Harder Cases Research Articles

A novel structure-exploiting encoding for SAT-based diagnosis

ABSTRACT When a circuit exhibits abnormal behaviour, a diagnosis of the circuit is a set of gates whose failure explains the abnormality. The cardinality of a diagnosis is the number of gates assumed to be failing. A diagnosis is of minimum cardinality if no other diagnosis of the circuit exists that has a smaller cardinality. In general, the number of diagnoses can be exponentially large, and often only a preferred set of minimum-cardinality diagnoses is computed. In propositional satisfiability (SAT), given a propositional circuit, the task is to check whether all gates of the circuit can be assigned values in a consistent manner. In SAT-based diagnosis approach, the given circuit is injected with additional circuitry modelling the health of gates as well as the cardinality constraint. Under an abnormal observation the SAT solver repeatedly computes consistent assignments to all gates in the augmented circuit where each such assignment corresponds to a minimum-cardinality diagnosis. However, diagnosis of large size circuits as well as diagnostic cases with large minimum cardinalities pose a challenge for SAT solvers. To scale diagnosis to larger and harder cases, we propose a novel encoding that captures the hierarchical structure of the circuit in terms of single-output self-contained sub-circuits called cones. Cones have been exploited in diagnostic reasoning in the past; however, our encoding is the first of its kind in a SAT-based approach. Previously, cones were used to take the abstraction of a circuit and simplify it, while we exploit cones to improve the speed and efficiency of the SAT solver. Experiments on 1800 diagnostic cases of ISCAS-85 benchmark circuits show that the new encoding allows faster and more scalable diagnosis solving 1700 cases which is 163 more than the number of cases solved by the baseline approach.

Orthohantavirus Spp. – Review Of Genus

Abstract The infections caused by orthohantaviruses were already known in the Middle Ages as “English sweats.” There are two main diseases caused by these viruses – HPS (hantavirus pulmonary syndrome) and HFRS (hemorrhagic fever with renal syndrome). Rodents are the main reservoir of these microorganisms, and humans usually catch them by inhalation, as a result of contact with secretions and droppings of carriers. HPS is characterized by a sudden onset, and symptoms include primarily cough, fever and difficulty breathing, and in extreme cases – respiratory failure and cardiogenic shock. HFRS begins suddenly and the main manifestation includes fever, renal failure, hemorrhage, hematuria and proteinuria, as well as shock. At present, anti-hantavirus therapy with proven effectiveness does not exist. A key role in the treatment is resting lifestyle, electrolyte control, fluid therapy and prevention of hypotension, and in harder cases – administration of oxygen. Deviations from normal values in laboratory analyzes of people infected with this pathogen depend on the organ affected by the disease process 1. History 2. Systematics of Orthohantavirus spp. genus 3. Morphology 3.1. Genome 3.2. Structure of the virion 4. Mechanism of infection 4.1. Route of infection 4.2. Life cycle 5. Pathogenicity 6. Treatment 7. Diagnostics 8. Prevention – vaccines 9. Summary

Some Enumeration Problems on Central Configurations at the Bifurcation Points

In “Counting central configurations at the bifurcation points,” we proposed an algorithm to rigorously count central configurations in some cases that involve one parameter. Here, we improve our algorithm to consider three harder cases: the planar $(3+1)$ -body problem with two equal masses; the planar 4-body problem with two pairs of equal masses which have an axis of symmetry containing one pair of them; the spatial 5-body problem with three equal masses at the vertices of an equilateral triangle and two equal masses on the line passing through the center of the triangle and being perpendicular to the plane containing it. While all three problems have been studied in two parameter cases, numerical observations suggest new results at some points on the bifurcation curves. Applying the improved version of our algorithm, we count at those bifurcation points. As a result, for the $(3+1)$ -body problem, we identify three points on the bifurcation curve where there are 8 central configurations, which adds to the known results of $8,9,10$ ones. For our 4-body case, at the bifurcation points, there are 3 concave central configurations, which adds to the known results of $2,4$ ones. For our 5-body case, at the bifurcation point, there is 1 concave central configuration, which adds to the known results of $0,2$ ones.

The value of a statistical life: some clarifications and puzzles

Many people have wondered why the US government conducts cost-benefit analysis with close reference to the value of a statistical life (VSL). It is helpful to answer that question by reference to the “Easy Cases,” in which those who benefit from regulatory protection must pay for it. In such cases, WTP is usually the right foundation for VSL, because beneficiaries are hardly helped by being forced to pay for regulatory protection that they believe not to be in their interests. In the Easy Cases, arguments from both welfare and autonomy support the use of WTP and VSL (with potentially important qualifications involving imperfect information and behavioral market failures). The analysis is less straightforward in harder cases, in which beneficiaries do not pay for all of the cost of what they receive (and may pay little of that cost). In such cases, arguments from welfare and autonomy might not lead in any clear direction. In the harder cases, regulation might be justified on welfare grounds even if the cost-benefit analysis (based on VSL) suggests that it is not. In principle, a direct inquiry into welfare (the master concept) would be preferable to use of cost-benefit analysis. In the harder cases, distributional considerations might also count in favor of proceeding (as prioritarianism suggests). But at the current time, direct inquiries into welfare consequences and into distributional effects are challenging in practice, and hence regulators should generally rely on cost-benefit analysis, making welfarist adjustments, or adjustments based on distributional considerations, only in compelling cases.

