Cooperative Constraint Research Articles

Diversity-Multiplexing Tradeoff of Fading Interference Channels With Source Cooperation and Partial CSIT

In this paper, diversity-multiplexing tradeoff (DMT) of the delay-limited symmetric two-user single-antenna fading interference channel (IFC) with source cooperation is evaluated under both full-duplex and half-duplex cooperation constraints. The interference signal and the desired signal received by each destination node are assumed to be of comparable strength. Under each cooperation constraint, DMT upper and lower bounds are derived and shown to be tight, i.e., the lower bound meets the upper bound. A full characterization of the DMT of the channel is thus established. The upper bounds are evaluated using the capacity upper bounds and the lower bounds are obtained based on our proposed transmission schemes. The proposed transmission schemes only require partial channel state information at transmitter side (CSIT), making them suitable for practical applications. Specifically, for the transmission scheme designed under the full-duplex constraint, the partial CSIT is obtained by letting each destination represent the fading magnitude of each of its incoming links using 1 bit of information and feed back this information to the sources. In the half-duplex case, the proposed transmission scheme requires no more than 3 bits of feedback information to represent the fading magnitude of each link. Our DMT results show that source cooperation can notably improve the system diversity performance over the whole multiplexing gain region even under the half-duplex constraint.

A Theoretical Framework for the Higher-Order Cooperation of Numeric Constraint Domains

This paper presents a theoretical framework for the integration of the cooperative constraint solving of numeric constraint domains into higher-order functional and logic programming on λ-abstractions, using an instance of a generic Constraint Functional Logic Programming (CFLP) scheme over a so-called higher-order coordination domain. We provide this framework as a powerful computational model for the higher-order cooperation of algebraic constraint domains over real numbers and integers, which has been useful in practical applications involving the hybrid combination of its components, so that more declarative and efficient solutions can be promoted. Our proposal of computational model has been proved sound and complete with respect to the declarative semantics provided by the CFLP scheme, and enriched with new mechanisms for modeling the intended cooperation among the numeric domains and a novel higher-order constraint domain equipped with a sound and complete constraint solver for solving higher-order equations. We argue the applicability of our approach describing a prototype implementation on top of the constraint functional logic system TOY.

Distributed model predictive control for multi-agent systems with coupling constraints

This paper proposes an improved distributed model predictive control (DMPC) scheme for multi-agent systems with coupling constraints by applying compatibility constraint and deviation penalisation. Firstly, a sufficient condition based on the compatibility constraint to satisfying cooperative coupling constraints is given, which enables control performance and coupling constraints dependent on the compatibility constraint. Then, in order to optimise the control trajectory and to improve the consistency of the actions between agents, the deviation between what an agent is actually doing and what its neighbours believe it is doing is penalised in the cost function. At each sampling instant, the compatibility constraint of each agent is set tighter than the previous sampling instant. The optimal control problem is formulated as quadratic programming with quadratic constraints. Finally, two simulation examples are given to illustrate the effectiveness of the proposed scheme.

A Constraint Based Decision Support System for Deadlocks Resolution in Collaborative New Product Design

In this paper we are considering that the product modelling step of a new product design process can be represented as a CSP (Constraint Satisfaction Problem). CSP modelling and resolution has proved its efficiency within the framework of single-designer design. We propose to extend the functions of CSP to the context of multi-designers. We have recently defined CoCSP as Cooperative Constraint Satisfaction Problem including the actors of the design problem. We present the operating principles of a new algorithm to solve the deadlocks appearing between constraints in a new product modelling process. Our reasoning is based on a model described in the form of a CoCSP. At each step, the algorithm generates the sets of consistent decisions, maximizing their cardinality. The algorithm forms the core of a prototype for an unsupervised, generic constraint-based collaborative decision support system. The work is illustrated by the example of a car engine collaborative modelling process.

Außer Spesen nichts gewesen?


 
 
 Stakeholders in public authorities are often sceptical towards cross-border cooperation projects in spatial development. The reason for this is that the benefit too often remains unclear, even after the closure of such processes that are in many cases funded by EU Programmes. A reasonable expenditure of European subsidies for cross-border cooperation becomes a challenge. But it is up to the stakeholders themselves to benefit from the achieved results of cooperation. This requires a longterm perspective, joint and realistic objectives and expectations as well as skills for dealing with existing constraints of cooperation.
 
