FROTA, Débora Farias. Uma lógica de descrição Default. 2011. 79 f. Dissertação (Mestrado em ciência da computação)- Universidade Federal do Ceará, Fortaleza-CE, 2011. / Submitted by Elineudson Ribeiro (elineudsonr@gmail.com) on 2016-07-11T13:21:13Z No. of bitstreams: 1 2011_dis_dffrota.pdf: 945021 bytes, checksum: 9adb958d87b14104dcd8db9fc4c4bd6f (MD5) / Approved for entry into archive by Rocilda Sales (rocilda@ufc.br) on 2016-07-15T13:25:42Z (GMT) No. of bitstreams: 1 2011_dis_dffrota.pdf: 945021 bytes, checksum: 9adb958d87b14104dcd8db9fc4c4bd6f (MD5) / Made available in DSpace on 2016-07-15T13:25:42Z (GMT). No. of bitstreams: 1 2011_dis_dffrota.pdf: 945021 bytes, checksum: 9adb958d87b14104dcd8db9fc4c4bd6f (MD5) Previous issue date: 2011 / Knowledge formalization and reasoning automatization are central within Arti cial Intelligence. First Order Logic has been traditionally used for such purposes. However, it is better suited to deal with complete knowledge in ideal circumstances. In real situations, in which the knowledge is partial, First Order Logic is not su cient. Nonmonotonic logics have been proposed to better cope with practical reasoning. A successful formalization of nonmonotonic reasoning is the Reiter's default logic which extends classical logic with default rules. Unfortunately, default logic is undecidable. In this work, we propose a description default logic expressible enough to formalize practical reasoning in knowledge bases. It has as its monotonic basis the ALC Description Logic. We add some restrictions to the application of defaults in order to obtain nice properties such as coherence and the elimination of anomalous extensions. We present the main algorithms used to build an extension with a step by step complexity analysis. / A formalização do conhecimento e a automatização do raciocínio são assuntos centrais de pesquisa da Inteligência Artificial. A Lógica de Primeira Ordem tem sido tradicionalmente utilizada para tais propósitos. No entanto, ela é mais adequada para lidar com conhecimento completo em circunstâncias ideais. Em situações reais, nas quais o conhecimento é parcial, a Lógica de Primeira Ordem não é suficiente. Lógicas não-monotônicas têm sido propostas para melhor lidar com o raciocínio prático. Uma formalização do raciocínio não-monotônico bem-sucedida é a Lógica Default de Reiter que estende a Lógica de Primeira Ordem com regras default. Infelizmente, a Lógica Default é indecidível. Nesta dissertação, propomos uma Lógica de Descrição Default expressiva o suficiente para formalizar o raciocínio prático sobre bases de conhecimento. Ela tem como base monotônica a Lógica de Descrição ALC. Adicionamos algumas restrições à aplicação dos defaults a fim de obter propriedades interessantes, tais como a coerência e a eliminação de extensões anômalas. Apresentamos os principais algoritmos usados para construir uma extensão com um passo-a-passo e suas análise de complexidade.

