Towards application-level elasticity on shared cluster: an actor-based approach

In current cluster computing, several distributed frameworks are designed to support elasticity for business services adapting to environment fluctuation. However, most existing works support elasticity mainly at the resource level, leaving application level elasticity support problem to domain-specific frameworks and applications. This paper proposes an actor-based general approach to support application-level elasticity for multiple cluster computing frameworks. The actor model offers scalability and decouples language-level concurrency from the runtime environment. By extending actors, a new middle layer called Unisupervisor is designed to “sit” between the resource management layer and application framework layer. Actors in Unisupervisor can automatically distribute and execute tasks over clusters and dynamically scale in/out. Based on Unisupervisor, high-level profiles (MasterSlave, MapReduce, Streaming, Graph, and Pipeline) for diverse cluster computing requirements can be supported. The entire approach is implemented in a prototype system called UniAS. In the evaluation, both benchmarks and real applications are tested and analyzed in a small scale cluster. Results show that UniAS is expressive and efficiently elastic.     

Linguistic symbiosis between event loop actors and threads

In modern programming languages, concurrency control can be traced back to one of two different schools: actor-based message passing concurrency and thread-based shared-state concurrency. This paper describes a linguistic symbiosis between two programming languages with such different concurrency models. More specifically, we describe a novel symbiosis between actors represented as event loops on the one hand and threads on the other. This symbiosis ensures that the invariants of the actor-based concurrency model are not violated by engaging in symbiosis with multithreaded programs. The proposed mapping is validated by means of a concrete symbiosis between AmbientTalk, a flexible, domain-specific language for writing distributed programs and Java, a conventional object-oriented language. This symbiosis allows the domain-specific language to reuse existing software components written in a multithreaded language without sacrificing the beneficial event-driven properties of the actor concurrency model.     

带执行器节点的无线传感器网络的分簇算法

带执行器节点的无线传感器网络(WSAN)是指在无线传感器网络中加入执行器,传感器用于检测物理环境信息,执行器收集和处理这些检测数据,并作出适当的执行任务。传感器和执行器的协作是WSAN研究的一个重要内容,就此提出了一个动态分簇算法,根据事件发生的实际情况,仅仅对该事件区域分簇,每个簇包括一个执行器节点以及传送数据到该执行器节点的传感器节点。通过这种分簇,可以决定传感器与哪个执行器通信以及路由方式。     

A companion modeling approach applied to fishery management

Don Hoi Lord, a coastal wetland in the upper gulf of Thailand, is famous for the razor clam (Solen regularis), which is a source of food and income for local fishermen. However, the razor clam population is significantly decreasing so the aim of this study was to analyze the razor clam fishery and develop a management plan engaging the different stakeholders in collective discussions. A participatory modelling approach was used, including (a) agent-based modelling (ABM) and (b) role-playing games (RPG). First, an individual-state distribution model of the razor clam population was designed and calibrated to synthesise knowledge. Two RPG sessions supported by this biological model were organised to initiate collective learning and promote discussion among stakeholders. After playing with the baseline scenario showing the actual harvesting situation, discussions led to the definition of alternative scenarios for clam management such as establishment and rotation of zones closed for harvesting, and quota systems. These scenarios developed during the RPG sessions were more deeply investigated with an agent-based model that included fishermen agents and the individual-state distribution model of the razor clam population. Simulations of different scenarios (reserve, quota and combination of reserve and quota) were produced to enable better informed discussion between different stakeholders. Stakeholders have acknowledged that management through rotating reserves is not efficient if the duration of reserves is too short. They have realised that the efficiency of reserves is hard to assess without better data on clam recruitment. They have also explored another management option which is the quota system. In the final stage, the local participatory process was endorsed by the incumbent regional policy-making actor. Unfortunately, because of rapid administrative rotation the project abruptly lost support. This unexpected event emphasises the need for continuous monitoring of all actors entering and/or leaving the system, which can radically change the interactions among them and, therefore, the whole management context.     

传感反应网络中单反应节点任务分配问题的研究

无线传感反应网络由大量资源受限的传感节点和少量资源丰富的反应节点通过无线通信自主形成的。其中,传感节点负责收集外界的事件信息,而反应节点依据传感节点探测到的信息做出决策,并对外界做出响应。本文主要研究WSANs中单反应节点任务分配的问题,并提出集中式和分布式两种算法,最后用J-Sim评估两种算法的性能。     

Cognitive development and qualitative modelling

This paper argues that in order to encourage the learning of high level cognitive skills through the use of computers, it is necessary to use systems which are adapted to forms of natural human reasoning. This is specifically the case in using modelling programs. Two kinds of such reasoning are identified, both qualitative: reasoning using imagined objects and events, and semi-quantitative reasoning. Modelling systems which support each form are described. Some results of research with them are outlined.     