The Value of a Statistical Life: Some Clarifications and Puzzles

Many people have wondered why the US government conducts cost-benefit analysis with close reference to the value of a statistical life (VSL). It is helpful to answer that question by reference to the “Easy Cases,” in which those who benefit from regulatory protection must pay for it. In such cases, WTP is usually the right foundation for VSL, because beneficiaries are hardly helped by being forced to pay for regulatory protection that they believe not to be in their interests. In the Easy Cases, arguments from both welfare and autonomy support the use of WTP and VSL (with potentially important qualifications involving imperfect information and behavioral market failures). The analysis is less straightforward in harder cases, in which beneficiaries do not pay for all of the cost of what they receive (and may pay little of that cost). In such cases, arguments from welfare and autonomy might not lead in any clear direction. In the harder cases, regulation might be justified on welfare grounds even if the cost-benefit analysis (based on VSL) suggests that it is not. In principle, a direct inquiry into welfare (the master concept) would be preferable to use of cost-benefit analysis. In the harder cases, distributional considerations might also count in favor of proceeding (as prioritarianism suggests). But at the current time, direct inquiries into welfare consequences and into distributional effects are challenging in practice, and hence regulators should generally rely on cost-benefit analysis, making welfarist adjustments, or adjustments based on distributional considerations, only in compelling cases.

The Avoidance of Substance in Constitutional Rights

Avoidance, on the part of the judiciary, calls to mind a number of judicial postures. For Brian Ray, in his recent article “Evictions, Avoidance and the Aspirational Impulse” in South Africa’s Constitutional Court Review, avoidance signals an active posture of economic and social rights decision-making that limits the substantive development of constitutional doctrine, cedes to current legislation or policy the frame of rights analysis, and deliberately marginalizes the judicial role. While celebrating Ray’s ability to link disparate features of the South African Constitutional Court’s jurisprudence - the use of reasonableness review, the creation of new procedural remedies, the deployment of either extremely abstract constitutional deliberation or extremely fact-specific deliberation (without, Ray contends, the moderate use of either), and a tendency to find infringements of the obligations attached to economic and social rights only in the face of clearly unconstitutional conduct, with a retreat to deference in harder cases – this comment takes issue with the category of avoidance, and its corollary, of substance. It suggests that avoidance may offer too blunt a category for analysis, especially when extended to comparative assessments. In particular, Colombia, India and the United Kingdom offer features of economic and social rights jurisprudence that do very different things. Avoidance is best reserved to describe the many jurisdictions that still fail – judicially or legislatively - to recognize economic and social rights as law.

How the Sufficiency Minimum Becomes a Social Maximum

This article argues that, under likely empirical conditions, sufficientarianism leads not to an easily achievable duty to maintain a social minimum but to the onerous duty of maintaining a social maximum at the sufficiency level. This happens because sufficientarians ask us to give no weight at all to small benefits for people above the sufficiency level if the alternative is to relieve the suffering of people below it. If we apply this judgment in a world where there are rare diseases and hard-to-prevent accidents that cause people to fall below the sufficiency threshold, all of our discretionary spending will have to be devoted to bringing harder and harder cases up to sufficiency. Nothing will be left for anyone to consume above the sufficiency level.

Intuition and The Junctures of Judgment in Decision Procedures for Clinical Ethics

Moral decision procedures such as principlism or casuistry require intuition at certain junctures, as when a principle seems indeterminate, or principles conflict, or we wonder which paradigm case is most relevantly similar to the instant case. However, intuitions are widely thought to lack epistemic justification, and many ethicists urge that such decision procedures dispense with intuition in favor of forms of reasoning that provide discursive justification. I argue that discursive justification does not eliminate or minimize the need for intuition, or constrain our intuitions. However, this is not a problem, for intuitions can be justified in easy or obvious cases, and decision procedures should be understood as heuristic devices for reaching judgments about harder cases that approximate the justified intuitions we would have about cases under ideal conditions, where hard cases become easy. Similarly, the forms of reasoning which provide discursive justification help decision procedures perform this heuristic function not by avoiding intuition, but by making such heuristics more accurate. Nonetheless, it is possible to demand too much justification; many clinical ethicists lack the time and philosophical training to reach the more elaborate levels of discursive justification. We should keep moral decision procedures simple and user-friendly so that they will provide what justification can be achieved under clinical conditions, rather than trying to maximize our epistemic justification out of an overstated concern about intuition.

