problem of aggregating the utility functions. This note discusses in particular the condition of nondictatorship. It proposes stronger formulations for this condition to limit the maximum influence that an individual can have, and it presents the corresponding characterization of compliant group cardinal utility functions. An extension to address coalitions of individuals acting strategically is also discussed.
- On a Group Preference Axiomatization with Cardinal UtilityPublication . Dias, Luís; Sarabando, PaulaArrow proposed a set of conditions for a function to aggregate ordinal preferences of the members of a group, proving that it was not possibl e to satisfy all these assumptions simultaneously. Later, Keeney adapted these conditions and proposed a cardinal utility axiomatization for the problem of aggregating the utility functions. This work dis cusses the condition of nondictatorship. It propose s a stronger formulation for this condition and prese nts the corresponding characterization of group cardinal utility functions.
- Simple procedures of choice in multicriteria problems without precise information about the alternatives’ valuesPublication . Sarabando, Paula; Dias, LuísThe additive model of multiattribute value (or utility) the ory is widely used in multicriteria choice problems. However, often it is not easy to obtain precise values for the scaling weights or the alterna tives’ value in each function. Several decision rules have been proposed to select an alternative under these circumstances, which require weak er information, such as ordinal information. We propose new decision rules a nd test them using Monte-Carlo simulation, considering that there exists ordinal information both on the scaling weights and on the alternati ves’ values. Results show the new rules constitute a good approximation. We provide guidelines about how to use these rules in a context of select ing a subset of the most promising alternatives, considering the contradi ctory objectives of keeping a low number of alternatives yet not excluding the best one.
- Simple procedures of choice in multicriteria problems without precise information about the alternatives’ valuesPublication . Sarabando, Paula; Dias, Luís