SNePSwD: A newcomer to the SNePS family

Abstract

SNePS 2.1 is a knowledge representation and reasoning system that records the dependencies among propositions that are needed to perform a revision of beliefs when a contradiction is detected. The reasoning of SNePS 2.1 is based on a monotonic logic and the system has no provisos for performing an automatic revision of beliefs. In this paper we present SNePSwD that extends the capabilities of SNePS 2.1 along two dimensions: (1) it is able to represent default rules and to perform default reasoning, i.e. the logic underlying SNePSwD is non-monotonic; (2) it accepts the specification of preferences between hypotheses and uses them to decide which hypotheses to discard to resolve a contradiction. This latter possibility allows a semi-automatic contradiction resolution (in some cases, even completely automatic). We discuss the motivations for the creation of SNePSwD, present the form of default rules it uses, discuss the meaning of each of the three kinds of consequence, and describe how preferences can be specified among propositions and how these preferences are used in the process of belief revision. Finally we present examples that illustrate the aspects discussed in the paper.     

ORGANIZATIONAL MEMORY: THREE EXPERIMENTS ON THE QUALITY OF INFORMATION

Abstract

An expert system in ethical organizational administration is a new and appropriate venture for workers in artificial intelligence. The positive relationship between knowledge and belief along with the inextricable connection of fact to value set the general systems design for this modeling process. The premises of general systems theory dictate the modeling of an holistic ethical system. The pattern of the holistic ethical system of Orthodox Christianity is used to design the flow diagram of the decision-making and judgment-making processes in ethical thought. There are seven symbolic propositions that detail these ethical processes. With the public language of the United States being secular, four Orthodox Christian ethical principles were transformed from their biblical and theological language into four university ethical policies using secular language. The writer's future design of computer software will confirm or deny the wisdom of this approach to modeling an ethical system.     

A note on the approximation of Shenoy's expectation operator using probabilistic transforms

ABSTRACT

Recently, a new way of computing an expected value in the Dempster–Shafer theory of evidence was introduced by Prakash P. Shenoy. Up to now, when they needed the expected value of a utility function in D-S theory, the authors usually did it indirectly: first, they found a probability measure corresponding to the considered belief function, and then computed the classical probabilistic expectation using this probability measure. To the best of our knowledge, Shenoy's operator of expectation is the first approach that takes into account all the information included in the respective belief function. Its only drawback is its exponential computational complexity. This is why, in this paper, we compare five different approaches defining probabilistic representatives of belief function from the point of view, which of them yields the best approximations of Shenoy's expected values of utility functions.     

Uncertainty management in expert systems using fuzzy Petri nets

The paper aims at developing new techniques for uncertainty management in expert systems for two generic class of problems using fuzzy Petri nets that represent logical connectivity among a set of imprecise propositions. One class of problems deals with the computation of fuzzy belief of any proposition from the fuzzy beliefs of a set of independent initiating propositions in a given network. The other class of problems is concerned with the computation of steady-state fuzzy beliefs of the propositions embedded in the network, from their initial fuzzy beliefs through a process called belief revision. During belief revision, a fuzzy Petri net with cycles may exhibit “limit cycle behavior” of fuzzy beliefs for some propositions in the network. No decisions can be arrived at from a fuzzy Petri net with such behavior. To circumvent this problem, techniques have been developed for the detection and elimination of limit cycles. Further, an algorithm for selecting one evidence from each set of mutually inconsistent evidences, referred to as nonmonotonic reasoning, has also been presented in connection with the problems of belief revision. Finally, the concepts proposed for solving the problems of belief revision have been applied successfully for tackling imprecision, uncertainty, and nonmonotonicity of evidences in an illustrative expert system for criminal investigation     

A FRAMEWORK FOR LOGICS OF EXPLICIT BELIEF

The epistemic notions of knowledge and belief have most commonly been modeled by means of possible worlds semantics. In such approaches an agent knows (or believes) all logical consequences of its beliefs. Consequently, several approaches have been proposed to model systems of explicit belief, more suited to modeling finite agents or computers. In this paper a general framework is developed for the specification of logics of explicit belief. A generalization of possible worlds, called situations, is adopted. However the notion of an accessibility relation is not employed; instead a sentence is believed if the explicit proposition expressed by the sentence appears among a set of propositions associated with an agent at a situation. Since explicit propositions may be taken as corresponding to "belief contexts" or "frames of mind," the framework also provides a setting for investigating such approaches to belief. The approach provides a uniform and flexible basis from which various issues of explicit belief may be addressed and from which systems may be contrasted and compared. A family of logics is developed using this framework, which extends previous approaches and addresses issues raised by these earlier approaches. The more interesting of these logics are tractable, in that determining if a belief follows from a set of beliefs, given certain assumptions, can be accomplished in polynomial time.     

