The problem of knowledge evolution has received considerable attention over the years. Mainly, the study of the dynamics of knowledge has been addressed in the area of Belief Revision, a field emerging as the convergence of the efforts in Philosophy, Logic, and more recently Computer Science, where research efforts usually involve “flat” knowledge bases where there is no additional information about the formulas stored in it. Even when this may be a good fit for particular applications, in many real-world scenarios (...) different information items may be attached to formulas. For instance, when the reliability of the source of the piece of information is attached to it as a measure of some quality (e.g., strength) of the piece of information itself, or when some characteristic informs us on the desirability of the item (e.g., the potential benefit that could be obtained from it). If this type of information is available, we can use it to guide how the belief base is to be modified when new information arrives. In this work, we present a novel approach to the contraction of knowledge bases where formulas have values attached that measure some quality linked to those formulas, exploiting it to define their desirability, and uses such desirability to define which formulas need to be removed to solve conflicts. In this context, we introduce a set of properties for contraction operators by extending classic approaches. We also show how the local treatment of minimal conflicts can induce some counter-intuitive contractions, and we present a way to avoid them by considering optimal resolutions of conflicts using the additional information encoded. We show how the proposed formalization captures any contraction that is optimal under a set of features. Finally, we present a refinement based on the identification of related minimal conflicts that performs contraction in optimal ways without looking into the entire knowledge base. The approach is based on the use of the accrual of beliefs where several formulas collaboratively use their respective values to prevail in the resolution of conflicts. (shrink)

Sven-Ove Hansson and Erik Olsson studied in [7] the logical properties of an operation of contraction first proposed by Isaac Levi in [10]. They provided a completeness result for the simplest version of contraction that they call Levicontraction but left open the problem of characterizing axiomatically the more complex operation of value-based contraction or saturatable contraction. In this paper we propose an axiomatization for this operation and prove a completeness result for it. We argue that the (...) resulting operation is better behaved than various rival operations of contraction defined in recent years. (shrink)

One way to construct a contraction operator for a theory (belief set) is to assign to it a base (belief base) and an operator of partial meet contraction for that base. Axiomatic characterizations are given of the theory contractions that are generated in this way by (various types of) partial meet base contractions.

In the most common approaches to belief dynamics, states of belief are represented by sets that are closed under logical consequence. In an alternative approach, they are represented by non-closed belief bases. This representation has attractive properties not shared by closed representations. Most importantly, it can account for repeated belief changes that have not yet been satisfactorily accounted for in the closed approach.

Sven-Ove Hansson and Erik Olsson studied in Hansson and Olsson, 103–119 1995) the logical properties of an operation of contraction first proposed by Isaac Levi in Levi. They provided a completeness result for the simplest version of contraction that they call Levi-contraction but left open the problem of characterizing axiomatically the more complex operation of value-based contraction or saturatable contraction. In this paper we propose an axiomatization for this operation and prove a completeness result for (...) it. We argue that the resulting operation is better behaved than various rival operations of contraction defined in recent years. (shrink)

We introduce a class of set-theoretic operators on a tolerance space that models the process of minimal belief contraction, and therefore a natural process of iterated contraction can be defined. We characterize the class of contraction operators and study the properties of the associated iterated belief contraction.

Expect for formal contracts, there are informally unwritten psychological contracts in the relationship between buyer and supplier for construction projects. The PC can affect the construction project performance and even cause project failure, but its process and formation are complex and not comprehensive in existing researches. This paper analyzes the PC between buyer and supplier by using evolutionary game and repeated game to tackle this gap. The results show the following: the goodwill and interest have an important impact on PC (...) fulfillment. The PC is vulnerable; for example, once either one fails to perform PC, the other will also destroy PC, and then the construction project will enter a vicious circle. In the process of repeated game, the effect of goodwill will gradually disappear, and the interest will play a major role. If the project performance is only linked to one participant, it will lead to breach from another player. Some measures may help both sides to complete PC, such as making both sides profitable, increasing the emphasis on business reputation, and improving the relevance of construction projects performance. (shrink)

We propose a new class of multiple contraction operations — the system of spheres-based multiple contractions — which are a generalization of Grove’s system of spheres-based (singleton) contractions to the case of contractions by (possibly non-singleton) sets of sentences. Furthermore, we show that this new class of functions is a subclass of the class of the partial meet multiple contractions.

