8,397 research outputs found
A tetrachotomy of ontology-mediated queries with a covering axiom
Our concern is the problem of efficiently determining the data complexity of answering queries mediated by descrip- tion logic ontologies and constructing their optimal rewritings to standard database queries. Originated in ontology- based data access and datalog optimisation, this problem is known to be computationally very complex in general, with no explicit syntactic characterisations available. In this article, aiming to understand the fundamental roots of this difficulty, we strip the problem to the bare bones and focus on Boolean conjunctive queries mediated by a simple cov- ering axiom stating that one class is covered by the union of two other classes. We show that, on the one hand, these rudimentary ontology-mediated queries, called disjunctive sirups (or d-sirups), capture many features and difficulties of the general case. For example, answering d-sirups is Î 2p-complete for combined complexity and can be in AC0 or L-, NL-, P-, or coNP-complete for data complexity (with the problem of recognising FO-rewritability of d-sirups be- ing 2ExpTime-hard); some d-sirups only have exponential-size resolution proofs, some only double-exponential-size positive existential FO-rewritings and single-exponential-size nonrecursive datalog rewritings. On the other hand, we prove a few partial sufficient and necessary conditions of FO- and (symmetric/linear-) datalog rewritability of d- sirups. Our main technical result is a complete and transparent syntactic AC0 / NL / P / coNP tetrachotomy of d-sirups with disjoint covering classes and a path-shaped Boolean conjunctive query. To obtain this tetrachotomy, we develop new techniques for establishing P- and coNP-hardness of answering non-Horn ontology-mediated queries as well as showing that they can be answered in NL
Demand fulfillment in customer hierarchies with stochastic demand
Supply scarcity, due to demand or supply fluctuations, is a common issue in make-to-stock production systems. To increase profits when customers are heterogeneous, firms need to decide whether to accept a customer order or reject it in anticipation of more profitable orders, and if accepted, which supplies to use in order to fulfill the order. Such issues are addressed by solving demand fulfillment problems. In order to provide a solution, firms commonly divide their customers into different segments, based on their respective profitability. The available supply is first allocated to the customer segments based on their projected demand information. Then, as customer orders materialize, the allocated quotas are consumed. The customer segments commonly have a multilevel hierarchical structure, which reflects the structure of the sales organization. In this thesis, we study the demand fulfillment problem in make-to-stock production systems, considering such customer hierarchies with stochastic demand.
In the hierarchical setting, the available supply is allocated level by level from top to bottom of the hierarchy by multiple planners on different levels. The planners on higher levels of the hierarchy need to make their allocation decisions based on aggregated information, since transmitting all detailed demand information from the bottom to the top of the hierarchy is not generally feasible. In practice, simplistic rules of thumb are applied to deal with this decentralized problem, which lead to sub-optimal results. We aim to provide more effective approaches that result in near-optimal solutions to this decentralized problem.
We first consider the single-period problem with a single supply replenishment and focus on identifying critical information for good, decentralized allocation decisions. We propose two decentralized allocation methods, namely a stochastic Theil index approximation and a clustering approach, which provide near-optimal results even for large, complicated hierarchies. Both methods transmit aggregated information about profit heterogeneity and demand uncertainty in the hierarchy, which is missing in the current simplistic rules.
Subsequently, we expand our analysis to a multi-period setting, in which periodic supply replenishments are considered and periods are interconnected by inventory or backlog. We consider a periodic setting, meaning that in each period we allow multiple orders from multiple customer segments. We first formalize the centralized problem as a two-stage stochastic dynamic program. Due to the curse of dimensionality, the problem is computationally intractable. Therefore, we propose an approximate dynamic programming heuristic. For the decentralized case, we consider our proposed clustering method and modify it to fit the multi-period setting, relying on the approximate dynamic programming heuristic. Our results show that the proposed heuristics lead to profits very close to the ex-post optimal solution for both centralized and decentralized problems.
Finally, we look into the order promising stage and compare different consumption functions, namely partitioned, rule-based nested, and bid price methods. Our results show that nesting leads to performance improvements compared to partitioned consumption.