 
 
 
 

A CSP approach for the network of product lifecycle constraints consistency in a collaborative design context

In this paper, we are considering that the design process can be modelled in the form of a constraint satisfaction problem (CSP). CSP modelling or resolution has proved its efficiency within the framework of single-designer design. We propose to extend the functions of CSP to the context of multi-concept design of the same artefact. We define CoCSP as cooperative constraint satisfaction problem including the actors of the design problem. We are presenting the operating principles of an algorithm for the real-time management of design decisions, based on a model described in the form of a CoCSP for the integration of supply-chain constraints. This algorithm enables the number of design decisions rejected at a given moment in design to be kept to a minimum. The algorithm forms the core of a prototype for an unsupervised, generic constraint-based collaborative design system. Our aim is to produce a platform centred on the notion of constraints that will enable a product design problem to be modelled and solved by integrating supply-chain constraints as far upstream as possible.

The Political Economy of Chinese-Style Privatization: Motives and Constraints

The paper examines how the privatization of Chinese state-owned enterprises (SOEs) can be successfully triggered and completed. By identifying the motives of local government leaders and the constraints that face them during transition, we conclude that: first, whether local governments are motivated to privatize their SOEs, depends on if the ownership transfer is expected to stimulate sufficiently high growth of local tax revenues without sacrificing the bureaucrats private control benefits. Second, a specific privatization program can succeed only if it manages to satisfy the managerial cooperation constraint, the workers compensation constraint, and the bank-debt-servicing constraint. The motives-cum-constraints political economy approach offers an important explanation for the pace and scope of the ongoing Chinese-style privatization.

Decentralized Cooperative Aerial Surveillance Using Fixed-Wing Miniature UAVs

Numerous applications require aerial surveillance. Civilian applications include monitoring forest fires, oil fields, and pipelines and tracking wildlife. Applications to homeland security include border patrol and monitoring the perimeter of nuclear power plants. Military applications are numerous. The current approach to these applications is to use a single manned vehicle for surveillance. However, manned vehicles are typically large and expensive. In addition, hazardous environments and operator fatigue can potentially threaten the life of the pilot. Therefore, there is a critical need for automating aerial surveillance using unmanned air vehicles (UAVs). This paper gives an overview of a cooperative control strategy for aerial surveillance that has been successfully flight tested on small (48-in wingspan) UAVs. Our approach to cooperative control problems can be summarized in four steps: 1) the definition of a cooperation constraint and cooperation objective; 2) the definition of a coordination variable as the minimal amount of information needed to effect cooperation; 3) the design of a centralized cooperation strategy; and 4) the use of consensus schemes to transform the centralized strategy into a decentralized algorithm. The effectiveness of the solution will be shown using both high-fidelity simulation and actual flight tests

Hans Bethe: Superlative Scientist, Incomparable Mentor, Humanitarian, Friend

Hans Bethe: Superlative Scientist, Incomparable Mentor, Humanitarian, Friend

A Typology of Regional Cooperation Projects

Regional cooperation projects between countries in the Middle East are expected to provide benefits to all parties involved but their feasibility is subject to social, economic and political constraints. This article uses a database of planned projects in the last decade and tries to detect types of projects that are less sensitive to the constraints. A typology of projects shows the prevalence of two main groups. A first group of projects avoids constraints by focusing on relatively high micro-economic viability but with low intensity of cooperation: these are economic-business projects and some infrastructure projects that are based on mere coordination between countries and mostly implemented separately in a single country. A second group of projects are infrastructure and public services projects that involve a number of countries, and implementation through joint planning and management. We conclude that the response to the constraints for regional cooperation is found in the concentration in projects that do not require any intensive continuous contact between the populations, by choosing business projects that are implemented separately in each country, or public projects that are jointly implemented, but on the basis of cooperation between public officers, not necessarily the population.

Dynamics of end-tethered chains at high surface coverage

A molecular model for wall slip [Y. M. Joshi et al., Macromolecules 34, 3412 (2001)] based on recent tube theories is extended to account for the effects of entanglements between tethered chains that occur at higher surface coverage. Three regimes of surface coverage are identified. Regime I is a low surface coverage regime (the mushroom regime), which has been discussed earlier by us. In regime II the tethered chains undergo a cooperative constraint release process due to which the slip velocity increases with surface coverage while the slip length becomes independent of the surface coverage. In regime III the tethered chains start to become entangled with each other thereby causing the interfacial modulus, the critical wall shear stress and the critical shear rate to decrease with surface coverage. Our model is different from previous scaling models in that it provides a constitutive equation for tethered chains. As a result, it offers scope for quantitative prediction of microscopic and macroscopic experimental slip data based solely on molecular information. Our model also predicts scaling laws for the various slip parameters in the three regimes of surface coverage. These laws are in general agreement with previously reported scaling models and experimental data.

Learning Sequences of Compatible Actions Among Agents

Action coordination in multiagent systems is a difficult task especially in dynamic environments. If the environment possesses cooperation, least communication, incompatibility and local information constraints, the task becomes even more difficult. Learning compatible action sequences to achieve a designated goal under these constraints is studied in this work. Two new multiagent learning algorithms called QACE and NoCommQACE are developed. To improve the performance of the QACE and NoCommQACE algorithms four heuristics, state iteration, means-ends analysis, decreasing reward and do-nothing, are developed. The proposed algorithms are tested on the blocks world domain and the performance results are reported.