A dynamic assessment tool for exploring and communicating vulnerability to floods and climate change

In this article we propose an innovative approach to support a participatory modelling process for the exploratory assessment of vulnerability within the broad context of climate change adaptation. The approach provides a simplified dynamic vulnerability model developed within a conceptual model adopted – but very rarely made operational – by many international organisations such as the Intergovernmental Panel for Climate Change, the European Union. We propose a procedure in which disciplinary experts and local actors interact for the identification of the most relevant issues with reference to a specific vulnerability problem. Local actors (e.g. representatives of public administrations, business, NGOs) identify the most relevant issues related to the various dimensions of vulnerability, to be considered as input variables to contextualise the generalised model in the study case. Quantitative indicators are provided by disciplinary experts to describe past and future trends of variables, and their trajectories are combined to explore possible future vulnerability trends and scenarios. A non additive aggregation operator is proposed to allow experts and actors to pro vide their preferences through ad hoc questionnaires, thus overcoming the oversimplifications of most of the current vulnerability indices, which are usually either additive (fully compensatory) or multiplicative (non compensatory), and providing transparent and robust management of subjectivity and analysis of the deriving variability and uncertainty in model outputs. Input data for the demonstration of the model derive from the European Project Brahmatwinn, with reference to the Assam State in India.     

Clustering of wireless sensor and actor networks based on sensor distribution and connectivity

Wireless Sensor and Actor Networks (WSANs) employ significantly more capable actor nodes that can collect data from sensors and perform application specific actions. To take these actions collaboratively at any spot in the monitored regions, maximal actor coverage along with inter-actor connectivity is desirable. In this paper, we propose a distributed actor positioning and clustering algorithm which employs actors as cluster-heads and places them in such a way that the coverage of actors is maximized and the data gathering and acting times are minimized. Such placement of actors is done by determining the k-hop Independent Dominating Set (IDS) of the underlying sensor network. Basically, before the actors are placed, the sensors pick the cluster-heads based on IDS. The actors are then placed at the locations of such cluster-heads. We further derive conditions to guarantee inter-actor connectivity after the clustering is performed. If inter-connectivity does not exist, the actors coordinate through the underlying sensors in their clusters to adjust their locations so that connectivity can be established. The performances of the proposed approaches are validated through simulations.     

Participatory Bayesian modelling for sustainable and efficient river restoration projects: Feedback from the case study of the Gave de Pau River,Hautes‐Pyrénées,France

Through the diversity of criteria and stakes, the uncertain nature of the entailed phenomena and the multi‐scale aspects to be taken into account, a river restoration project can be considered as a complex problem. Integrative approaches and modelling tools are thus needed to help river managers make predictions on the evolution of hydromorphological, socio‐economic, safety and ecological issues. Such approach can provide valuable information for handling long‐term management plans that consider the interaction and the balance of stakeholders interests and river system functioning. In this paper, we present a probabilistic participatory modelling (PM) method that assesses the effects of given restoration actions, knowing the hydromorphological modifications that they may induce on the safety, ecological and socio‐economic aspects with the help of local stakeholders through several workshops. To support this strategy, we used Bayesian networks (BNs) as modelling tools as their causal graphs can combine multidimensional knowledge and data from diverse natures. We introduce the causal graphs elaborated with the help of the stakeholders and convert it into BNs that can assist restoration decisions by considering the available decision and utility functions to provide guidance to decision‐makers. This was applied to the “Lac des Gaves” reach in the Hautes‐Pyrénées, France, a reach that has gone through severe sediment extractions for over 50 years. Each network represents possible restoration decisions linked to one of the observed issues. The paper demonstrates how BNs used as a decision support system (DSS) can help to assess the influence of given management strategies on the river system with the consideration of stakeholders’ knowledge and integration in all the modelling process.     

Formal modeling of evolving self-adaptive systems

In this paper, we present a formal model, named PobSAM (Policy-based Self-Adaptive Model), for developing and modeling self-adaptive evolving systems. In this model, policies are used as a mechanism to direct and adapt the behavior of self-adaptive systems. A PobSAM model is a collection of autonomous managers and managed actors. The managed actors are dedicated to the functional behavior while the autonomous managers govern the behavior of managed actors by enforcing suitable policies. A manager has a set of configurations including two types of policies: governing policies and adaptation policies. To adapt the system behavior in response to the changes, the managers switch among different configurations. We employ the combination of an algebraic formalism and an actor-based model to specify this model formally. Managed actors are expressed by an actor model. Managers are modeled as meta-actors whose configurations are described using a multi-sorted algebra called CA. We provide an operational semantics for PobSAM using labeled transition systems. Furthermore, we provide behavioral equivalence of different sorts of CA in terms of splitting bisimulation and prioritized splitting bisimulation. Equivalent managers send the same set of messages to the actors. Using our behavioral equivalence theory, we can prove that the overall behavior of the system is preserved by substituting a manager by an equivalent one.     

