Many systems that exhibit nonmonotonic behavior have been described and studied already in the literature. The general notion of nonmonotonic reasoning, though, has almost always been described only… (More)

Some important classical mechanisms considered in Microeconomics and Game Theory require the solution of a difficult optimization problem. This is true of mechanisms for combinatorial auctions, which… (More)

In most of microeconomic theory, consumers are assumed to exhibit decreasing marginal utilities. This paper considers combinatorial auctions among such buyers. The valuations of such buyers are… (More)

The lexicographic closure of any given finite setD of normal defaults is defined. A conditional assertiona ❘∼b is in this lexicographic closure if, given the defaultsD and the facta, one would… (More)

It is shown that distributed systems of probabilistic processors are essentially more powerful than distributed systems of deterministic processors, i.e., there are certain useful behaviors that can… (More)

Finding optimal solutions for multi-unit combinatorial auctions is a hard problem and nding approximations to the optimal solution is also hard. We investigate the use of Branch-and-Bound techniques:… (More)

The temporal propositional logic of linear time is generalized to an uncertain world, in which random events may occur. The formulas do not mention probabilities explicitly, i.e., the only… (More)