Discussion note on logic for group decisions

A group decision support system uses a knowledge base created by the active participation of the group members. Uncertainties can be introduced in such a group knowledge base from at least two sources: hard uncertainties can result from a lack of knowledge on the part of every group member about some state of affairs in the world, and soft uncertainties can result from a lack of consensus among the group members. A logical infrastructure is necessary to support query processing and drawing inferences from a group knowledge base. It is shown that a natural formulation of logic in this case leads to a many-valued logic that has significant differences from traditional logic. Some basic operations in this logic are derived.<>