However, for decentralized problems, the improvement resulting from nesting cannot mitigate the profit loss from considerable mis-allocations made by simplistic rules, except for cases with high demand uncertainty or low profit heterogeneity. Moreover, among the nested consumption functions, the bid price approach, which integrates the allocation and consumption stages, leads to a higher performance than the rule-based consumption methods.
Altogether, our proposed decentralized methods lead to drastic profit improvements compared to the current simplistic rules for demand fulfillment in customer hierarchies, except for cases with very low shortage or for largely homogeneous customers, where simplistic rules perform similarly well. Applying our advanced methods is especially important when the shortage rate is high or customers are more heterogeneous. Regarding order promising, nesting is more crucial when demand uncertainty is high.
The research presented in this thesis was undertaken as part of the project âdemand fulfillment in customer hierarchiesâ. It was funded by the German Research Foundation (DFG) under grant FL738/2-1
Post-Millennial Queer Sensibility: Collaborative Authorship as Disidentification in Queer Intertextual Commodities
This dissertation is examining LGBTQ+ audiences and creatives collaborating in the creation of new media texts like web shows, podcasts, and video games. The study focuses on three main objects or media texts: Carmilla (web series), Welcome to Night Vale (podcast), and Undertale (video game). These texts are transmedia objects or intertextual commodities. I argue that by using queer gestures of collaborative authorship that reaches out to the audience for canonical contribution create an emerging queer production culture that disidentifies with capitalism even as it negotiates capitalistic structures. The post-millennial queer sensibility is a constellation of aesthetics, self-representation, alternative financing, and interactivity that prioritizes community, trust, and authenticity using new technologies for co-creation.
Within my study, there are four key tactics or queer gestures being explored: remediation, radical ambiguity and multi-forms as queer aesthetics, audience self-representation, alternative financing like micropatronage & licensed fan-made merchandise, and interactivity as performance. The goal of this project is to better understand the changing conceptions of authorship/ownership, canon/fanon (official text/fan created extensions), and community/capitalism in queer subcultures as an indicator of the potential change in more mainstream cultural attitudes. The project takes into consideration a variety of intersecting identities including gender, race, class, and of course sexual orientation in its analysis. By examining the legal discourse around collaborative authorship, the real-life production practices, and audience-creator interactions and attitudes, this study provides insight into how media creatives work with audiences to co-create self-representative media, the motivations, and rewards for creative, audiences, and owners. This study aims to contribute towards a fuller understanding of queer production cultures and audience reception of these media texts, of which there is relatively little academic information. Specifically, the study mines for insights into the changing attitudes towards authorship, ownership, and collaboration within queer indie media projects, especially as these objects are relying on the self-representation of both audiences and creatives in the formation of the text
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After Creation: Intergovernmental Organizations and Member State Governments as Co-Participants in an Authority Relationship
This is a re-amalgamation of what started as one manuscript and became two when the length proved to be more than any publisher wanted to consider. The splitting consisted of removing what are now Parts 3, 4, and 5 so that the manuscript focused on the outcome-related shared beliefs holding an authority relationship together. Those parts were last worked on in 2018. The rest were last worked on in late 2021 but also remain incomplete.
The relational approach adopted in this study treats intergovernmental organizations and the governments of member states as co-participants in an authority relationship with the governments of their member states. Authority relationships link two types of actor, defined by their authority-holder or addressee role in the relationship, through a set of shared beliefs about why the relationship exists and how the participants should fulfill their respective roles. The IGO as authority holder has a role that includes a right to instruct other actors about what they should or should not do; the governments of member states as addressees are expected to comply with the instructions. Three sets of shared beliefs provide the conceptual âglueâ holding the relationship together. The first defines the goal of the collective effort, providing both the rationale for having the authority relationship and providing a lode star for assessments of the collective effortâs success or lack of success. The second set defines the shared understanding about allocation of roles and the process of interaction by establishing shared expectations about a) the selection process by which particular actors acquire authority holder roles, b) the definitions identifying one or more categories of addressees expected to follow instructions, and c) the procedures through which the authority holder issues instructions. The third set focus on the outcomes of cooperation through the relationship by defining a) the substantive areas in which the authority holder may issue instructions, b) the bases for assessing the relevance actions mandated in instructions for reaching the goal, and c) the relative efficacy of action paths chosen for reaching the goal as compared to other possible action paths.
