Asymptotically idempotent aggregation operators for trust management in multi-agent systems

The study of trust management in multi-agent system, especially distributed, has grown over the last years. Trust is a complex subject that has no general consensus in literature, but has emerged the importance of reasoning about it computationally. Reputation systems takes into consideration the history of an entity’s actions/behavior in order to compute trust, collecting and aggregating ratings from members in a community. In this scenario the aggregation problem becomes fundamental, in particular depending on the environment. In this paper we describe a technique based on a class of asymptotically idempotent aggregation operators, suitable particulary for distributed anonymous environments

A note on a Tarski type fixed-point theorem

AbstractIn this paper we propose a basic fixed-point theorem for correspondences inspired by Tarski's intersection point theorem. This result furnishes an efficient tool to prove the existence of pure strategy Nash equilibria for two player games with possibly discontinuous payoffs functions defined on compact real intervals

Axiomatization of residual income and generation of financial securities

This paper presents an axiomatization of residual income, aka excess profit, and illustrates how it may univocally engenders fixed-income or variable-income assets. In the first part it is shown that, depending on the relations between excess profit and the investor's excess wealth, a well-specified theory of residual income is generated: one is the standard theory, which historically traces back to Hamilton (1777) and Marshall (1890) and is a deep-rooted notion in economic theory, finance, and accounting. Another one is the systemic value added or lost-capital paradigm: introduced in Magni (2000, 2003), the theory is enfolded in Keynes's (1936) notion of user cost and is naturally generated by an arbitrage-theory perspective. In the second part, the paper reverts the usual analysis: instead of computing residual incomes profits from a pattern of cash flows, residual incomes are fixed first to derive vectors of cash flows. It is shown that variable- or fixed-income assets may be constructed on the basis of either theory starting from pre-determined growth rates for excess profit. In particular, zero-coupon bonds and coupon bonds traded in a capital market are shown to be deducted as equilibrium vectors of residual-income-based assets.Residual income, excess profit, capital, arbitrage, bond

Axiomatization of residual income and generation of financial securities

This paper presents an axiomatization of residual income, aka excess profit, and illustrates how it may univocally engenders fixed-income or variable-income assets. In the first part it is shown that, depending on the relations between excess profit and the investor's excess wealth, a well-specified theory of residual income is generated: one is the standard theory, which historically traces back to Hamilton (1777) and Marshall (1890) and is a deep-rooted notion in economic theory, finance, and accounting. Another one is the systemic value added or lost-capital paradigm: introduced in Magni (2000, 2003), the theory is enfolded in Keynes's (1936) notion of user cost and is naturally generated by an arbitrage-theory perspective. In the second part, the paper reverts the usual analysis: instead of computing residual incomes profits from a pattern of cash flows, residual incomes are fixed first to derive vectors of cash flows. It is shown that variable- or fixed-income assets may be constructed on the basis of either theory starting from pre-determined growth rates for excess profit. In particular, zero-coupon bonds and coupon bonds traded in a capital market are shown to be deducted as equilibrium vectors of residual-income-based assets

Supermigrativity of aggregation functions

A functional inequality, called supermigrativity, was recently introduced for bivariate semi-copulas and applied in various problems arising in the study of aging properties of stochastic systems. Here, we revisit this notion and extend it to the case of aggregation functions in higher dimensions. In particular, we show how supermigrativity can be expressed via monotonicity of a function with respect to logarithmic majorization ordering of real vectors. Various alternative characterizations of supermigrativity are illustrated, together with some of its weaker versions. Several examples show similarities and differences between the bivariate and the general case

Multi-attribute aggregation operators

This paper deals with the idea of aggregation. A new, enlarged notion of aggregation operator is given, along with a classification of classical properties into some main groups. The concept of multi-attribute aggregation operator, which incorporates many classical aggregation methods, is provided. An extension of different properties to multi-attribute aggregation operators is proposed. © 2011 Elsevier B.V. All rights reserved

An axiomatic approach to a class of ranking functions for triangular fuzzy numbers

none1This paper deals with the problem of ranking a set of alternatives, represented by triangular fuzzy numbers. A new approach is followed through the definition of some axiomatic requirements which represent the essential properties that characterize an arbitrary ranking function. A notion of degree of risk associated to every ranking function is proposed to discriminate equivalent alternatives.noneR. GHISELLI RICCIGHISELLI RICCI, Robert

On the characterization of topological semigroups on closed intervals

none1Topological linearly ordered semigroups defined on connected and compact sets are studied. Particularly, two representation theorems for the o-embedding of such semigroups into the real numbers with standard operations are provided, weakening the crucial assumption of cancellativity. A generalized notion of o-isomorphism, which includes the classical case even if cancellativity falls, is given.noneR. GHISELLI RICCIGHISELLI RICCI, Robert

Characterization of non-nilpotent topological interval semigroups

none1A remarkable subclass of linearly ordered semigroups, called interval semigroups, defined on connected and compact sets is studied. Particularly, a generalized notion of o-isomorphism, called weak o-embedding, of such semigroups into the real numbers with standard operations is given. A representation theorem for the weak o-embedding of topological Archimedean interval semigroups with no zero divisors is provided. Such characterization is shown to be the best one possible.openR. GHISELLI RICCIGHISELLI RICCI, Robert