Cost‐Benefit Analysis and the Environment

This review-essay explores the uses and limits of cost-benefit analysis in the context of environmental protection, focusing on three recent books: Priceless, by Frank Ackerman and Lisa Heinzerling; Cellular Phones, Public Fears, and A Culture of Precaution, by Adam Burgess; and Catastrophe: Risk and Response, by Richard A. Posner. The review-essay emphasizes three principal limitations on the use of cost-benefit analysis. First, it is important to distinguish between the easy cases for cost-benefit analysis, in which the beneficiaries of regulation pay all or almost all of its cost, from the harder cases, in which the beneficiaries pay little for the environmental protection that they receive. In the harder cases, net welfare gains and distributional advantages are possible even if environmental regulation fails cost-benefit analysis. Second, there are possible uses, in the environmental context, of maximin rather than cost-benefit analysis, especially when regulators are attempting to control catastrophic risks where probabilities cannot be assigned. An Anti-Catastrophe Principle makes sense for such situations. Third, human beings are citizens, not merely consumers, and this point requires abandonment of the willingness to pay criterion in some contexts.

Cost-Benefit Analysis and the Environment

This review-essay explores the uses and limits of cost-benefit analysis in the context of environmental protection, focusing on three recent books: Priceless, by Frank Ackerman and Lisa Heinzerling; Cellular Phones, Public Fears, and A Culture of Precaution, by Adam Burgess; and Catastrophe: Risk and Response, by Richard A. Posner. The review-essay emphasizes three principal limitations on the use of cost-benefit analysis. First, it is important to distinguish between the easy cases for cost-benefit analysis, in which the beneficiaries of regulation pay all or almost all of its cost, from the harder cases, in which the beneficiaries pay little for the environmental protection that they receive. In the harder cases, net welfare gains and distributional advantages are possible even if environmental regulation fails cost-benefit analysis. Second, there are possible uses, in the environmental context, of maximin rather than cost-benefit analysis, especially when regulators are attempting to control catastrophic risks where probabilities cannot be assigned. An Anti-Catastrophe Principle makes sense for such situations. Third, human beings are citizens, not merely consumers, and this point requires abandonment of the willingness to pay criterion in some contexts.

Designing environmentally efficient services; a ‘script’ approach

The environmental performance of new sustainable service systems (3s) strongly depends on the actual use that is made of them. First of all, a new system must be able to recruit and keep clients, which implies that it should be easy to embed 3s in related household routines and values. Second, the service system should attract particularly those consumers who presently practice rather unsustainable behaviour, otherwise the savings may be low or even turn out to be negative. Third, the clients may appropriate the service and exhibit unintended use behaviour with unexpected and possibly negative environmental consequences. These arguments also hold true for products, but carry more weight in the case of service systems. Due to their complexity and potentially wide-ranging influence on household life, service systems are harder cases if possible rebound effects or problem shifts to other domains have to be foreseen and undercut by design. Because the design and organisation of a product or service can influence whether, by whom and how it will be used, an approach is suggested that can contribute to achieving a smart design, that is “scripted„ such that it encourages sustainable behaviour and discourages unsustainable behaviour. These issues are illustrated with examples from a sustainable Clothing Care service project. The proposed approach starts by studying current user behaviour including its underlying logic and values, and involves users in the iterative design process of the service system.

Perceptual Learning

The extent of adult improvement in not only complex but also simple perceptual tasks is remarkable. Although this phenomenon has been noted and studied since the middle of the 19th century, recent advances in the study of brain physiology and anatomy afford new insights. Improvement specificity suggests that changes involve early sensory cortical areas, previously thought to lose their plasticity following the first years. The critical role of selective attention, even in learning the simplest tasks, as well as the precedence of learning easy cases, suggests the involvement of high-level cortical areas. Learning easy cases is more general than learning difficult cases. This pattern suggests the involvement of both high- and low-level areas in an orderly manner, with easy learning beginning at high-level areas and harder cases being resolved by access to low-level areas. The mapping of behavioral findings to underlying brain sites provides a unified framework for this interdisciplinary field.

Algorithms in the public service

From time to time, one cannot escape the feeling that training ought to be a very simple process. Basically yon tell someone how to do a job and hope that he will remember what yon have told him. If he does, you can claim that the training was successful and represents money well spent; if he does not — well there may be many reasons for that. If the job is a difficult one, it is only natural to spend more time on training. If it contains a lot of unmemorable detail, the obvious answer is to tell the trainee all about the principles of the job and then get him to ‘sit by Nellie’ for a year or so. By now the complications are already setting in: you can bet that the first thing Nellie will tell him is that his training course was a lot of theoretical rubbish. Harder cases still are jobs which involve many procedures which are used only intermittently. Here one of the Nellies of the past Is sure to have written The Bible Of The System, containing a couple of hundred exceptions to exceptions. This usually frightens the trainee more than it helps him. Eventually, if the trainee is sufficiently motivated, he will qualify as a Nellie himself, which surely vindicates the method. Our training may look crazy, but it works.