Answer Set Programming based on Propositional Satisfiability

Answer set programming (ASP) emerged in the late 1990s as a new logic programming paradigm that has been successfully applied in various application domains. Also motivated by the availability of efficient solvers for propositional satisfiability (SAT), various reductions from logic programs to SAT were introduced. All these reductions, however, are limited to a subclass of logic programs or introduce new variables or may produce exponentially bigger propositional formulas. In this paper, we present a SAT-based procedure, called ASPSAT, that (1) deals with any (nondisjunctive) logic program, (2) works on a propositional formula without additional variables (except for those possibly introduced by the clause form transformation), and (3) is guaranteed to work in polynomial space. From a theoretical perspective, we prove soundness and completeness of ASPSAT. From a practical perspective, we have (1) implemented ASPSAT in Cmodels, (2) extended the basic procedures in order to incorporate the most popular SAT reasoning strategies, and (3) conducted an extensive comparative analysis involving other state-of-the-art answer set solvers. The experimental analysis shows that our solver is competitive with the other solvers we considered and that the reasoning strategies that work best on ‘small but hard’ problems are ineffective on ‘big but easy’ problems and vice versa

Anxiety Sensitivity : Validity of the Anxiety Sensitivity Profile on a Clinical Sample

The psychometric properties of the Anxiety Sensitivity Index (ASI) have been criticized. Although it has been the gold standard in research and assessment, its reliability (i.e., internal consistency) has been questioned. There are doubts about its ability to identify accurately the underlying factors for anxiety sensitivity. To provide a more accurate description of the anxiety sensitivity construct, Taylor and Cox (1998) developed the Anxiety Sensitivity Profile (ASP) and performed analyses based on a sample of 349 university students. The current study utilized a clinical sample to test the hypotheses that the ASP would have convergent validity with the ASI and discriminant validity with the trait version of the State-Trait Anxiety Inventory (STAl). This correlational study was conducted with a clinical sample of 105 adults, 19 to 65 years old, who have an anxiety disorder. Each subject completed the ASP, ASI, STAl, and the computerized version of the SClD-I/P. Results supported the hypotheses. Large correlations at the .01 level were found for the ASP and ASI total scores and ASP subscale scores. Modest correlations were found for the ASI and ASP total and subscale scores and the trait version of the STAl at the .05 level. Reliability (internal consistency) for the ASI total scores and ASP subscales was high. Therefore this study provides evidence for convergent validity with the ASI. It also provides necessary, although not sufficient evidence for construct validity for the ASP subscales. Internal consistency reliability cannot be determined for all of the underlying domains of the ASI, because one of the domains consists of only one item. This evidence implies that the ASP is psychometrically superior to the ASI for research and treatment. Instead of the three underlying factors of the ASI, six factors are implied. Evidence is provided through convergent validity and internal consistency reliability found for the six ASP subscales. It is speculated that utilization of the ASP will support improved consistency in research through the use of congruence (i.e., matching the symptoms caused by a provocation task and the symptoms a person fears). Furthermore the ASP will support accurate identification of the domains underlying anxiety sensitivity that contribute to its association with all anxiety disorders. Finally, there are applied implications. These include the fact that those at risk can be identified and given brief cognitive-behavioral therapy as a preventive intervention. Also, treatment can target congruent cognitions, and elevated anxiety sensitivity at the end of treatment can be targeted for further interventions