In this article we present a new class of multiple contraction functionswhich are a generalization of the epistemic entrenchment-based contractions (Grdenfors & Makinson, 1988) to the case of contractions by (possibly nonsingleton) sets of sentences and provide an axiomatic characterization for that class of functions. Moreover, we show that the class of epistemic entrenchment-based multiple contractions coincides with the class of system of spheres-based multiple contractions introduced in Fermé & Reis (2012).

On the one hand, the absence of contraction is a safeguard against the logical (property theoretic) paradoxes; but on the other hand, it also disables inductive and recursive definitions, in its most basic form the definition of the series of natural numbers, for instance. The reason for this is simply that the effectiveness of a recursion clause depends on its being available after application, something that is usually assured by contraction. This paper presents a way of overcoming this (...) problem within the framework of a logic based on inclusion and unrestricted abstraction, without any form of extensionality. (shrink)

To improve the value of pharmaceutical spending, some manufacturers and payers have introduced outcomes-based contracts, where rebates are tied to specified outcomes. We reviewed the literature and interviewed key experts to assess these contracts' potential to slow pharmaceutical spending. We found that while outcomes-based contracts are increasingly common in the US, they are still limited by multiple factors — including the lack of meaningful outcomes data. Moreover, there is no evidence to date that they slow pharmaceutical spending or increase access. (...) Experts favored having CMS test and rigorously evaluate this model to achieve a better understanding of the implications. (shrink)

The dynamic nature and increasing complexity of the construction industry have led to increased conflicts in construction projects. An accurate prediction of the outcome of a dispute resolution in courts could effectively reduce the number of disputes that would otherwise conclude by spending more money through litigation. This study aims to introduce a two-layered fuzzy logic model for predicting court decisions in construction contract disputes. 100 cases of construction contract disputes are selected from the courts of Iran. A questionnaire survey (...) is then conducted to extract a set of fuzzy rules for identifying important decision parameters and expert knowledge. Accordingly, a two-layered fuzzy logic-based decision-making architecture is proposed for the prediction model. Furthermore, the fuzzy system is trained based on 10-fold cross-validation. Analysis of results indicates that 51 out of the 100 cases are filed after the dissolution and termination of the contract show a significant impact of these clauses as the root cause in construction contract disputes. Our results present a proposed hierarchical fuzzy system that can correctly predict nearly 60% of the test data. Also, we demonstrate a methodology of using argument before ML to establish interpretable AI models. Based on our findings, a fuzzy model with a hierarchical structure may be used as a simple and efficient method for predicting court decisions in construction contract disputes. (shrink)

This paper proposes an innovative approach to achieving real-time polymorphic behavior detection, and its direct application to blockchain-focused smart-contracts. We devise a method based on a non-deterministic finite state machine to perform approximate pattern-matching, using a look-ahead mechanism implemented through a concept similar to that of a sliding window, and using threshold-based similarity checking at every state in the automaton. We introduce and formalize our approach, discuss the challenges we faced and then test it in a real-world environment. The experimental (...) results obtained showed a significant speed-up of our approach, as compared to the classic similarity measures used commonly in such scenarios. (shrink)

As the rising costs of lifestyle-related diseases place increasing strain on public healthcare systems, the individual’s role in disease may be proposed as a healthcare rationing criterion. Literature thus far has largely focused on retrospective responsibility in healthcare. The concept of prospective responsibility, in the form of a lifestyle contract, warrants further investigation. The responsibilisation in healthcare debate also needs to take into account innovative developments in mobile health technology, such as wearable biometric devices and mobile apps, which may change (...) how we hold others accountable for their lifestyles. Little is known about public attitudes towards lifestyle contracts and the use of mobile health technology to hold people responsible in the context of healthcare. This paper has two components. Firstly, it details empirical findings from a survey of 81 members of the United Kingdom general public on public attitudes towards individual responsibility and rationing healthcare, prospective and retrospective responsibility, and the acceptability of lifestyle contracts in the context of mobile health technology. Secondly, we draw on the empirical findings and propose a model of prospective intention-based lifestyle contracts, which is both more aligned with public intuitions and less ethically objectionable than more traditional, retrospective models of responsibility in healthcare. (shrink)