Using an authority relationship framework for analyzing cooperation through IGOs highlights the inherently bi-directional nature of IGO-member government activity by viewing their interaction as involving a three-step process in which the IGO as authority holder decides when to issue what instruction, the member state governments as followers react to the instruction with anything from prompt and full compliance through various forms of pushback to outright rejection, and the IGO as authority holder responds to how the followers react with efforts to increase individual compliance with instructions and reinforce continuing acceptance of the authority relationship. Foregrounding the dynamics produced by the interaction of these two streams of perception and action reveals more clearly how far intergovernmental organizations acquire capacity to operate as independent actors, the dynamic ways they maintain that capacity, and how much they influence member governmentsâ beliefs and actions at different times. The approach fosters better understanding of why, when, and for how long governments choose cooperation through an IGO even in periods of rising unilateralism
Management Matters : Organizational Storytelling within the Anthroposophical Society in Sweden
The Anthroposophical Society, founded by the Austrian polymath Rudolf Steiner, came to Sweden in 1913, but for the generation of present-day Swedish Anthroposophists whose voices are heard in this study, the great flowering of the movement occurred in the second half of the twentieth century. The movement had by then expanded into a large milieu with many largely independent enterprises and institutions, from the formal organization itself, to various schools, farms, shops, medical facilities, etc., all based on interpretations of Steinerâs legacy. Since then, many members of the movement feel, there has been a decline.
A movement of this size and complexity can be seen as a large organization with a corporate-like structure. Taking its point of departure in ideas from the vast field of organization studies, and specifically in the study of storytelling as part of the creation of a corporate culture where many voices and many perspectives co-exist, this study investigates how Anthroposophists in Sweden, both rank and-file members and some who served in leadership positions, tell the story of the putative Golden Age, decline, and projected future of Anthroposophy in Sweden. Twenty-eight interviews were collected, recurrent themes identified, and the plots of the various individual stories analyzed by means of a version of the actantial model developed by the semioticist Algirdas Greimas.
The basic storyline, of which the intervieweesâ individual stories constitute variations, is that the Golden Age, when charismatic leaders could draw crowds of enthusiastic young people and a vibrant Anthroposophical milieu was built up, came to an end with the demise of those leaders. The present, i.e., the time at which the interviews were conducted, is narratively framed as a period of sharp decline. The vistas for the future come across in most stories as quite bleak. An actantial analysis reveals that the past, an epoch that is on one hand held up as a shining example is on the other hand also described as a time characterized by innumerable problems and conflicts. Disagreement is rampant regarding the reasons for the current decline, and a vast number of problems are identified in the individual narratives. The future is for some interviewees impossible to speculate about, whereas others have specific suggestions for change. These suggestions, when held up against each other, show that there is no unified vision of what the necessary changes might be or who must bring them about.
The interviewees agree that Anthroposophy plays a vital role as a spiritual path. When asked how they would describe Anthroposophy and what it more specifically can offer, answers diverge, but substantive descriptions of core concepts or practices are rarely alluded to. Rather, their explanations of what Anthroposophy is are in almost all cases metaphorical or negative, i.e., they represent Anthroposophy as elusive or undefinable. Interviewees can suggest that the lack of a clear Anthroposophical âbrandâ is a major reason for its current perceived crisis. An analysis of the ways in which Rudolf Steiner is portrayed in the interview material shows that there are a variety of descriptions of him rather than a unified representation of a charismatic leader that members can rally around. This, the study suggests, is because four different forms of charisma can be distinguished on theoretical grounds, and the particular form that permeates the narratives collected for this study does not readily support the dissemination of a centralized, dominant narrative.Antroposofiska SĂ€llskapet, grundat av österrikaren Rudolf Steiner, kom till Sverige redan i 1913, men för den generation av nutida svenska antroposofer vars röster hörs i denna studie intrĂ€ffade rörelsens stora blomstringstid först under nittonhundratalets andra hĂ€lft. Vid det laget hade rörelsen expanderat och blivit till en omfattande miljö med mĂ„nga stort sett oberoende institutioner och verksamheter, frĂ„n sjĂ€lva det Antroposofiska SĂ€llskapet i strikt mening till olika skolor, lantbruk, butiker, kliniker, osv., som alla byggde pĂ„ tolkningar av arvet efter Steiner. MĂ„nga medlemmar i rörelsen menar att det sedan dess har skett en nedgĂ„ng.
