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Search Results: 1 - 10 of 5109 matches for " Giuseppe Perelli "
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On the Remarkable Features of Binding Forms
Fabio Mogavero,Giuseppe Perelli
Mathematics , 2014,
Abstract: Hilbert's Entscheidungsproblem has given rise to a broad and productive line of research in mathematical logic, where the classification process of decidable classes of first-order sentences represent only one of the remarkable results. According to the criteria used to identify the particular classes of interest, this process was declined into several research programs, of which some of the most deeply investigated are the ones classifying sentences in prenex normal form in base of their prefix vocabulary. Unfortunately, almost all of these approaches did not shed any light on the reasons why modal logic is so robustly decidable. Trying to answer to this question, Andreka, van Benthem, and Nemeti introduced the guarded fragment of first-order logic, which generalizes the modal framework by essentially retaining all its fundamental properties. They started, so, a completely new research program based on the way quantifications can be relativized. Although this approach succeeded in its original task, we cannot consider it satisfactory in spotting the reasons why some complex extensions of modal logic are well-behaved. In particular, by just using the related results, we are not able to derive the decidability of multi-agent logics for strategic abilities. In this paper, aiming to lay the foundation for a more thorough understanding of some of these decidability questions, we introduce a new kind of classification based on the binding forms that are admitted in a sentence, i.e., on the way the arguments of a relation can be bound to a variable. We describe a hierarchy of first-order fragments based on the Boolean combinations of these forms, showing that the less expressive one is already incomparable with the guarded logic and related extensions. We also prove, via a new model-theoretic technique, that it enjoys the finite-model property and a PSpace satisfiability problem.
A Decidable Fragment of Strategy Logic
Fabio Mogavero,Aniello Murano,Giuseppe Perelli,Moshe Y. Vardi
Mathematics , 2012,
Abstract: Strategy Logic (SL, for short) has been recently introduced by Mogavero, Murano, and Vardi as a useful formalism for reasoning explicitly about strategies, as first-order objects, in multi-agent concurrent games. This logic turns to be very powerful, subsuming all major previously studied modal logics for strategic reasoning, including ATL, ATL*, and the like. Unfortunately, due to its expressiveness, SL has a non-elementarily decidable model-checking problem and a highly undecidable satisfiability problem, specifically, $\Sigma_{1}^{1}$-Hard. In order to obtain a decidable sublogic, we introduce and study here One-Goal Strategy Logic (SL[1G], for short). This logic is a syntactic fragment of SL, strictly subsuming ATL*, which encompasses formulas in prenex normal form having a single temporal goal at a time, for every strategy quantification of agents. SL[1G] is known to have an elementarily decidable model-checking problem. Here we prove that, unlike SL, it has the bounded tree-model property and its satisfiability problem is decidable in 2ExpTime, thus not harder than the one for ATL*.
Reasoning About Strategies: On the Model-Checking Problem
Fabio Mogavero,Aniello Murano,Giuseppe Perelli,Moshe Y. Vardi
Mathematics , 2011,
Abstract: In open systems verification, to formally check for reliability, one needs an appropriate formalism to model the interaction between agents and express the correctness of the system no matter how the environment behaves. An important contribution in this context is given by modal logics for strategic ability, in the setting of multi-agent games, such as ATL, ATL\star, and the like. Recently, Chatterjee, Henzinger, and Piterman introduced Strategy Logic, which we denote here by CHP-SL, with the aim of getting a powerful framework for reasoning explicitly about strategies. CHP-SL is obtained by using first-order quantifications over strategies and has been investigated in the very specific setting of two-agents turned-based games, where a non-elementary model-checking algorithm has been provided. While CHP-SL is a very expressive logic, we claim that it does not fully capture the strategic aspects of multi-agent systems. In this paper, we introduce and study a more general strategy logic, denoted SL, for reasoning about strategies in multi-agent concurrent games. We prove that SL includes CHP-SL, while maintaining a decidable model-checking problem. In particular, the algorithm we propose is computationally not harder than the best one known for CHP-SL. Moreover, we prove that such a problem for SL is NonElementarySpace-hard. This negative result has spurred us to investigate here syntactic fragments of SL, strictly subsuming ATL\star, with the hope of obtaining an elementary model-checking problem. Among the others, we study the sublogics SL[NG], SL[BG], and SL[1G]. They encompass formulas in a special prenex normal form having, respectively, nested temporal goals, Boolean combinations of goals and, a single goal at a time. About these logics, we prove that the model-checking problem for SL[1G] is 2ExpTime-complete, thus not harder than the one for ATL\star.