Maximizing connected coverage via controlled actor relocation in wireless sensor and actor networks

Wireless sensor and actor networks (WSANs) have recently emerged with the idea of combining wireless sensor networks (WSNs) and mobile ad hoc networks (MANETs). In addition to resource constrained sensors, resource rich and mobile actor nodes are employed in WSANs. These actors can collect data from the sensors and perform appropriate actions as a result of processing such data. To perform the actions at all parts of the region in a timely manner, the actors should be deployed in such a way that they might be able to communicate with each other and cover the whole monitored area. This requires that the actors should be placed carefully prior to network operation in order to maximize the coverage and maintain the inter-actor connectivity. In this paper, we propose a distributed actor deployment algorithm that strives to maximize the coverage of actors without violating the connectivity requirement. The approach applies repelling forces between neighboring actors and from the sensors that sit on the boundaries in order to spread them in the region. The spreading of the nodes is done using a tree of actors which can provide more freedom for the movement of the nodes but at the same time maintain the required connectivity among the nodes. We present two techniques for creation of such an actor tree which are based on local pruning of the actor links and spanning tree of the inter-actor network. The performance of our approach is validated both analytically and experimentally.     

How do you perceive environmental change? Fuzzy Cognitive Mapping informing stakeholder analysis for environmental policy making and non-market valuation

In spite of considerable progress in our understanding of ecosystem functioning, our ability to design effective and enforceable environmental policies requires a deep understanding of human perceptions and beliefs. In this respect, what is called today stakeholder analysis is an eclectic mixture of qualitative and semi-quantitative techniques aiming at eliciting, understanding and de-codifying how individuals perceive risks and threats towards sustainability. Fuzzy Cognitive Mapping (FCM) is gradually emerging as an alternative methodology capable of assisting researchers in the domain of environmental policy. We explored the promise that FCM holds to support environmental policy makers. We suggest FCM approach as a new participatory method in environmental policy: through aiding in Multi-stakeholder (actor) analysis for risk assessment, capturing values and scenarios construction. To show how this is feasible we try to answer three basic questions: How cognitive mapping can support decision-making? How FCM can support environmental decision-making? How simulation of concepts may help in communicating stakeholders’ views to environmental decision makers? Then we explore the potential application of FCM in environmental policy, especially in environmental economics, trying to substantiate economic values for nature providing ‘flesh and bones’ to the concept of economic preferences.     

Defining assessment projects and scenarios for policy support: Use of ontology in Integrated Assessment and Modelling

Integrated Assessment and Modelling (IAM) provides an interdisciplinary approach to support ex-ante decision-making by combining quantitative models representing different systems and scales into a framework for integrated assessment. Scenarios in IAM are developed in the interaction between scientists and stakeholders to explore possible pathways of future development. As IAM typically combines models from different disciplines, there is a clear need for a consistent definition and implementation of scenarios across models, policy problems and scales. This paper presents such a unified conceptualization for scenario and assessment projects. We demonstrate the use of common ontologies in building this unified conceptualization, e.g. a common ontology on assessment projects and scenarios. The common ontology and the process of ontology engineering are used in a case study, which refers to the development of SEAMLESS-IF, an integrated modelling framework to assess agricultural and environmental policy options as to their contribution to sustainable development. The presented common ontology on assessment projects and scenarios can be reused by IAM consortia and if required, adapted by using the process of ontology engineering as proposed in this paper.     

Values in socio-environmental modelling: Persuasion for action or excuse for inaction

Science in general and modelling in particular provide in-depth understanding of environmental processes and clearly demonstrate the present unsustainable use of resources on a global scale. The latest report by the Intergovernmental Panel on Climate Change (IPCC), for instance, shows that climate is changing and with a 95% certainty it is the humans have caused the change. The future climatic conditions are shown to be largely adversely affecting human wellbeing on this planet. Yet we see in numerous examples that societies are very slow in reacting to this rapid depletion of natural resources. What still seems lacking is the translation of scientific reports and the results of analysis and modelling into corrective actions. We argue that one of the reasons for this is the traditional workflow of environmental modelling, which starts with the purpose, the goal formulation, and ends with problem solutions or decision support tools. Instead, modelling, and applied science in general, has to enhance its scope beyond the problem solving stage, to do more on the problem definition and solution implementation phases. Modelling can be also used for identification of societal values and for setting purposes by appropriate communication of the modelling process and results. We believe this new approach for modelling can impact and bring the social values to the forefront of socio-environmental debate and hence turn scientific results into actions sooner rather than later. Instead of being separated from the modelling process, the translation of results should be an intrinsic part of it. We discuss several challenges for recent socio-environmental modelling and conclude with ten propositions that modellers and scientists in general can follow to improve their communication with the society and produce results that can be understood and used to improve awareness and education and spur action.     