En rörelse med den storlek och komplexitet som det rör sig om i det aktuella fallet kan betraktas som en organisation med en företagsliknande struktur. Denna studie tar dÀrför sin utgÄngspunkt i ett organisationsteoretiskt perspektiv, i synnerhet i den gren av organisationsteorin som studerar berÀttande som ett led i hur en organisationskultur med mÄnga samexisterande röster skapas. I det aktuella fallet handlar det om berÀttelser som antroposofer i Sverige, bÄde vanliga medlemmar och personer i ledarstÀllning, framför om den blomstringstid de menar rörelsen en gÄng hade, den nedgÄng de sÀger sig uppleva och den framtid de förestÀller sig att antroposofin i Sverige kommer att möta. TjugoÄtta intervjuer genomfördes och de berÀttelser som förmedlas i dessa intervjuer analyserades med hjÀlp av en variant av den aktantmodell som utvecklats av semiotikern Algirdas Greimas.
Den grundlÀggande handling man Äterfinner i intervjupersonernas olika berÀttelser Àr att blomstringstiden var en guldÄlder dÄ karismatiska ledare kunde samla stora grupper av entusiastiska ungdomar och en levande antroposofisk miljö byggdes upp, men att denna guldÄlder upphörde nÀr ledarna gick ur tiden. Nuet, alltsÄ den tid dÄ intervjuerna genomfördes, beskrivs i berÀttelserna som en tid av förfall. Framtidsutsikterna som mÄlas upp i de flesta berÀttelser Àr dystra. Aktantanalysen visar att berÀttelserna om det förflutna bÄde beskriver denna tid i mycket positiva termer och nÀmner otaliga problem och konflikter. Nuets pÄstÄdda förfall Äterkommer i de flesta berÀttelser, men Äsikterna gÄr vitt isÀr nÀr det gÀller vad nutidens problem Àr och vad som orsakat dem. Framtiden beskrivs av vissa intervjupersoner som omöjlig att spekulera nÀrmare om, medan andra har specifika förslag till förÀndringar. Sammantaget visar analysen att det saknas en enhetlig förestÀllning om vad som behöver göras för att lösa rörelsens problem och vem som ska ta ansvar för dessa förÀndringar.
Intervjupersonerna Àr eniga om att antroposofin spelar en viktig roll. FrÄgan hur de skulle beskriva antroposofin och vad den har att erbjuda besvaras pÄ olika sÀtt, men sÀllan i termer av konkreta beskrivningar av för antroposofin centrala förestÀllningar eller praktiker. Tendensen Àr snarare att svara i metaforiska eller negativa termer, alltsÄ genom att berÀtta att de menar att antroposofin inte gÄr att definiera. Samtidigt kan intervjupersonerna förklara att bristen pÄ en tydlig antroposofisk identitet Àr ett huvudskÀl till vad de ser som rörelsens nuvarande kris. En analys av de sÀtt pÄ vilka Rudolf Steiner beskrivs i intervjumaterialet visar att det ocksÄ finns en rad divergerande uppfattningar av honom snarare Àn en sammanhÄllen beskrivning av en karismatisk ledare som medlemmarna kan samlas kring. Studien konkluderar att karisma pÄ teoretiska grunder kan delas in i fyra olika typer, och att den specifika form av karisma som intervjuerna Äterspeglar inte harmonierar sÀrskilt vÀl med spridandet av en centralt utformad dominerande berÀttelse
End(s) of the Harmonization in the European Union: Centrifuging or Engineering?