On Resolving Conflicts Between Arguments

Argument systems are based on the idea that one can construct arguments for propositions—structured reasons justifying the belief in a proposition. Using defeasible rules, arguments need not be valid in all circumstances, therefore, it might be possible to construct an argument for a proposition as well as its negation. When arguments support conflicting propositions, one of the arguments must be defeated, which raises the question of which (sub‐) arguments can be subject to defeat. In legal argumentation, metarules determine the valid arguments by considering the last defeasible rule of each argument involved in a conflict. Since it is easier to evaluate arguments using their last rules, can a conflict be resolved by considering only the last defeasible rules of the arguments involved? We propose a new argument system where, instead of deriving a defeat relation between arguments, arguments for the defeat of defeasible rules are constructed. This system allows us to determine a set of valid (undefeated) arguments in linear time using an algorithm based on a JTMS, allows conflicts to be resolved using only the last rules of the arguments, allows us to establish a relation with Default Logic, and allows closure properties such as cumulativity to be proved. We propose an extension of the argument system based on a proposal for reasoning by cases in default logic.     

The Strength of Desires: A Logical Approach

The aim of this paper is to propose a formal approach to reasoning about desires, understood as logical propositions which we would be pleased to make true, also acknowledging the fact that desire is a matter of degree. It is first shown that, at the static level, desires should satisfy certain principles that differ from those to which beliefs obey. In this sense, from a static perspective, the logic of desires is different from the logic of beliefs. While the accumulation of beliefs tend to reduce the remaining possible worlds they point at, the accumulation of desires tends to increase the set of states of affairs tentatively considered as satisfactory. Indeed beliefs are expected to be closed under conjunctions, while, in the positive view of desires developed here, one can argue that endorsing \(\varphi \vee \psi\) as a desire means to desire \(\varphi\) and to desire \(\psi\). However, desiring \(\varphi\) and \(\lnot \varphi\) at the same time is not usually regarded as rational, since it does not make much sense to desire one thing and its contrary at the same time. Thus when a new desire is added to the set of desires of an agent, a revision process may be necessary. Just as belief revision relies on an epistemic entrenchment relation, desire revision is based on a hedonic entrenchment relation satisfying other properties, due to the different natures of belief and desire. While epistemic entrenchment relations are known to be qualitative necessity relations (in the sense of possibility theory), hedonic relations obeying a set of reasonable postulates correspond to another set-function in possibility theory, called guaranteed possibility, that drive well-behaved desire revision operations. Then the general framework of possibilistic logic provides a syntactic setting for encoding desire change. The paper also insists that desires should be carefully distinguished from goals.     

A conditional logic for defeasible beliefs

This paper provides a framework for representing beliefs by distinguishing between (i) the defeasible principles of a belief system, (ii) the propositions that are beyond reasonable doubt in a belief state, and (iii) the propositions ‘favored’ on the basis of defeasible principles and those propositions that are beyond reasonable doubt. Defeasible principles are interpreted semantically by means of a Lewis-style ranking of worlds (without the assumption that the actual world is among the ‘innermost’, or most highly ranked, worlds). The ‘favored closure’ (F-closure) of a set of defeasible principles and reasonable propositions is non-monotonic. Yet, given the concept of ‘pruning’ the default ranking relative to a set of worlds (determined by what is beyond reasonable doubt in a particular belief state) we provide a formal characterization of the conditions under which in inference to a favored conclusion on the basis of defeasible rules and reasonable propositions, is warranted. The adequacy of our representation of defeasible principles can be tested by considering a number of valid formulas that we list. We show that our concept of defeasible principle parallels but is not identical to the concept of ‘relatively high conditional probability’. An example of application of the formal language and semantics is given, and the final parts of the paper contain u     

The animate – inanimate relationship

This paper defends two beliefs denied by many scientists. The first is a belief in an alternative hypothesis to that of the prevailing view of life’s origin from existing inanimate matter. In defence of the need for an alternative we call attention to evidence that precludes the prevailing view. Our second defended belief is for the existence of a life force. In its defence, we cite what is known physiology concerning catabolic and anabolic aspects of metabolism.     