Since e-Commerce has become a discipline, e-Contracts are acknowledged as the tools that will assure the safety and robustness of the transactions. A typical e-Contract is a binding agreement between parties that creates relations and obligations. It consists of clauses that address specific tasks of the overall procedure which can be represented as workflows. Similarly to e-Contracts, Intelligent Agents manage a private policy, a set of rules representing requirements, obligations and restrictions, additionally to personal data that meet their user’s interests. (...) In this context, this study aims at proposing a policy-based e-Contract workflow management methodology that can be used by semantic web agents, since agents benefit from Semantic Web technologies for data and policy exchanges, such as RDF and RuleML that maximize interoperability among parties. Furthermore, this study presents the integration of the above methodology into a multi-agent knowledge-based framework in order to deal with issues related to rules exchange where no common syntax is used, since this framework provides reasoning services that assist agents in interpreting the exchanged policies. Finally, a B2C e-Commerce scenario is presented that demonstrates the added value of the approach. (shrink)

This paper reorganizes and further develops the theory of partial meet contraction which was introduced in a classic paper by Alchourron, Gardenfors, and Makinson. Our purpose is threefold. First, we put the theory in a broader perspective by decomposing it into two layers which can respectively be treated by the general theory of choice and preference and elementary model theory. Second, we reprove the two main representation theorems of AGM and present two more representation results for the finite case (...) that "lie between" the former, thereby partially answering an open question of AGM. Our method of proof is uniform insofar as it uses only one form of "revealed preference", and it explains where and why the finiteness assumption is needed. Third, as an application, we explore the logic characterizing theory contractions in the finite case which are governed by the structure of simple and prioritized belief bases. (shrink)

Very diverse societies pose real problems for Rawlsian models of public reason. This is for two reasons: first, public reason is unable accommodate diverse perspectives in determining a regulative ideal. Second, regulative ideals are unable to respond to social change. While models based on public reason focus on the justification of principles, this book suggests that we need to orient our normative theories more toward discovery and experimentation. The book develops a unique approach to social contract theory that focuses on (...) diverse perspectives. It offers a new moral stance that author Ryan Muldoon calls, "The View From Everywhere," which allows for substantive, fundamental moral disagreement. This stance is used to develop a bargaining model in which agents can cooperate despite seeing different perspectives. Rather than arguing for an ideal contract or particular principles of justice, Muldoon outlines a procedure for iterated revisions to the rules of a social contract. It expands Mill's conception of experiments in living to help form a foundational principle for social contract theory. By embracing this kind of experimentation, we move away from a conception of justice as an end state, and toward a conception of justice as a trajectory. (shrink)

Blockage contraction is an operation of belief contraction that acts directly on the outcome set, i.e. the set of logically closed subsets of the original belief set K that are potential contraction outcomes. Blocking is represented by a binary relation on the outcome set. If a potential outcome X blocks another potential outcome Y, and X does not imply the sentence p to be contracted, then Y ≠ K ÷ p. The contraction outcome K ÷ p (...) is equal to the (unique) inclusion-maximal unblocked element of the outcome set that does not imply p. Conditions on the blocking relation are specified that ensure the existence of such a unique inclusion-maximal set for all sentences p. Blockage contraction is axiomatically characterized and its relations to AGM-style operations are investigated. In a finite-based framework, every transitively relational partial meet contraction is also a blockage contraction. (shrink)

Name der Zeitschrift: Studies in Logic, Grammar and Rhetoric Jahrgang: 45 Heft: 1 Seiten: 277-287.