VERAS, Rodrigo de Melo Souza. Uma nova abordagem para o raciocinio não monotônico. 2007. 102 f. Dissertação (Mestrado em ciência da computação)- Universidade Federal do Ceará, Fortaleza-CE, 2007. / Submitted by Elineudson Ribeiro (elineudsonr@gmail.com) on 2016-07-12T16:47:33Z No. of bitstreams: 1 2007_dis_rmsveras.pdf: 1095797 bytes, checksum: 0e461d552478b8849c4691529b7a5a91 (MD5) / Approved for entry into archive by Rocilda Sales (rocilda@ufc.br) on 2016-07-21T16:12:24Z (GMT) No. of bitstreams: 1 2007_dis_rmsveras.pdf: 1095797 bytes, checksum: 0e461d552478b8849c4691529b7a5a91 (MD5) / Made available in DSpace on 2016-07-21T16:12:24Z (GMT). No. of bitstreams: 1 2007_dis_rmsveras.pdf: 1095797 bytes, checksum: 0e461d552478b8849c4691529b7a5a91 (MD5) Previous issue date: 2007 / Default logic was introduced to manipulate reasoning with incomplete information and became the main paradigm to formalize nonmonotonic reasoning. Many variations have been proposed with the objective to solve some limitations of the formalism or to consider different intuitions on the role of inconclusive information. However, some of the main characteristics had been kept: inconclusive information is represented as default rules, objectifies the calculation of extensions and, because this, they use characterizations through fixed-point operators. We consider a new approach for nonmonotonic reasoning. In this dissertation, we present the Defeasible Logic with Exception-First. The main advantages of this approach are: it does not use fixed-points operators to define expansions (our correspondent of extensions) and exception-first property that does not allow that a inconclusive proposition intervenes with the derivation of its exception. Moreover, we present a new way to define the extensions of default logic and two of its main variants, justified default logic and constrained default logic. / A lógica default foi introduzida para manipular raciocínio com conhecimento incompleto e tornou-se o principal paradigma para a formalização do raciocínio não monotônico. Muitas variações foram propostas com o objetivo de solucionar algumas limitações do formalismo ou para proporem diferentes intuições sobre o papel das informações inconlusivas. Porém, algumas das principais características foram mantidas: a informação inconclusiva é representada por regras default, objetivam o cálculo de extensões e, para isso, utilizam uma caracterização através de operadores de ponto fixo. Nós propomos uma nova abordagem para o raciocínio não monotônico. Nesta dissertação, apresentamos a Lógica Defeasible com Prioridade às Exceções. As principais vantagens desta proposta são a não utilização de pontos fixos para definição das expansões (nosso correspondente de extensões) e a propriedade de prioridade às exceções que não permite que uma proposição inconclusiva interfira na derivação de sua exceção. Além disso, apresentamos uma nova maneira de definir as extensões da lógica default e de duas das suas principais variantes a lógica default justificada e a lógica default com restrições.

This thesis explores the effects of institutions on macroeconomic performance. It does so in two main chapters, a summary of each of which is given below. In the first main chapter of the thesis, the interactions between government spending, government borrowing, political corruption and political turnover were examined. Incorporating these factors in a sovereign default model, we show how sovereign default decisions and business cycle fluctuations are affected by the level of corruption. In particular, we show that when there is turnover, corruption can generate higher risks of default and higher credit spreads when there is enough stability. Intuitively, we establish that a change in power from a less corrupt to a more corrupt government is more likely to cause default than the reverse. The results also shows that households suffer welfare losses as a result of corruption. As regards business cycles, the general effect of corruption is to alter business cycle statistics. Further, we estimate an empirical model using data on sovereign default, corruption, political stability and other macroeconomic variables for a sample of emerging economies. The results of this provide strong evidence of a positive relationship between both corruption and political stability and sovereign default. The second main chapter of the thesis looks at the effects of limited financial contract enforcement in a dynamic stochastic general equilibrium framework where firms have access to both internal and external means of finance. The results shows how limited enforceability affects fluctuations in key macroeconomic variables (e.g., output, employment and price) through its impact on key financial variables (e.g., interest rates, risk premium, default risk and leverage). In particular, we find that weaker enforcement tends to amplify the effects of shocks, creating greater volatility, as well as lowering small firm funding. We provide some empirical evidence to support our results. Using cross-country data on measures of financial market imperfections, we find that limited enforcement has a negative effect on output and that this effect is exacerbated by poor credit information. We also find that weaker contract enforcement is associated with higher output volatility.