Mutual Misunderstanding: Preservice Science Teachers’ and Instructors’ Mismatching(?) Priorities

Abstract

There is a growing movement to incorporate and integrate ethics and socioscientific issues (SSIs) into the school science curriculum. Educating prospective science teachers about the importance of SSI is an important aspect of this movement. One area of particular interest is the role of participant beliefs about SSI in shaping the content of teacher education courses, particularly in the physical sciences. This study compared the beliefs of teacher candidates with the beliefs of their instructors on the topic of injecting ethics and SSI into teaching the physical sciences. Findings indicate that teacher candidates have progressive views about teaching ethics and SSI. However, instructor practices are based on a belief that their students hold the opposite view. The result is a mismatching of student and instructor priorities and ambiguity around the teaching of science and ethics.     

Stability and Scepticism in the Modelling of Doxastic States: Probabilities and Plain Beliefs

There are two prominent ways of formally modelling human belief. One is in terms of plain beliefs (yes-or-no beliefs, beliefs simpliciter), i.e., sets of propositions. The second one is in terms of degrees of beliefs, which are commonly taken to be representable by subjective probability functions. In relating these two ways of modelling human belief, the most natural idea is a thesis frequently attributed to John Locke: a proposition is or ought to be believed (accepted) just in case its subjective probability exceeds a contextually fixed probability threshold \(t<1\). This idea is known to have two serious drawbacks: first, it denies that beliefs are closed under conjunction, and second, it may easily lead to sets of beliefs that are logically inconsistent. In this paper I present two recent accounts of aligning plain belief with subjective probability: the Stability Theory of Leitgeb (Ann Pure Appl Log 164(12):1338–1389, 2013; Philos Rev 123(2):131–171, 2014; Proc Aristot Soc Suppl Vol 89(1):143–185, 2015a; The stability of belief: an essay on rationality and coherence. Oxford University Press, Oxford, 2015b) and the Probalogical Theory (or Tracking Theory) of Lin and Kelly (Synthese 186(2):531–575, 2012a; J Philos Log 41(6):957–981, 2012b). I argue that Leitgeb’s theory may be too sceptical for the purposes of real life.     

A review of: “ANTICIPATORY SYSTEMS”, by Robert Rosen,Pergamon Press,Oxford, 1985, X + 436pp.

In rough set theory there exists a pair of approximation operators, the upper and lower approximations, whereas in Dempster-Shafer theory of evidence there exists a dual pair of uncertainty measures, the plausibility and belief functions. It seems that there is some kind of natural connection between the two theories. The purpose of this paper is to establish the relationship between rough set theory and Dempster-Shafer theory of evidence. Various generalizations of the Dempster-Shafer belief structure and their induced uncertainty measures, the plausibility and belief functions, are first reviewed and examined. Generalizations of Pawlak approximation space and their induced approximation operators, the upper and lower approximations, are then summarized. Concepts of random rough sets, which include the mechanisms of numeric and non-numeric aspects of uncertain knowledge, are then proposed. Notions of the Dempster-Shafer theory of evidence within the framework of rough set theory are subsequently formed and interpreted. It is demonstrated that various belief structures are associated with various rough approximation spaces such that different dual pairs of upper and lower approximation operators induced by the rough approximation spaces may be used to interpret the corresponding dual pairs of plausibility and belief functions induced by the belief structures.     

A qualitative discriminant approach for generating quantitativebelief functions

The authors present an approach that will be useful in knowledge acquisition from experts on the degree of belief in, or the probability of, the truthfulness of various propositions. Its advantages include exploring the given problem situation using linguistic quantifiers; avoiding the premature use of numeric measures; and identifying input data that is inconsistent with the theory of belief functions     