We are very grateful to both Matthew Ratcliffe and Thomas Szasz for taking the time to read and respond to our paper. Ratcliffe is broadly sympathetic to our efforts and provides a very convincing argument against mind–body dualisms by drawing on work from the phenomenological tradition. His comments extend rather than challenge our central thesis. Szasz, however, is dismissive of our position. As a result, most of our response is directed to his commentary. Ratcliffe uses the work of van der (...) Berg to make the case that any easy distinction between bodily and mental illness or suffering is false to our lived reality as human beings. Of course, in the day-to- day world of contemporary medical practice .. (shrink)

This book examines the most controversial issues concerning the use of pre-drafted clauses in fine print, which are usually included in consumer contracts and presented to consumers on a take-it-or-leave-it basis. By applying a multi-disciplinary approach that combines consumer's psychology and seller's drafting power in the logic of efficiency and good faith, the book provides a fresh and unconventional analysis of the existing literature, both theoretical and empirical. Moving from the unconscionability doctrine, it criticizes (and in some cases refutes) its (...) main conclusions based on criteria which are usually invoked to sustain the need for public intervention to protect consumers, and specifically related to Law (contract complexity), Psychology (consumer lack of sophistication criterion) and Economics (market structure criterion). It also analyzes the effects of different regulations, such as banning vexatious clauses or mandating disclosure clauses, showing that none of them protect consumers, but in fact prove to be harmful when consumers are more vulnerable, that is whenever sellers can exploit some degree of market power. In closing, the book combines these disparate aspects, arguing that the solution (if any) to the problem of consumer exploitation and market inefficiency associated with the use of contracts of adhesion in these contexts cannot be found in removing or prohibiting hidden clauses, but instead has to take into account the effects of these clauses on the contract as a whole. (shrink)

The intention of the article is to offer stakeholders affected by mergers a criterion from which moral arguments may be generated for the organization of each individual case. The criterion: "Any operation causing legitimate interests to suffer vital infringement should be avoided in a merger process." A vital infringement of these interests is assumed when the merger undermines unique positive opportunities or considerable impairment in the future, impossible to overcome for the person affected without an unacceptable level of difficulty. Therefore, (...) we mainly concentrate on implicit contracts – which should be based on the principle pacta sunt servanda as well. These contracts are mandatory to run an economy that produces increasingly more knowledge-based goods. (shrink)

How robust is a contraction-free approach to the semantic paradoxes? This paper aims to show some limitations with the approach based on multiplicative rules by presenting and discussing the significance of a revenge paradox using a predicate representing an alethic modality defined with infinitary rules.

This chapter contains sections titled: Introduction The Challenge to the Distinctiveness and the Coherence of Contract Four Autonomy‐Based Theories Three Teleological Theories Concluding Remarks References.

The basic assumption of repertoire contraction is that only some of the logically closed subsets of the original belief set are viable as contraction outcomes. Contraction takes the form of choosing directly among these viable outcomes, rather than among cognitively more far-fetched objects such as possible worlds or maximal consistent subsets of the original belief set. In this first investigation of repertoire contraction, postulates for various variants of the operation are introduced. Necessary and sufficient conditions are (...) given for when repertoire contraction coincides with AGM contraction or with operations generated by AGM-style contraction on a belief base. A close connection is shown to hold between repertoire contraction and specified meet contraction. (shrink)

The contemporary political philosopher John Rawls considers himself to be part of the social contract tradition of John Locke, Jean-Jacques Rousseau and Immanuel Kant, but not of the tradition of Locke's predecessor, Thomas Hobbes. Call the Hobbesian tradition interest-based, and the Lockean tradition right-based, because it assumes that there are irreducible moral facts which the social contract can assume. The primary purpose of Locke's social contract is to justify the authority of the state over its citizens despite the fact that (...) those citizens are naturally free and equal. I assume that this task is of central importance to all right-based social contract theories: in chapter one I lay out the general problems faced by all contract theories, and in chapter two, three and four I examine in depth the accounts of political obligation offered by Locke, Rousseau, and Rawls. I conclude that all members of the right-based social contract tradition fail to provide an account of obligation that can explain the bond between a citizen and her state. (shrink)