The emergence of active perception - seeking conceptual foundations

The aim of this thesis is to explain the emergence of active perception. It takes an interdisciplinary approach, by providing the necessary conceptual foundations for active perception research - the key notions that bridge the conceptual gaps remaining in understanding emergent behaviours of active perception in the context of robotic implementations. On the one hand, the autonomous agent approach to mobile robotics claims that perception is active. On the other hand, while explanations of emergence have been extensively pursued in Artificial Life, these explanations have not yet successfully accounted for active perception.The main question dealt with in this thesis is how active perception systems, as behaviour -based autonomous systems, are capable of providing relatively optimal perceptual guidance in response to environmental challenges, which are somewhat unpredictable. The answer is: task -level emergence on grounds of complicatedly combined computational strategies, but this notion needs further explanation.To study the computational strategies undertaken in active perception re- search, the thesis surveys twelve implementations. On the basis of the surveyed implementations, discussions in this thesis show that the perceptual task executed in support of bodily actions does not arise from the intentionality of a homuncu- lus, but is identified automatically on the basis of the dynamic small mod- ules of particular robotic architectures. The identified tasks are accomplished by quasi -functional modules and quasi- action modules, which maintain transformations of perceptual inputs, compute critical variables, and provide guidance of sensory -motor movements to the most relevant positions for fetching further needed information. Given the nature of these modules, active perception emerges in a different fashion from the global behaviour seen in other autonomous agent research.The quasi- functional modules and quasi- action modules cooperate by estimating the internal cohesion of various sources of information in support of the envisaged task. Specifically, such modules basically reflect various computational facilities for a species to single out the most important characteristics of its ecological niche. These facilities help to achieve internal cohesion, by maintaining a stepwise evaluation over the previously computed information, the required task, and the most relevant features presented in the environment.Apart from the above exposition of active perception, the process of task - level emergence is understood with certain principles extracted from four models of life origin. First, the fundamental structure of active perception is identified as the stepwise computation. Second, stepwise computation is promoted from baseline to elaborate patterns, i.e. from a simple system to a combinatory system. Third, a core requirement for all stepwise computational processes is the comparison between collected and needed information in order to insure the contribution to the required task. Interestingly, this point indicates that active perception has an inherent pragmatist dimension.The understanding of emergence in the present thesis goes beyond the distinc- tion between external processes and internal representations, which some current philosophers argue is required to explain emergence. The additional factors are links of various knowledge sources, in which the role of conceptual foundations is two -fold. On the one hand, those conceptual foundations elucidate how various knowledge sources can be linked. On the other, they make possible an interdisci- plinary view of emergence. Given this two -fold role, this thesis shows the unity of task -level emergence. Thus, the thesis demonstrates a cooperation between sci- ence and philosophy for the purpose of understanding the integrity of emergent cognitive phenomena

An Aesthetics of Hauntology

The text sets out to consider the aspects of the spectral, as proposed by Derrida in Spectres of Marx. As an alteric revenant refuting the historical/chronological determination of ratio and universality, it haunts the architectonics of the metaphysical edifice. This spectral 'operation' is also an activity of encryption which involves a discussion speculating on the virtual by proposing the transgressive rift as an introjective interruption that is realised through the abysmal (dis)order of fenestration. It uncovers a thematic of topological (dis)location via a series of 'meridial threads' which the dissertation seeks to explore through a scrutiny of aesthetics and specific creative activities. The first chapter explores this 'relation' with specific attention given to the alteric rift as an operation of differance as indicated by Derrida and seeks to critique this juxtaposition with particular reference and attention to Kant's aesthetics. Chapter two identifies Paul Celan's poem 'Todtnauberg' as a topos for a discussion on anticipation and silence in the complex historical relationship between the poet and the philosopher Martin Heidegger, as 'reported' in the poem. It identifies the topology of 'meridial haunting' at Heidegger's Black Forest mountain retreat. 'The Unheimlich Manoeuvre' (chapter three) deals with two key works by the architectural interventionist Gordon Matta-Clark, through a discussion on the uncanny (Unheimlich) and its relation to the homely (Heimlich), taking into account the encystic operation of mourning. The Final chapter continues this theme of the architecturally 'interruptive' by considering orientation with specific attention to the labyrinthine and the temporality of the crystal-image as cited by Deleuze in his writings on cinema and the spectral. It looks specifically at two films by Tarkovsky; Solaris and Stalker and Mark Z. Danelewski's novel House of Leaves (a complex fictitious account of a nonexistent documentary film which recounts the exploration of a labyrinth which appears in an ordinary suburban house)