532 research outputs found

    Consistent Query Answering for Primary Keys on Rooted Tree Queries

    Full text link
    We study the data complexity of consistent query answering (CQA) on databases that may violate the primary key constraints. A repair is a maximal subset of the database satisfying the primary key constraints. For a Boolean query q, the problem CERTAINTY(q) takes a database as input, and asks whether or not each repair satisfies q. The computational complexity of CERTAINTY(q) has been established whenever q is a self-join-free Boolean conjunctive query, or a (not necessarily self-join-free) Boolean path query. In this paper, we take one more step towards a general classification for all Boolean conjunctive queries by considering the class of rooted tree queries. In particular, we show that for every rooted tree query q, CERTAINTY(q) is in FO, NL-hard \cap LFP, or coNP-complete, and it is decidable (in polynomial time), given q, which of the three cases applies. We also extend our classification to larger classes of queries with simple primary keys. Our classification criteria rely on query homomorphisms and our polynomial-time fixpoint algorithm is based on a novel use of context-free grammar (CFG).Comment: To appear in PODS'2

    Jews in East Norse Literature

    Get PDF
    This book explores the portrayal of Jews and Judaism in medieval Danish and Swedish literary and visual culture. Drawing on over 100 manuscripts and incunabula as well as runic inscriptions and religious art, the author describes the various, often contradictory, images ranging from antisemitism and anti-Judaism to the elevation of Jews as morally exemplary figures. It includes new editions of 54 East Norse texts with English translations

    LIPIcs, Volume 261, ICALP 2023, Complete Volume

    Get PDF
    LIPIcs, Volume 261, ICALP 2023, Complete Volum

    Enduring Displacement, Enduring Violence: Camps, Closure, and Exile In/After Return (Experiences of Burundian Refugees in Tanzania)

    Get PDF
    “Return home” was the joint message by the Burundian and Tanzanian presidents in 2017, just two years after hundreds of thousands Burundians were recognized as refugees in neighbouring countries, and as more continued to seek refuge or asylum each month. In Tanzania, where refugees are subject to strict encampment, the vast majority of Burundian refugees had previously been refugees at least once before. Many returned to Tanzania less than three years after their prior return to Burundi, which, as camps were closed, had been framed as a “durable solution” to their displacement. This thesis explores the interrelated dynamics of enduring displacement, encampment, and closure, by drawing on life history research with Burundian refugees in two camps in Tanzania (2017-8), as well as semi-structured interviews with government and humanitarian staff, and ethnographic methods. Empirically, this dissertation contributes to knowledge by tracing the diverse prior trajectories of current Burundian refugees, both within and beyond camp boundaries, challenging there-and-back-again geographical imaginary of refuge management. It highlights an understudied but constitutive aspect of camps—their ultimate closures—by recounting refugees’ memories of the violent closure of Mtabila camp, as well as its fearful afterlives and present-presence. The violence of past camp closure is part of the violence of current encampment due to its evocation as a a disciplinary dispositif to “encourage” return, threatening and anticipating future violence. State and humanitarian practices “close” and harden space for those deemed “undesirable,” through forced encampment, camp closures, and coerced or forced return. In so doing, they produce and prolong displacement, in which varied spatio-temporalities of violence endure. Burundian refugees’ life histories thus trace the ways displacement endures, and is endured

    Covid Conspiracy Theories in Global Perspective

    Get PDF
    Covid Conspiracy Theories in Global Perspective examines how conspiracy theories and related forms of misinformation and disinformation about the Covid-19 pandemic have circulated widely around the world. Covid conspiracy theories have attracted considerable attention from researchers, journalists, and politicians, not least because conspiracy beliefs have the potential to negatively affect adherence to public health measures. While most of this focus has been on the United States and Western Europe, this collection provides a unique global perspective on the emergence and development of conspiracy theories through a series of case studies. The chapters have been commissioned by recognized experts on area studies and conspiracy theories. The chapters present case studies on how Covid conspiracism has played out (some focused on a single country, others on regions), using a range of methods from a variety of disciplinary perspectives, including history, politics, sociology, anthropology, and psychology. Collectively, the authors reveal that, although there are many narratives that have spread virally, they have been adapted for different uses and take on different meanings in local contexts. This volume makes an important contribution to the rapidly expanding field of academic conspiracy theory studies, as well as being of interest to those working in the media, regulatory agencies, and civil society organizations, who seek to better understand the problem of how and why conspiracy theories spread