As the contract cheating market has become more sophisticated and competition has intensified, the contract cheating industry has had to redevelop its approach to gain custom. The industry has developed new models of internal operation and providers are using more sophisticated techniques to reach potential customers. This paper discusses contract cheating industry workflows and introduces terminology to allow complexities of the industry to be more consistently discussed. Examples are provided throughout to indicate the scale and challenge of the contract cheating (...) industry operations.An analysis of contract cheating operations on the micro-outsourcing website Fiverr.com is presented, using comparative data collected in June 2016 and October 2018. The analysis of the data demonstrates how the contract cheating industry is seeing continual change. Specifically, on Fiverr.com, this includes an increase in the number of providers offering essay writing services, particularly those from Kenya and Pakistan. The increase in service availability is accompanied by an associated reduction in essay pricing. The advertised pricing per 1000 words has dropped substantially, from $31.73 USD to $5.73 USD. The accounts used by contract cheating providers are also being replaced at an increased rate.Based on the data, contract cheating providers on Fiverr.com are currently estimated to be taking a minimum of $92,001 USD per year in revenue. This is an example calculated from only one search term on which contract cheating providers advertise on only one micro-outsourcing site used for contract cheating. The actual industry income from micro-outsourcing web sites is likely to be substantially higher. (shrink)

In this paper, we consider multiplicative-additive fragments of affine propositional classical linear logic extended with n-contraction. To be specific, n-contraction (n 2) is a version of the contraction rule where (n+ 1) occurrences of a formula may be contracted to n occurrences. We show that expansions of the linear models for (n + 1)- valued ukasiewicz logic are models for the multiplicative-additive classical linear logic, its affine version and their extensions with n-contraction. We prove the finite (...) axiomatizability for the classes of finite models, as well as for the class of infinite linear models based on the set of rational numbers in the interval [0, 1]. The axiomatizations obtained in a Gentzen-style formulation are equivalent to finite and infinite-valued ukasiewicz logics. (shrink)

Abstract:Social contracting has a long and important place in the history of political philosophy (Hardin, 1991; Waldron, 1989) and as a theory of justice (Baynes, 1989; Rawls, 1971). More recently, it has been developed into an individual rights-based theory of organizations (Keeley, 1980, 1988), and as a way to integrate ethics and moral legitimacy into corporate strategy and action (Donaldson, 1982; Freeman&Gilbert, 1988). Currently, it is being proposed as an integrative theory of economic ethics (Donaldson&Dunfee, forthcoming). This paper will extend (...) the Donaldson and Dunfee approach by arguing thatsocial contracting can best be understood and applied in organizational settings if it is perceived and treated as a network governance process. This insight can benefit management scholars and practitioners alike, since it calls attention to the processes by which trust is created and sustained in on-going contractual relationships. It also strongly suggests that a new approach to applying managerial discretion, asmoral agency, is needed to realize the full competitive and ethical potential of emerging network forms. (shrink)

Contractions on belief sets that have no finite representation cannot be finite in the sense that only a finite number of sentences is removed. However, such contractions can be delimited so that the actual change takes place in a logically isolated, finite-based part of the belief set. A construction that answers to this principle is introduced, and is axiomatically characterized. It turns out to coincide with specified meet contraction.

The postulate of recovery is commonly regarded to be the intuitively least compelling of the six basic Gärdenfors postulates for belief contraction. We replace recovery by the seemingly much weaker postulate of core-retainment, which ensures that if x is excluded from K when p is contracted, then x plays some role for the fact that K implies p. Surprisingly enough, core-retainment together with four of the other Gärdenfors postulates implies recovery for logically closed belief sets. Reasonable contraction operators (...) without recovery do not seem to be possible for such sets. Instead, however, they can be obtained for non-closed belief bases. Some results on partial meet contractions on belief bases are given, including an axiomatic characterization and a non-vacuous extension of the AGM closure condition. (shrink)

The supply chain in the new retail context demands higher requirements on the price, service, and logistics level. It is very important to seek the coordination among the optimal price, service level, and logistics level. In this paper, we propose the coordination of pricing, the service level, and delivery time of a new retail supply chain composed of one product supplier, one platform service provider, and one logistics provider. Firstly, the profit function mode of product pricing, platform service level, and (...) logistics distribution level that influence the consumers’ demand is constructed in two modes, namely, the centralized and decentralized decision mode. Then, we calculate and compare the optimal product price, the optimal platform service level, the optimal delivery time, and the profit of each member of the supply chain from both decision modes. We discovered that cooperation improves the service level, logistics level, and the income of each member of the new retail supply chain. Therefore, we propose a novel mode called the coordination mode as a strategy for the supply chain based on the combination contract. We performed a numerical analysis to demonstrate the feasibility and effectiveness of the coordination contract. (shrink)