Optimal defence structure for a small country

Small countries may not be able to afford all force elements (army, navy, air-force) operated by larger countries and certainly cannot afford all sub-elements (aircraft carriers, submarines, etc). This paper provides a framework for a small country to analyse its force structure, examining the influence of objectives, international co-operation, funding and technological constraints, and uncertainty. We analyse when a small country may choose to retain a balanced structure (with each force element) and when it may choose to drop one or more elements. The issues are illustrated with the decision by the New Zealand government over whether to retain a strike aircraft capacity.

Distributed Semantic Constraints in Virtual Enterprise Information Integrating Systems

With the explosive growth of the Worldwide Web, research on constraints in different databases has become increasingly important. How to interoperate heterogeneous Virtual Enterprise (VE) information sources, and how to enforce enterprise logic across multi-enterprise information sources are problems attracting some attention. The existing approaches defined enterprise logic in advance that result in poor flexibility, reusability and practicability. In order to solve these problems, a cooperative constraint description for different kinds of distributed constraints is proposed. The constraints classification has been done through the Constraint Definition Language LC. In order to manage these constraints among different enterprise information sources effectively, the properties of distributed constraints are presented, and Active Rules are incorporated to support constraints of enterprise-wide information processing. Further, some novel implementation issues including classifying enterprise event, static and dynamic definition methods for Enterprise Event Object (EEO) and the scheduler model in a CORBA based VE information integrating system, ViaScope, are presented.

An open environment for cooperative equational solving

We describe a system called CFLP which aims at the integration of the best features of functional logic programming (FLP), cooperative constraint solving (CCS), and distributed computing. FLP provides support for defining one’s own abstractions over a constraint domain in an easy and comfortable way, whereas CCS is employed to solve systems of mixed constraints by iterating specialized constraint solving methods in accordance with a well defined strategy. The system is a distributed implementation of a cooperative constraint functional logic programming scheme that combines higher-order lazy narrowing with cooperative constraint solving. The model takes advantage of the existence of several constraint solving resources located in a distributed environment (e. g., a network of computers), which communicate asynchronously via message passing. To increase the openness of the system, we are redesigning CFLP based on CORBA. We discuss some design and implementation issues of the system.

Coordination of heterogeneous distributed cooperative constraint solving

In this paper we argue for an alternative way of designing cooperative constraint solver systems using a control-oriented coordination language. The idea is to take advantage of the coordination features of MANIFOLD for improving the constraint solver collaboration language of BALI . We demonstrate the validity of our ideas by presenting the advantages of such a realization and its (practical as well as conceptual) improvements of constraint solving. We are convinced that cooperative constraint solving is intrinsically linked to coordination, and that coordination languages, and MANIFOLD in particular, open new horizons for systems like BALI .

Bayesian Environmental Policy Decisions: Two Case Studies

Statistical decision theory can be a valuable tool for policy‐making decisions. In particular, environmental problems often benefit from the application of Bayesian and decision‐theoretic techniques that address the uncertain nature of problems in the environmental and ecological sciences. This paper discusses aspects of implementing statistical decision‐making tools in situations where uncertainty is present, looking at issues such as elicitation of prior distributions, covariate allocation, formulation of loss functions, and minimization of expected losses subject to cooperation constraints. These ideas are illustrated through two case studies in environmental remediation.

Object‐Oriented Protocol Hierarchies for Distributed Workflow Systems

Modern information systems will increasingly have to support the cooperation between more or less independent partners that are distributed across local or global networks. Since the partners can naturally be modeled by objects, means must be provided that permit to model the cooperation among objects. In this paper we propose an extended object model which allows the explicit definition of dynamic relationships between objects. The new construct, called alliances, can be viewed as a protocol that materializes and enforces the cooperation of an arbitrary number of objects by relying on a set of communication rules. The rule‐based approach allows to specify cooperation protocols which circumscribe a space of possible cooperations. In other words, cooperation protocols restrict cooperation among objects to the minimum extent needed to leave the objects enough leeway for spontaneous reactions while still guaranteeing that the constraints inherent in a cooperation on a common task are being met. Workflows are specifications of cooperative applications. We demonstrate how alliances can be used as an implementation model for distributed workflow systems, which is superior to a pure object‐based implementation. This suggests that alliances are a lower‐level, more implementation‐oriented support structure for workflows. In particular, it should be possible to derive the cooperation constraints of an alliance from higher‐level workflow specifications which model business processes. Alliances can in turn be implemented on top of common distributed object technology which for its part relies on standard database and communication services.