TSLBS: A Time-Sensitive and Load Balanced Scheduling Approach to Wireless Sensor Actor Networks

Existing works on scheduling in Wireless Sensor Actor Networks (WSANs) are mostly concerned with energy savings and ignore time constraints and thus increase the make-span of the network. Moreover, these algorithms usually do not consider balance of workloads on the actor nodes and hence, sometimes some of the actors are busy when some others are idle. These problem causes the actors are not utilized properly and the actors’ lifetime is reduced. In this paper we take both time awareness and balance of workloads on the actor in WSANs into account and propose a convex optimization model (TAMMs) to minimize make-span. We also propose a protocol called LIBP to improve load balancing that allocates tasks to actors according to their measured capabilities in such a way to enhance balances of workloads on the actors. Finally, by combination of TAMMs and LIBP, a time-sensitive and load balanced scheduling approach (TSLBS) is proposed. TSLBS considers both local and global tasks and the distribution requirements of WSANs (i.e. WSANs with hybrid architecture). The results of simulations on typical scenarios shows that TSLBs is more efficient in terms of both the make-span and load balancing compared to stochastic task scheduling algorithm (STSA). We also show that TSLBs performs significantly better than STSA in terms of actor’s lifetime.     

Integrated design and collaborative engineering of fabric structures

The design of fabric structures incorporates specfic aspects due to the tight interdependency between geometric, mechanical and manufacturing data used by the different professional partners. This is highlighted through the analysis of the various steps of the design process. A design approach, that takes into account the various actors, their knowledge and the techniques available within each of the previous fields has been set up.This approach relies on the identification of the flow of information and on the organization of data sets that are compatible with the design process breakdown into tasks in order to preserve their integration. Approximation methods are associated with some of this information to create design phases adapted to each actor through software tools implementing various modelling processes. The form finding process, the mechanical analysis of the structure, the determination of cutting patterns are examples of such modelling processes. The surface model of the fabric structure is one of such sets of data which has been identified and used to preserve the integration of the design process.Associated with the integrated design architecture, a collaborative environment helps to set up communication between some of the actors according to the design process organization. This environment acts as a complementary tool to help seeking compromises among the actors participating in a given phase of the design process. The communication tools work on a distributed architecture in such a manner that dialogue objects are shared among the actors.     

Participatory land use modelling,pathways to an integrated approach

The increasing adoption of land use models in planning and policy development highlights the need for an integrated approach that combines analytical modelling techniques with discursive ‘soft-science’ methodologies. Recent scientific contributions to the discipline have tended to focus on analytical problems such as statistical assessment of model goodness of fit through map comparison techniques, while the problem of integrating stakeholder information into land use models has received little attention. Using the example of a land use model developed for the Guadiamar basin in South West Spain, location of the emblematic Doñana natural area, an integrated methodology for participatory calibration and evaluation of model results is presented which combines information from key stakeholders across a range of sectors with analytical model calibration techniques. Both discursive and analytical techniques are presented side by side to demonstrate that including participatory approaches is likely to improve both calibration results and model applicability. Integration of participatory methods into land use models is more likely to be successful if stakeholders are selected carefully so as to make best possible use of their time and knowledge, and are involved in the modelling process from the beginning of the project cycle.     

Handling effective communication to support awareness in rescue operations

Efficient rescue operations require a high level of situation awareness amongst decision‐makers and first responders for the purpose of achieving operations successfully and reducing losses. Moreover, a common operational picture between involved actors is required in order to support decision‐making. Therefore, different organisations and agencies have to collaborate, cooperate, and coordinate their actions with each other. Hence, effective interactions and communications between participants are vital to fulfil these essential needs. However, emergency actors still lack backing to exchange information effectively and ensure a common operational picture in order to reach shared situational awareness. For this reason, we aim to develop and implement Rescue MODES, a communication system oriented to support situation awareness amongst French emergency actors in rescue operations. In this paper, we examine and analyse actors’ activities and interactions, so that the system will be based on the real needs of actors. We start by studying and modelling the communications, interactions, and information flow. This modelling is based on an application ontology. Then, we define requirements for good communication in these operations and present some existing systems in France and how each system responds to these requirements.