    Operational research:methods and applications

    Get PDF
    Throughout its history, Operational Research has evolved to include a variety of methods, models and algorithms that have been applied to a diverse and wide range of contexts. This encyclopedic article consists of two main sections: methods and applications. The first aims to summarise the up-to-date knowledge and provide an overview of the state-of-the-art methods and key developments in the various subdomains of the field. The second offers a wide-ranging list of areas where Operational Research has been applied. The article is meant to be read in a nonlinear fashion. It should be used as a point of reference or first-port-of-call for a diverse pool of readers: academics, researchers, students, and practitioners. The entries within the methods and applications sections are presented in alphabetical order

    LIPIcs, Volume 274, ESA 2023, Complete Volume

    Get PDF
    LIPIcs, Volume 274, ESA 2023, Complete Volum

    Rules Britannia: Board Games, Britain, and the World, c. 1759-1860

    Get PDF
    Focusing on Georgian and Victorian Britain, this thesis examines didactic boardgames as cultural artefacts exploring the bounds of moral sympathy and responsibility in an ostensibly Anglocentric world. It refutes previous conclusions that exposure to imperial ideology via these games in childhood necessarily led to an imperialist identity in adulthood and thence to imperialist activity later in the nineteenth century, highlighting instead how games encouraged players to question the appropriateness of affiliating oneself with the British imperial project by accounting for circumstantial differences at home and abroad. It defies a hypodermic model of communication which posits players as passive and highly susceptible to manipulation by demonstrating instances of player modifications to rules and/or content that, in changing the values and assumptions of the original game, suggest what contemporaries found to be objectionable or missing in standard gameplay. It examines this dialectic between game and player across four thematic categories: teleological games, geographical games, ethnographic games, and zoological games

    Operational Research: Methods and Applications

    Get PDF
    Throughout its history, Operational Research has evolved to include a variety of methods, models and algorithms that have been applied to a diverse and wide range of contexts. This encyclopedic article consists of two main sections: methods and applications. The first aims to summarise the up-to-date knowledge and provide an overview of the state-of-the-art methods and key developments in the various subdomains of the field. The second offers a wide-ranging list of areas where Operational Research has been applied. The article is meant to be read in a nonlinear fashion. It should be used as a point of reference or first-port-of-call for a diverse pool of readers: academics, researchers, students, and practitioners. The entries within the methods and applications sections are presented in alphabetical order. The authors dedicate this paper to the 2023 Turkey/Syria earthquake victims. We sincerely hope that advances in OR will play a role towards minimising the pain and suffering caused by this and future catastrophes

    A review of commercialisation mechanisms for carbon dioxide removal

    Get PDF
    The deployment of carbon dioxide removal (CDR) needs to be scaled up to achieve net zero emission pledges. In this paper we survey the policy mechanisms currently in place globally to incentivise CDR, together with an estimate of what different mechanisms are paying per tonne of CDR, and how those costs are currently distributed. Incentive structures are grouped into three structures, market-based, public procurement, and fiscal mechanisms. We find the majority of mechanisms currently in operation are underresourced and pay too little to enable a portfolio of CDR that could support achievement of net zero. The majority of mechanisms are concentrated in market-based and fiscal structures, specifically carbon markets and subsidies. While not primarily motivated by CDR, mechanisms tend to support established afforestation and soil carbon sequestration methods. Mechanisms for geological CDR remain largely underdeveloped relative to the requirements of modelled net zero scenarios. Commercialisation pathways for CDR require suitable policies and markets throughout the projects development cycle. Discussion and investment in CDR has tended to focus on technology development. Our findings suggest that an equal or greater emphasis on policy innovation may be required if future requirements for CDR are to be met. This study can further support research and policy on the identification of incentive gaps and realistic potential for CDR globally
    corecore