Modern belief revision theory is based to a large extent on partial meet contraction that was introduced in the seminal article by Carlos Alchourrón, Peter Gärdenfors, and David Makinson that appeared in 1985. In the same year, Alchourrón and Makinson published a significantly different approach to the same problem, called safe contraction. Since then, safe contraction has received much less attention than partial meet contraction. The present paper summarizes the current state of knowledge on safe (...) class='Hi'>contraction, provides some new results and offers a list of unsolved problems that are in need of investigation. (shrink)

Contract theories may be a useful analytical tool for understanding and explaining contract, as well as for facilitating orientation in a complex and often fragmented legal regulation. The article presents main understandings of contract in various European jurisdictions: contract as free assumption of obligation, contract as a bargain based on the idea of consideration, contract as free assumption of obligation based on sufficient causa. The article inquires as to how universal those theories are, what are the recent trends in the (...) development of European contract law, what philosophy of contract underlies the soft law instruments, such as UNIDROIT Principles of International Commercial Contracts or Principles of European Contract Law (PECL), what is the stance of the Draft Common Frame of Reference (DCFR) in regard to the concept of contract. Under the law of Lithuania the definition of contract comprises elements found in several European countries, but it is argued that the new Lithuanian Civil Code has not received any model in its pure form. However it seems that the prevailing view understands contract as juridical act, as freely assumed obligation and meeting of parties’ intentions with the aim to create legal effects. Following the position of soft law instruments in regard to the elements of the contract, Lithuanian law (at least in its statutory form) does not have any explicit additional requirements, such as consideration or causa. (shrink)

This paper applies Wempe’s (2005, Business Ethics Quarterly 15(1), 113–135) boundary conditions that define the external and internal logics for contractarian business ethics theory, as a system of argumentation for evaluating current or prospective institutional arrangements for arriving at the “good life,” based on the principles and practices of social justice. It does so by showing that a more dynamic, process-oriented, and pluralist ‘dialogic twist’ to Donaldson and Dunfee’s (2003, ‘Social Contracts: sic et non’, in P. Heugens, H. van Oosterhout (...) and J. Vromen (eds.), The Social Institutions of Capitalism: Evolution and Design of Social Contracts (Cheltenham, UK, Edward Elgar Publishing, Ltd.) pp. 109–126; 1999, Ties that Bind: A Social Contracts Approach to Business Ethics (Boston, MA, Harvard Business School Press); 1995, Economics and Philosophy 11(1), 85–112; 1994, Academy of Management Review 19(2), 252–284.) integrated social contracting theory (ISCT) of economic ethics will further develop this promising and influential approach to moral reasoning, ethical decision-making, and stakeholder governance. This evolutionary, interactive learning-based model of ethical norm generation via dialogic stakeholder engagement is particularly appropriate within economic communities that are experiencing value conflict and pressures for institutional change. (shrink)

A number of the most influential presentations of normative stakeholder theory are based upon an economic model of the firm as a nexus of contracts. In this paper I argue that the use of such a model to address moral issues is both logically and practically problematic and effectively undermines the stakeholder position. I then sketch out the key characteristics of an alternative, social relationships model of the firm, and show how this might provide a basis for the development of (...) a more relevant and robust version of normative stakeholder theory than has hitherto been proposed. (shrink)

A model of coherentist belief contraction is constructed. The outcome of belief contraction is required to be one of the coherent subsets of the original belief set, and a set of plausible properties is proposed for this set of coherent subsets. The contraction operators obtained in this way are shown to coincide with well-known belief base operations. This connection between coherentist and "foundationalist" approaches to belief change has important implications for the philosophical interpretation of models of (...) belief change. (shrink)