nÃo hà / A lÃgica default foi introduzida para manipular raciocÃnio com conhecimento incompleto e tornou-se o principal paradigma para a formalizaÃÃo do raciocÃnio nÃo monotÃnico. Muitas variaÃÃes foram propostas com o objetivo de solucionar algumas limitaÃÃes do formalismo ou para proporem diferentes intuiÃÃes sobre o papel das informaÃÃes inconlusivas. PorÃm, algumas das principais caracterÃsticas foram mantidas: a informaÃÃo inconclusiva à representada por regras default, objetivam o cÃlculo de extensÃes e, para isso, utilizam uma caracterizaÃÃo atravÃs de operadores de ponto fixo. NÃs propomos uma nova abordagem para o raciocÃnio nÃo monotÃnico. Nesta dissertaÃÃo, apresentamos a LÃgica Defeasible com Prioridade Ãs ExceÃÃes. As principais vantagens desta proposta sÃo a nÃo utilizaÃÃo de pontos fixos para definiÃÃo das expansÃes (nosso correspondente de extensÃes) e a propriedade de prioridade Ãs exceÃÃes que nÃo permite que uma proposiÃÃo inconclusiva interfira na derivaÃÃo de sua exceÃÃo. AlÃm disso, apresentamos uma nova maneira de definir as extensÃes da lÃgica default e de duas das suas principais variantes a lÃgica default justificada e a lÃgica default com restriÃÃes. / Default logic was introduced to manipulate reasoning with incomplete information and became the main paradigm to formalize nonmonotonic reasoning. Many variations have been proposed with the objective to solve some limitations of the formalism or to consider different intuitions on the role of inconclusive information. However, some of the main characteristics had been kept: inconclusive information is represented as default rules, objectifies the calculation of extensions and, because this, they use characterizations through fixed-point operators. We consider a new approach for nonmonotonic reasoning. In this dissertation, we present the Defeasible Logic with Exception-First. The main advantages of this approach are: it does not use fixed-points operators to define expansions (our correspondent of extensions) and exception-first property that does not allow that a inconclusive proposition intervenes with the derivation of its exception. Moreover, we present a new way to define the extensions of default logic and two of its main variants, justified default logic and constrained default logic.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / A formalizaÃÃo do conhecimento e a automatizaÃÃo do raciocÃnio sÃo assuntos centrais de pesquisa da InteligÃncia Articial. A LÃgica de Primeira Ordem tem sido tradicionalmente utilizada para tais propÃsitos. No entanto, ela à mais adequada para lidar com conhecimento completo em circunstÃncias ideais. Em situaÃÃes reais, nas quais o conhecimento à parcial, a LÃgica de Primeira Ordem nÃo à suciente. LÃgicas nÃo-monotÃnicas tÃm sido propostas para melhor lidar com o raciocÃnio prÃtico. Uma formalizaÃÃo do raciocÃnio nÃo-monotÃnico bem-sucedida à a LÃgica Default de Reiter que estende a LÃgica de Primeira Ordem com regras default. Infelizmente, a LÃgica Default à indecidÃvel. Nesta dissertaÃÃo, propomos uma LÃgica de DescriÃÃo Default expressiva o suciente para formalizar o raciocÃnio prÃtico sobre bases de conhecimento. Ela tem como base monotÃnica a LÃgica de DescriÃÃo ALC. Adicionamos algumas restriÃÃes à aplicaÃÃo dos defaults a m de obter propriedades interessantes, tais como a coerÃncia e a eliminaÃÃo de extensÃes anÃmalas. Apresentamos os principais algoritmos usados para construir uma extensÃo com um passo-a-passo e suas anÃlise de complexidade. / Knowledge formalization and reasoning automatization are central within Articial Intelligence. First Order Logic has been traditionally used for such purposes. However, it is better suited to deal with complete knowledge in ideal circumstances. In real situations, in which the knowledge is partial, First Order Logic is not sucient. Nonmonotonic logics have been proposed to better cope with practical reasoning. A successful formalization of nonmonotonic reasoning is the Reiter's default logic which extends classical logic with default rules. Unfortunately, default logic is undecidable. In this work, we propose a description default logic expressible enough to formalize practical reasoning in knowledge bases. It has as its monotonic basis the ALC Description Logic. We add some restrictions to the application of defaults in order to obtain nice properties such as coherence and the elimination of anomalous extensions. We present the main algorithms used to build an extension with a step by step complexity analysis.

The main purpose of this paper is to provide evidence of financial leverage, liquidity, profitability, and firm size ability to predict bankruptcy of Swedish small and medium-sized enterprises (SMEs), and to create a bankruptcy prediction model for Swedish SMEs. The sample consists of 1086 Swedish SMEs, among which 543 did go bankrupt between 2015 and 2019. The paper employs logistic regression and Mann-Whitney U-test to test the hypotheses. The independent variables are derived from previous research and further filtered in a selection process, resulting in a final set of six variables. Financial leverage, liquidity, profitability, and firm size is found to have significantly predictive abilities to determine SME bankruptcy. The model has an overall classification accuracy of 77.6% out-of-sample and is able to classify 82.2% of the bankruptcies correctly out-of-sample.

