Optimism and pessimism in strategic interactions under ignorance

We study players interacting under the veil of ignorance, who have—coarse—beliefs represented as subsets of opponents' actions. We analyze when these players follow max⁡min or max⁡max decision criteria, which we identify with pessimistic or optimistic attitudes, respectively. Explicitly formalizing these attitudes and how players reason interactively under ignorance, we characterize the behavioral implications related to common belief in these events: while optimism is related to Point Rationalizability, a new algorithm—Wald Rationalizability—captures pessimism. Our characterizations allow us to uncover novel results: (i) regarding optimism, we relate it to wishful thinking á la Yildiz (2007) and we prove that dropping the (implicit) “belief-implies-truth” assumption reverses an existence failure described therein; (ii) we shed light on the notion of rationality in ordinal games; (iii) we clarify the conceptual underpinnings behind a discontinuity in Rationalizability hinted in the analysis of Weinstein (2016)

Some Lambda Calculus and Type Theory Formalized

"This paper is about our hobby." That is the first sentence of [MP93], the first report on our formal development of lambda calculus and type theory, written in autumn 1992. We have continued to pursue this hobby on and off ever since, and have developed a substantial body of formal knowledge, including Church-Rosser and standardizationtheorems for beta reduction, and the basic theory ofPure Type Systems (PTS) leading to the strengthening theorem and type checking algorithms for PTS. Some of this work is reported in [MP93, vBJMP94, Pol94b, Pol95]. In the present paper we survey this work, including some new proofs, and point out what we feel has been learned about the general issues of formalizing mathematics. On the technical side, we describe an abstract, and simplified, proof of standardization for beta reduction, not previously published, that doesnot mention redex positions or residuals. On the general issues, we emphasize the search for formal definitions that are convenient for formal proof and convincingly represent the intended informal concepts. The LEGO Proof Development System [LP92] was used to check the work in an implementation of the Extended Calculus of Constructions(ECC) with inductive types [Luo94]. LEGO is a refinement styleproof checker, publicly available by ftp and WWW, with a User's Manual [LP92] and a large collection of examples. Section 1.3 contains information on accessing the formal development described in this paper. Other interesting examples formalized in LEGO include program specification and data refinement [Luo91], strong normalization of System F [Alt93], synthetic domain theory [Reu95, Reu96], and operational semantics for imperative programs [Sch97]

Computing repairs for constraint violations in UML/OCL conceptual schemas

Updating the contents of an information base may violate some of the constraints defined over the schema. The classical way to deal with this problem has been to reject the requested update when its application would lead to some constraint violation. We follow here an alternative approach aimed at automatically computing the repairs of an update, i.e., the minimum additional changes that, when applied together with the requested update, bring the information base to a new state where all constraints are satisfied. Our approach is independent of the language used to define the schema and the constraints, since it is based on a logic formalization of both, although we apply it to UML and OCL because they are widely used in the conceptual modeling community. Our method can be used for maintaining the consistency of an information base after the application of some update, and also for dealing with the problem of fixing up non-executable operations. The fragment of OCL that we use to define the constraints has the same expressiveness as relational algebra and we also identify a subset of it which provides some nice properties in the repair-computation process. Experiments are conducted to analyze the efficiency of our approach.Peer ReviewedPostprint (author's final draft

Computational accountability in MAS organizations with ADOPT

This work studies how the notion of accountability can play a key role in the design and realization of distributed systems that are open and that involve autonomous agents that should harmonize their own goals with the organizational goals. The socio–technical systems that support the work inside human companies and organizations are examples of such systems. The approach that is proposed in order to pursue this purpose is set in the context of multiagent systems organizations, and relies on an explicit specification of relationships among the involved agents for capturing who is accountable to whom and for what. Such accountability relationships are created along with the agents’ operations and interactions in a shared environment. In order to guarantee accountability as a design property of the system, a specific interaction protocol is suggested. Properties of this protocol are verified, and a case study is provided consisting of an actual implementation. Finally, we discuss the impact on real-world application domains and trace possible evolutions of the proposal

Teoria tradicional da informação semântica sem escândalo da dedução : uma reavaliação moderadamente externalista do tópico baseada em semântica urna e uma aplicação paraconsistente

Orientador: Walter Alexandre CarnielliTese (doutorado) - Universidade Estadual de Campinas, Instituto de Filosofia e Ciências HumanasResumo: A presente tese mostra que é possível reestabelecer a teoria tradicional da informação semântica (no que segue apenas TSI, originalmente proposta por Bar-Hillel e Carnap (1952, 1953)) a partir de uma descrição adequada das condições epistemológicas de nossa competência semântica. Uma consequência clássica de TSI é o assim chamado escândalo da dedução (no que segue SoD), tese segundo a qual verdades lógicas têm quantidade nula de informação. SoD é problemático dado que conflita com o caráter ampliativo do conhecimento formal. Baseado nisso, trabalhos recentes (e.g., Floridi (2004)) rejeitam TSI apesar de suas boas intuições sobre a natureza da informação semântica. Por outro lado, esta tese reconsidera a estratégia de assumir a semântica urna (RANTALA, 1979) como o pano de fundo metateórico privilegiado para o reestabelecimento de TSI sem SoD. A presente tese tem o seguinte plano. O capítulo 1 introduz o plano geral da tese. No capítulo 2, valendo-se fortemente de trabalhos clássicos sobre o externalismo semântico, eu apresento algum suporte filosófico para essa estratégia ao mostrar que a semântica urna corretamente caracteriza as condições epistemológicas de nossa competência semântica no uso de quantificadores. O capitulo 3 oferece uma descrição precisa da semântica urna a partir da apresentação de suas definições básicas e alguns de seus teoremas mais funda- mentais. No capítulo 4, eu me concentro mais uma vez no tema da informação semântica ao formalizar TSI em semântica urna e provar que nesse contexto SoD não vale. Finalmente, nos capítulos 5 e 6 eu considero resultados modelo-teóricos mais avançados sobre semântica urna e exploro uma possível aplicação paraconsistente das ideias principais dessa tese, respectivamenteAbstract: This thesis shows that it is possible to reestablish the traditional theory of semantic information (TSI, originally proposed by Bar-Hillel and Carnap (1952, 1953)) by providing an adequate account of the epistemological conditions of our semantic competence. A classical consequence of TSI is the so-called scandal of deduction (hereafter SoD) according to which logical truths have null amount of information. SoD is problematic since it does not make room for the ampliative character of formal knowledge. Based on this, recent work on the subject (e.g., Floridi (2004)) rejects TSI despite its good insights on the nature of semantic information. On the other hand, this work reconsiders the strategy of taking urn semantics (RANTALA, 1979) as a privileged metatheoretic framework for the formalization of TSI without SoD. The present thesis is planned in the following way. Chapter 1 introduces the thesis¿ overall plan. In chapter 2, relying heavily on classical works on semantic externalism, I present some philosophical support for this strategy by showing that urn semantics correctly characterizes the epistemological conditions of our semantic competence in the use of quantifiers. Chapter 3 offers a precise description of urn semantics by characterizing its basic definitions and some of its most fundamental theorems. In chapter 4, turning the focus once again to semantic information, I formalize TSI in urn semantics and show that in this context SoD does not hold. Finally, in chapter 5 and 6 I consider more advanced model-theoretic results on urn semantics and explore a paraconsistent possible application of the present idea, respectivelyDoutoradoFilosofiaDoutor em Filosofia142038/2014-8CNP