Reformas a los sistemas electorales: Algunas reflexiones desde la práctica
Perelli,Carina;
Revista de ciencia política (Santiago) , 2006, DOI: 10.4067/S0718-090X2006000100013
Abstract: what we know as electoral engineering is a set of technical tools aimed at the design or reform of electoral systems to better adjust them to the evolving reality of a country. beyond design, however, there is a vast field composed of the actual practice of implementation of these reforms and the lessons learned from it through time. these pages, written from a practitioner's and not a scholar's point of view, highlight some of the lessons the electoral community learned through concrete experiences of design and reform of electoral systems in conflict areas, and proposes some best practices to contribute to the current debate on electoral reform in chile
Reformas a los sistemas electorales: Algunas reflexiones desde la práctica
Carina Perelli
Revista de Ciencia Política , 2006,
Abstract: La ingeniería electoral es una herramienta técnica que permite dise ar cambios en los sistemas electorales para acompasarlos a la cambiante realidad política de un país. Más allá del dise o, sin embargo, existe la implementación de las reformas y las lecciones que operan dichos sistemas en la práctica y que han dictado a lo largo de los a os. Estas reflexiones, que no pretenden ser académicas, rescatan algunos de los aprendizajes realizados por la comunidad electoral en su práctica concreta como un aporte para una reflexión más amplia al debate actual de la reforma electoral en Chile What we know as electoral engineering is a set of technical tools aimed at the design or reform of electoral systems to better adjust them to the evolving reality of a country. Beyond design, however, there is a vast field composed of the actual practice of implementation of these reforms and the lessons learned from it through time. These pages, written from a practitioner's and not a scholar's point of view, highlight some of the lessons the electoral community learned through concrete experiences of design and reform of electoral systems in conflict areas, and proposes some best practices to contribute to the current debate on electoral reform in Chile
pHp|Tek 2007, pHp::innovation( )
Matteo Perelli
Bollettino del CILEA , 2007, DOI: 10.1472/bc.v107i0.1357
Abstract: A Chicago (Illinois U.S.A.), dal 15 al 18 maggio, si è svolto l’annuale incontro organizzato dalla rivista ‘pHp Architect’, la conferenza internazionale ‘pHp|Tek’ [1]. Quest’anno gli interventi degli oratori si sono concentrati sui temi della sicurezza, delle performance e su come sia possibile ottimizzare i tempi di sviluppo; tre aspetti che hanno contribuito alla costante crescita di pHp a livello internazionale e che hanno convinto molte società di qualunque dimensione a includere al loro interno un team di sviluppo in questo linguaggio. This year ‘pHp|Tek’ [2] conference (organized by the editors of ‘pHp Architect’ journal) took place in Chicago (Illinois U.S.A.) from May 15th to 18th. Security, performance and methods to ‘build better application faster’ were the main topics; these are the three major aspects of pHp that made it so popular. In fact several companies have decided to include a pHp developing team in their staff.
Ukraine: On the border between old and new in uncertain times
Brienna Perelli-Harris
Demographic Research , 2008,
Abstract: This chapter provides an overview of the demographic situation in Ukraine, including explanations for the decline to very low fertility and changes in family policy. Drawing on official statistics, survey data, and focus group interviews, the analysis shows that the country's decline to lowest-low fertility is primarily due to the postponement of or the reduction in second births, as opposed to the postponement of first births. The chapter includes a discussion on the link between low fertility and changing marriage patterns, contraceptive prevalence, and abortion. The author then reviews the evidence for the leading explanations of fertility decline in Ukraine, including economic uncertainty, social anomie, the Second Demographic Transition, and unequal gender relations. In addition, the author proposes unexplored factors that may lead to fertility limitation, such as the increasing difficulty of combining work and childrearing, insufficient housing, changes in intergenerational support, and the deterioration of health lifestyles and marital relations.
Codex[ml]
Matteo Perelli,Carla Zini
Bollettino del CILEA , 2007, DOI: 10.1472/bc.v107i0.1351
Abstract: Codex[ml] integrated system has been developed by CILEA with the aim of meeting management, storage and fruition requirements of digital objects. Using Codex[ml] every agency and every library that deals with organ ized information can offer the fruition of its own works, text or archives, through an on-line navigation based on different xml metadata standards. Codex[ml] performs import, creation, long-term storage, delivery and fruition of xml documents that follow administrative standards for data management. It is an open system, which is able to manage METS, MAG and other standards, even not yet developed (adding new metadata interface modules). This is a modular and scalar software: every component is developed over a common framework to guarantee full interoperability. Il sistema integrato Codex[ml] è stato sviluppato dal CILEA per la gestione, conservazione e fruizione via web di risorse digitali. La piattaforma consente a ogni istituzione culturale, biblioteca o archivio che possieda informa zioni cartacee digitalizzate, la relativa fruizione attraverso la navigazione via web, sfruttando l’analisi dei diversi standard di metadati, in linguaggio XML. Il sistema si presenta modulare e scalabile: ogni modulo è un elemento indipendente che interagisce con gli altri per garantire la possibilità di creare, conservare, distribuire immagini corredate da metadati. L’utente può navigare all’interno della risorsa digitale visualizzandola con un’interfaccia web, sfruttando la struttura descritta nei metadati, codificati in linguaggio XML, secondo le specifiche previste dagli standard METS, MAG, etc., ma predisposta anche per nuovi standard non ancora scritti.
Twists, Euler products and a converse theorem for $L$-functions of degree 2 in the Selberg class
J. Kaczorowski,A. Perelli
Mathematics , 2012, DOI: 10.2422/2036-2145.201301_003
Abstract: We prove a general result relating the shape of the Euler product of an $L$-function to the analytic properties of certain linear twists of the $L$-function itself. Then, by a sharp form of the transformation formula for linear twists, we check the required analytic properties in the case of $L$-functions of degree 2 and conductor 1 in the Selberg class. Finally we prove a converse theorem, showing that $\zeta(s)^2$ is the only member of the Selberg class satisfying the above conditions and, moreover, having a pole at $s=1$.
Twists and resonance of L-functions, I
J. Kaczorowski,A. Perelli
Mathematics , 2013,
Abstract: We obtain the basic analytic properties, i.e. meromorphic continuation, polar structure and bounds for the order of growth, of all the nonlinear twists with exponents $\leq 1/d$ of the L-functions of any degree $d \geq 1$ in the extended Selberg class. In particular, this solves the resonance problem in all such cases.
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