Planning for Decentralized Control of Multiple Robots Under Uncertainty

We describe a probabilistic framework for synthesizing control policies for general multi-robot systems, given environment and sensor models and a cost function. Decentralized, partially observable Markov decision processes (Dec-POMDPs) are a general model of decision processes where a team of agents must cooperate to optimize some objective (specified by a shared reward or cost function) in the presence of uncertainty, but where communication limitations mean that the agents cannot share their state, so execution must proceed in a decentralized fashion. While Dec-POMDPs are typically intractable to solve for real-world problems, recent research on the use of macro-actions in Dec-POMDPs has significantly increased the size of problem that can be practically solved as a Dec-POMDP. We describe this general model, and show how, in contrast to most existing methods that are specialized to a particular problem class, it can synthesize control policies that use whatever opportunities for coordination are present in the problem, while balancing off uncertainty in outcomes, sensor information, and information about other agents. We use three variations on a warehouse task to show that a single planner of this type can generate cooperative behavior using task allocation, direct communication, and signaling, as appropriate

Designing Sugaropolis:digital games as a medium for conveying transnational narratives

In this paper, the authors present a case study of ‘Sugaropolis’: a two-year practice-based project that involved interdisciplinary co-design and stakeholder evaluation of two digital game prototypes. Drawing on the diverse expertise of the research team (game design and development, human geography, and transnational narratives), the paper aims to contribute to debates about the use of digital games as a medium for representing the past. With an emphasis on design-as-research, we consider how digital games can be (co-)designed to communicate complex histories and geographies in which people, objects, and resources are connected through space and time

A decidable policy language for history-based transaction monitoring

Online trading invariably involves dealings between strangers, so it is important for one party to be able to judge objectively the trustworthiness of the other. In such a setting, the decision to trust a user may sensibly be based on that user's past behaviour. We introduce a specification language based on linear temporal logic for expressing a policy for categorising the behaviour patterns of a user depending on its transaction history. We also present an algorithm for checking whether the transaction history obeys the stated policy. To be useful in a real setting, such a language should allow one to express realistic policies which may involve parameter quantification and quantitative or statistical patterns. We introduce several extensions of linear temporal logic to cater for such needs: a restricted form of universal and existential quantification; arbitrary computable functions and relations in the term language; and a "counting" quantifier for counting how many times a formula holds in the past. We then show that model checking a transaction history against a policy, which we call the history-based transaction monitoring problem, is PSPACE-complete in the size of the policy formula and the length of the history. The problem becomes decidable in polynomial time when the policies are fixed. We also consider the problem of transaction monitoring in the case where not all the parameters of actions are observable. We formulate two such "partial observability" monitoring problems, and show their decidability under certain restrictions

No. 3 adhesives in textile conservation: a select annotated bibliography of references about adhesives in textile conservation compiled by Karen Thompson

A select annotated bibliography of references about Adhesives in Textile Conservation, compiled by Karen Thompson. The aim of the Chantry Library Subject Bibliographies is to support the work of Icon members, by providing an up-to-date list of the most relevant source material on a topic in conservation with annotations giving information about the relevance, accuracy and quality of the sources cited, making it easier to evaluate the literature on a given subject. The Bibliographies have been compiled by recognized specialists, who have selected the key works in their field of specialism. This bibliography, the third in our series, provides a compilation of selected references about the use of adhesives in textile conservation. Drawing on specialist knowledge from research and best practice at the Centre for Textile Conservation at the University of Glasgow, the references reflect much of the current thinking and issues in this area of expertise and specialism

On Many-Minds Interpretations of Quantum Theory

This paper is a response to some recent discussions of many-minds interpretations in the philosophical literature. After an introduction to the many-minds idea, the complexity of quantum states for macroscopic objects is stressed. Then it is proposed that a characterization of the physical structure of observers is a proper goal for physical theory. It is argued that an observer cannot be defined merely by the instantaneous structure of a brain, but that the history of the brain's functioning must also be taken into account. Next the nature of probability in many-minds interpretations is discussed and it is suggested that only discrete probability models are needed. The paper concludes with brief comments on issues of actuality and identity over time.Comment: 16 pages, plain TeX, no macros required. Revised following comments November 199

Philosophical Implications of Inflationary Cosmology

Recent developments in cosmology indicate that every history having a nonzero probability is realized in infinitely many distinct regions of spacetime. Thus, it appears that the universe contains infinitely many civilizations exactly like our own, as well as infinitely many civilizations that differ from our own in any way permitted by physical laws. We explore the implications of this conclusion for ethical theory and for the doomsday argument. In the infinite universe, we find that the doomsday argument applies only to effects which change the average lifetime of all civilizations, and not those which affect our civilization alone.Comment: 25 pages; v2: revised version to appear in British Journal for the Philosophy of Scienc

An Impossible object? Ecological Democracy after the Anthropocene

El paper se pregunta en qué medida la democracia -o sea, una democracia ecológica- puede ocuparse del Antropoceno, la nueva era geológica que describe una masiva penetración humana en los sistemas naturales.Universidad de Málaga. Campus de Excelencia Andalucía Tec

A Formal Framework for Concrete Reputation Systems

In a reputation-based trust-management system, agents maintain information about the past behaviour of other agents. This information is used to guide future trust-based decisions about interaction. However, while trust management is a component in security decision-making, many existing reputation-based trust-management systems provide no formal security-guarantees. In this extended abstract, we describe a mathematical framework for a class of simple reputation-based systems. In these systems, decisions about interaction are taken based on policies that are exact requirements on agents’ past histories. We present a basic declarative language, based on pure-past linear temporal logic, intended for writing simple policies. While the basic language is reasonably expressive (encoding e.g. Chinese Wall policies) we show how one can extend it with quantification and parameterized events. This allows us to encode other policies known from the literature, e.g., ‘one-out-of-k’. The problem of checking a history with respect to a policy is efficient for the basic language, and tractable for the quantified language when policies do not have too many variables