© 2021 Penn State University Press. All rights reserved. This work is licensed under Creative Commons Attribution CC-BY-NC-ND. https://creativecommons.org/licenses/by-nc-nd/4.0/The European Union (EU) harmonization has an evolving and dynamic nature. Different theoretical approaches (e.g., regulatory competition, coevolution, reflexive harmonization) are often echoed to delve into the EU harmonization. This article, going through these theories, endeavors to explain the harmonization discourse in the EU with a focus on the electronic communications sector. To understand the trajectory of the EU harmonization in this sector, two areas (ânetwork accessâ and âspectrum regulationâ) are selected as the subject-matter of the research. In conclusion, the legislative steps taken so far are found to restrict regulatory experimentation and innovation that this sector needs in the face of increasing challenges.Peer reviewedFinal Published versio
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Privacy-aware Smart Home Interface Framework
Smart home user interfaces are pervasive and shared by multiple users who occupy the space. Therefore, they pose a risk to interpersonal privacy of occupants because an individualâs sensitive information can be leaked to other co-occupants (information privacy), or they can be disturbed by intrusions into their personal space (physical privacy) when the co-occupant interacts with the smart home user interfaces. This thesis hypothesises that interpersonal privacy violations can be mitigated by adapting the user interface layer and presents insights into how to achieve usable user interface adaptation to mitigate or minimise interpersonal privacy violations in smart homes.
The thesis reports two case studies and two user studies. The first case study identifies the key characteristics needed to model the rich context of interpersonal privacy violations scenarios. Then it presents knowledge representation models that are required to represent the identified characteristics and evaluates them for adequacy in modelling the context information of interpersonal privacy violation scenarios. The second case study presents a software architecture and a set of algorithms that can detect interpersonal privacy violations and generate usable user interface adaptations. Then it evaluates the architecture and the algorithms for adequacy in generating usable privacy-aware user interface adaptations. The first user study (N=15) evaluates the usability of the adaptive user interfaces generated from the framework where storyboards were used as the stimulant. Extending the findings from the usability study and expanding the coverage of example scenarios, the second user study (N=23) evaluates the overall user experience of the adaptive user interfaces, using video prototypes as the stimulant.
The research demonstrates that the characteristics identified, and the respective knowledge representation models adequately captured the context of interpersonal privacy violation scenarios. Furthermore, the software architecture and the algorithms could detect possible interpersonal privacy violations and generate usable user interface adaptations to mitigate them. The two user studies demonstrate that the adaptive user interfaces, when used in appropriate situations, were a suitable solution for addressing interpersonal privacy violations while providing high usability and a positive user experience. The thesis concludes by providing recommendations for developing privacy-aware user interface adaptations and suggesting future work that can extend this research
Distributed Hâ Controller Design and Robustness Analysis for Vehicle Platooning Under Random Packet Drop
This paper presents the design of a robust distributed state-feedback controller in the discrete-time domain for homogeneous vehicle platoons with undirected topologies, whose dynamics are subjected to external disturbances and under random single packet drop scenario. A linear matrix inequality (LMI) approach is used for devising the control gains such that a bounded Hâ norm is guaranteed. Furthermore, a lower bound of the robustness measure, denoted as Îł gain, is derived analytically for two platoon communication topologies, i.e., the bidirectional predecessor following (BPF) and the bidirectional predecessor leader following (BPLF). It is shown that the Îł gain is highly affected by the communication topology and drastically reduces when the information of the leader is sent to all followers. Finally, numerical results demonstrate the ability of the proposed methodology to impose the platoon control objective for the BPF and BPLF topology under random single packet drop
Adaptive task selection using threshold-based techniques in dynamic sensor networks
Sensor nodes, like many social insect species, exist in harsh environments in large groups, yet possess very limited amount of resources. Lasting for as long as possible, and fulfilling the network purposes are the ultimate goals of sensor networks. However, these goals are inherently contradictory. Nature can be a great source of inspiration for mankind to find methods to achieve both extended survival, and effective operation. This work aims at applying the threshold-based action selection mechanisms inspired from insect societies to perform action selection within sensor nodes. The effect of this micro-model on the macro-behaviour of the network is studied in terms of durability and task performance quality. Generally, this is an example of using bio-inspiration to achieve adaptivity in sensor networks
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