A number of the most influential presentations of normative stakeholder theory are based upon an economic model of the firm as a nexus of contracts. In this paper I argue that the use of such a model to address moral issues is both logically and practically problematic and effectively undermines the stakeholder position. I then sketch out the key characteristics of an alternative, social relationships model of the firm, and show how this might provide a basis for the development of (...) a more relevant and robust version of normative stakeholder theory than has hitherto been proposed. (shrink)

Semi-contraction is a withdrawal operation defined by Fermé in "On the logic of theory change: Contraction without recovery." In this paper we propose: (1) an axiomatic characterization of semi-contraction; (2) an alternative construction for semi-contraction based on semi-saturatable sets, inspired by Levi's saturatable sets; (3) a special kind of semi-contraction that satisfies the Lindström and Rabinowicz interpolation thesis.

In this paper we study AGM contraction and revision of rules using input/output logical theories. We replace propositional formulas in the AGM framework of theory change by pairs of propositional formulas, representing the rule based character of theories, and we replace the classical consequence operator Cn by an input/output logic. The results in this paper suggest that, in general, results from belief base dynamics can be transferred to rule base dynamics, but that a similar transfer of AGM (...) theory change to rule change is much more problematic. First, we generalise belief base contraction to rule base contraction, and show that two representation results of Hansson still hold for rule base contraction. Second, we show that the six so-called basic postulates of AGM contraction are consistent only for some input/output logics, but not for others. In particular, we show that the notorious recovery postulate can be satisfied only by basic output, but not by simple-minded output. Third, we show how AGM rule revision can be defined in terms of AGM rule contraction using the Levi identity. We highlight various topics for further research. (shrink)

Based on the assumption that the long-term value of a venture capital satisfies the algebraic Brownian motion, we develop a continuous-time exit model of venture capital under different exit modes, namely, initial public offering and mergers and acquisitions. The employee incentive problem is analyzed jointly with the exit decision of the firm in terms of the exit timing and the exit mode. Further, the problem of capital exit is considered from two perspectives, namely, optimal venture capital and social welfare maximization, (...) and the differences between these exit decisions are compared. Our model predicts that the timing of an IPO, the purpose of which is to maximize the utility of the capitalists, lags behind the exit timing, whose purpose is to maximize social welfare. Using a numerical analysis, this paper also proves that increasing the production efficiency, lowering the interest rates, and improving risk management can make the exit decision of venture capitalists converge with that of maximizing social welfare. (shrink)

A representation theorem is obtained for contraction operators that are based on Levi's recent proposal that selection functions should be applied to the set of saturatable contractions, rather than to maximal subsets as in the AGM framework. Furthermore, it is shown that Levi's proposal to base the selection on a weakly monotonic measure of informational value guarantees the satisfaction of both of Gärdenfors' supplementary postulates for contraction. These results indicate that Levi has succeeded in constructing a well-behaved (...) operation of contraction that does not satisfy the postulate of recovery. (shrink)

In this paper we study AGM contraction and revision of rules using input/output logical theories. We replace propositional formulas in the AGM framework of theory change by pairs of propositional formulas, representing the rule based character of theories, and we replace the classical consequence operator Cn by an input/output logic. The results in this paper suggest that, in general, results from belief base dynamics can be transferred to rule base dynamics, but that a similar transfer of AGM (...) theory change to rule change is much more problematic. First, we generalise belief base contraction to rule base contraction, and show that two representation results of Hansson still hold for rule base contraction. Second, we show that the six so-called basic postulates of AGM contraction are consistent only for some input/output logics, but not for others. In particular, we show that the notorious recovery postulate can be satisfied only by basic output, but not by simple-minded output. Third, we show how AGM rule revision can be defined in terms of AGM rule contraction using the Levi identity. We highlight various topics for further research. (shrink)

Organ transplantation has become a proven, cost-effective lifesaving treatment, but its promise is contingent on the number of available organs. The growing gap between the demand and supply results in unnecessary loss and diminished quality of life as well as high costs for surviving patients and health insurers. Twenty years after the enactment of the National Organ Transplantation Act, it is time to rethink the moral basis and overall design of organ transplantation policy. We propose a national plan for organ (...) transplantation insurance under which the federal government would assume responsibility for increasing the organ supply and would cover all costs associated with transplantation for patients not otherwise covered. (shrink)