Reasons for bottlenecks in very large-scale system of systems development

ContextSystem of systems (SoS) is a set or arrangement of systems that results when independent and useful systems are to be incorporated into a larger system that delivers unique capabilities. Our investigation showed that the development life cycle (i.e. the activities transforming requirements into design, code, test cases, and releases) in SoS is more prone to bottlenecks in comparison to single systems.ObjectiveThe objective of the research is to identify reasons for bottlenecks in SoS, prioritize their significance according to their effect on bottlenecks, and compare them with respect to different roles and different perspectives, i.e. SoS view (concerned with integration of systems), and systems view (concerned with system development and delivery).MethodThe research method used is a case study at Ericsson AB.ResultsResults show that the most significant reasons for bottlenecks are related to requirements engineering. All the different roles agree on the significance of requirements related factors. However, there are also disagreements between the roles, in particular with respect to quality related reasons. Quality related hinders are primarily observed and highly prioritized by quality assurance responsibles. Furthermore, SoS view and system view perceive different hinders, and prioritize them differently.ConclusionWe conclude that solutions for requirements engineering in SoS context are needed, quality awareness in the organization has to be achieved end to end, and views between SoS and system view need to be aligned to avoid sub optimization in improvements.     

Model-based testing of global properties on large-scale distributed systems

ContextLarge-scale distributed systems are becoming commonplace with the large popularity of peer-to-peer and cloud computing. The increasing importance of these systems contrasts with the lack of integrated solutions to build trustworthy software. A key concern of any large-scale distributed system is the validation of global properties, which cannot be evaluated on a single node. Thus, it is necessary to gather data from distributed nodes and to aggregate these data into a global view. This turns out to be very challenging because of the system’s dynamism that imposes very frequent changes in local values that affect global properties. This implies that the global view has to be frequently updated to ensure an accurate validation of global properties.ObjectiveIn this paper, we present a model-based approach to define a dynamic oracle for checking global properties. Our objective is to abstract relevant aspects of such systems into models. These models are updated at runtime, by monitoring the corresponding distributed system.MethodWe conduce real-scale experimental validation to evaluate the ability of our approach to check global properties. In this validation, we apply our approach to test two open-source implementations of distributed hash tables. The experiments are deployed on two clusters of 32 nodes.ResultsThe experiments reveal an important defect on one implementation and show clear performance differences between the two implementations. The defect would not be detected without a global view of the system.ConclusionTesting global properties on distributed software consists of gathering data from different nodes and building a global view of the system, where properties are validated. This process requires a distributed test architecture and tools for representing and validating global properties. Model-based techniques are an expressive mean for building oracles that validate global properties on distributed systems.     

Investigating Architectural Technical Debt accumulation and refactoring over time: A multiple-case study

ContextA known problem in large software companies is to balance the prioritization of short-term with long-term feature delivery speed. Specifically, Architecture Technical Debt is regarded as sub-optimal architectural solutions taken to deliver fast that might hinder future feature development, which, in turn, would hinder agility.ObjectiveThis paper aims at improving software management by shedding light on the current factors responsible for the accumulation of Architectural Technical Debt and to understand how it evolves over time.MethodWe conducted an exploratory multiple-case embedded case study in 7 sites at 5 large companies. We evaluated the results with additional cross-company interviews and an in-depth, company-specific case study in which we initially evaluate factors and models.ResultsWe compiled a taxonomy of the factors and their influence in the accumulation of Architectural Technical Debt, and we provide two qualitative models of how the debt is accumulated and refactored over time in the studied companies. We also list a set of exploratory propositions on possible refactoring strategies that can be useful as insights for practitioners and as hypotheses for further research.ConclusionSeveral factors cause constant and unavoidable accumulation of Architecture Technical Debt, which leads to development crises. Refactorings are often overlooked in prioritization and they are often triggered by development crises, in a reactive fashion. Some of the factors are manageable, while others are external to the companies. ATD needs to be made visible, in order to postpone the crises according to the strategic goals of the companies. There is a need for practices and automated tools to proactively manage ATD.     

Modelling linear fractional transportation problem in belief degree—based uncertain environment

A linear fractional transportation problem in uncertain environment is studied in this paper where the uncertain parameters of the problem are of belief degree—based uncertainty. For the first time, this type of uncertainty is considered for the linear fractional transportation problem. Belief degree—based uncertainty is useful for the cases that no historical information of an uncertain event is available. Zigzag type uncertainty distribution is used to show the belief degree—based uncertainty of the parameters of the problem. As solution methodology, the uncertain linear fractional transportation problem is converted to a crisp form using three approaches of expected value model, expected value and chance-constrained model, and chance-constrained model, separately. An extensive computational study on a real illustrative example shows the efficiency of the proposed formulation and the conversion approaches. The sensitivity analysis over the example illustrates the high dependency of the objective function value to the changes of the confidence level values of the chance constraints in the expected value and chance-constrained programming approach and the chance-constrained programming approach.