In July 2014, Argentina entered selective default, even as the country remained financially solvent. The default stemmed not from economic woes, but rather from protracted international litigation between Argentina and a group of hedge funds who, for years, refused to negotiate with Argentina over their bond holdings in the wake of the country’s first default in 2001. These holdouts stalled negotiations and locked Argentina out of international credit markets, damaging the country’s economy and financially harming other creditors and Argentinian citizens alike. Argentina ended up in such a dilemma because of the current sovereign debt restructuring process. No international arbitrator of sovereign debt currently exists. Instead, a country must negotiate with creditors on an ad-hoc basis, gathering support from 100% of creditors before it can restructure its debt and reenter international credit markets, an extremely inefficient system. This paper will assess the current system of sovereign default renegotiations, identifying inefficiencies in the current system, reviewing past proposals for improvements to the system, and ultimately proposing an international arbitrator for default negotiations. This text uses the development of the US Federal Municipal Bankruptcy Act of 1934 as a guide for an international bankruptcy court. Prior to the passage of the law, municipalities faced many of the same challenges faced by defaulted nations today, including powerful holdouts and a lack of structure in the negotiation system. Given the similarities between the two cases, the Federal Municipal Bankruptcy Act serves as an ideal framework for sovereign default arbitration internationally.

published_or_final_version / Law / Master / Master of Philosophy

This work develops some simple models to study risky corporate debt using first passage-time approach. Analytical valuation expression derived from different models as functions of firm’s values and the short-term interest rate with time-dependent parameters governing the dynamics of the firm values and interest rate. We develop some numerical approximation of the analytical valuation, which is given implicitly through Voltera integral equation related to the density of the first-passage- time that a firm reaches some specified default barrier. For some appropriate default barrier arising from financial considerations we obtain a closed-form solution, which is more flexible for numerical calculation.

Master of Agribusiness / Department of Agricultural Economics / Allen M. Featherstone / Institutions within the Farm Credit System (FCS) make risk-based lending decisions. As a primary lender to agriculture, these decisions are based on qualitative and quantitative procedures based on guidelines created for the purpose of measuring financial risk or the future probability that a loan will be in default of full repayment. As the risk increases, the cost to the FCS institution also increases to support a higher risk, higher probability of delinquency. Concentration risk, intrinsic risk, transaction risk, repayment risk, reputation risk are just a few examples of risk-based lending decisions. Under regulatory direction, FCS institutions have a charter to provide financing to agriculture’s food and fiber industries. The forest products industry is a large commodity borrower of risk-based financing within the FCS, specifically in the Pacific Northwest. Among other commodities, Northwest Farm Credit Services (Northwest FCS) supports the forest products industry through financial lending products. A majority of agricultural commodities reflect cycles of robust earnings and weak profits based on macro- and micro-economic indicators. The United States forest products industry had a period of strong earnings based primarily on the housing bubble between 2002-2007. With the U.S. economic recession beginning in 2008, the forest products industry also waned from 2008-2012. This impact resulted in financial stress for many forest product companies, both nationally and internationally. Due to the downturn in the forest products industry, regulators were quick to position the industry with high risk-based assumptions, thus putting pressure to Northwest FCS’ risk-guidelines in supporting that historical analysis accurately depicted industry risk. The purpose of this thesis is threefold: to study the correlation between different major commodity groups to better understand the value of a commodity concentration limit as a way to mitigate portfolio risk for Northwest FCS; to support analysis used by Northwest FCS and their ability to calculate the likelihood of financial stress; and provide customer-based feedback by way of a survey from forest products companies in the industry, as additional support to assumptions that were used to calculate certain subjective criteria for estimating risk. As one method to analyze financial risk, customer data was collected for the years ending 12/31/2008, 12/31/2011, and 12/31/2014. Statistical regression analysis was used to measure financial stress migration based on companies in the forest products industry. The regression analysis indicates financial measures of liquidity, leverage, and cash flow used for such calculated stress, specifically prior to the economic downturn of 2008, through the downturn of 2008-2012, and post-recovery of the forest products industry are correlated with measuring financial risk. As a risk mitigation tool, the board of directors that governs Northwest FCS hold a commodity concentration limit of fifteen percent (15%) for the forest products industry. The customer survey provided information that allowed Northwest FCS to create subjective rating criteria for calculating risk. A guideline was created to assess subjective criteria provided by forest products customers on the same level based on the feedback provided which may be beneficial for understanding current results and potential future subjective risk associated within the industry.