Systems composed of interacting autonomous agents offer a promising software engineering approach for developing applications in complex domains. However, this multiagent system paradigm introduces a number of new abstractions and design/development issues when compared with more traditional approaches to software development. Accordingly, new analysis and design methodologies, as well as new tools, are needed to effectively engineer such systems. Against this background, the contribution of this article is twofold. First, we synthesize and clarify the key abstractions of agent-based computing as they pertain to agent-oriented software engineering. In particular, we argue that a multiagent system can naturally be viewed and architected as a computational organization, and we identify the appropriate organizational abstractions that are central to the analysis and design of such systems. Second, we detail and extend the Gaia methodology for the analysis and design of multiagent systems. Gaia exploits the aforementioned organizational abstractions to provide clear guidelines for the analysis and design of complex and open software systems. Two representative case studies are introduced to exemplify Gaia's concepts and to show its use and effectiveness in different types of multiagent system.

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Developing multiagent systems: The Gaia methodology

The Internet of Things (IoT) envisages a future in which digital and physical things or objects (e.g., smartphones, TVs, cars) can be connected by means of suitable information and communication technologies, to enable a range of applications and services. The IoT’s characteristics, including an ultra-large-scale network of things, device and network level heterogeneity, and large numbers of events generated spontaneously by these things, will make development of the diverse applications and services a very challenging task. In general, middleware can ease a development process by integrating heterogeneous computing and communications devices, and supporting interoperability within the diverse applications and services. Recently, there have been a number of proposals for IoT middleware. These proposals mostly addressed wireless sensor networks (WSNs), a key component of IoT, but do not consider RF identification (RFID), machine-to-machine (M2M) communications, and supervisory control and data acquisition (SCADA), other three core elements in the IoT vision. In this paper, we outline a set of requirements for IoT middleware, and present a comprehensive review of the existing middleware solutions against those requirements. In addition, open research issues, challenges, and future research directions are highlighted.

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Middleware for Internet of Things: A Survey

Autonomic communications seek to improve the ability of network and services to cope with unpredicted change, including changes in topology, load, task, the physical and logical characteristics of the networks that can be accessed, and so forth. Broad-ranging autonomic solutions require designers to account for a range of end-to-end issues affecting programming models, network and contextual modeling and reasoning, decentralised algorithms, trust acquisition and maintenance---issues whose solutions may draw on approaches and results from a surprisingly broad range of disciplines. We survey the current state of autonomic communications research and identify significant emerging trends and techniques.

A survey of autonomic communications

A blockchain is a distributed ledger for recording transactions, maintained by many nodes without central authority through a distributed cryptographic protocol. All nodes validate the information to be appended to the blockchain, and a consensus protocol ensures that the nodes agree on a unique order in which entries are appended. Consensus protocols for tolerating Byzantine faults have received renewed attention because they also address blockchain systems. This work discusses the process of assessing and gaining confidence in the resilience of a consensus protocols exposed to faults and adversarial nodes. We advocate to follow the established practice in cryptography and computer security, relying on public reviews, detailed models, and formal proofs; the designers of several practical systems appear to be unaware of this. Moreover, we review the consensus protocols in some prominent permissioned blockchain platforms with respect to their fault models and resilience against attacks. The protocol comparison covers Hyperledger Fabric, Tendermint, Symbiont, R3~Corda, Iroha, Kadena, Chain, Quorum, MultiChain, Sawtooth Lake, Ripple, Stellar, and IOTA.

Blockchain Consensus Protocols in the Wild

We consider heuristic algorithms for the resource-constrained project scheduling problem. Starting with a literature survey, we summarize the basic components of heuristic approaches. We briefly describe so-called X -pass methods which are based on priority rules as well as metaheuristic algorithms. Subsequently, we present the results of our in-depth computational study. Here, we evaluate the performance of several state-of-the-art heuristics from the literature on the basis of a standard set of test instances and point out to the most promising procedures. Moreover, we analyze the behavior of the heuristics with respect to their components such as priority rules and metaheuristic strategy. Finally, we examine the impact of problem characteristics such as project size and resource scarceness on the performance.

Experimental evaluation of state-of-the-art heuristics for the resource-constrained project scheduling problem

Recent peer-to-peer (P2P) systems are characterized by decentralized control, large scale and extreme dynamism of their operating environment. As such, they can be seen as instances of complex adaptive systems (CAS) typically found in biological and social sciences. We describe Anthill, a framework to support the design, implementation and evaluation of P2P applications based on ideas such as multi-agent and evolutionary programming borrowed from CAS. An Anthill system consists of a dynamic network of peer nodes; societies of adaptive agents travel through this network, interacting with nodes and cooperating with other agents in order to solve complex problems. Anthill can be used to construct different classes of P2P services that exhibit resilience, adaptation and self-organization properties. We also describe preliminary experiences with Anthill in implementing a file sharing application.

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Anthill: a framework for the development of agent-based peer-to-peer systems

Peer-to-peer (P2P) systems are characterized by decentralized control, large-scale and extreme dynamism of their environment. Developing applications that can cope with these characteristics requires a paradigm shift that puts adaptation, resilience and self-organization as primary concerns. Complex adaptive systems (CAS), commonly used to explain the behavior of many biological and social systems, could be an appropriate response to these requirements. In order to pursue these ideas, this paper presents Messor, a decentralized load-balancing algorithm based on techniques such as multi-agent systems drawn from CAS. A novel P2P grid computing system has been designed using the Messor algorithm, allowing arbitrary users to initiate computational tasks.

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Messor: load-balancing through a swarm of autonomous agents

In this paper, we describe the design and implementation of BChain, a Byzantine fault-tolerant state machine replication protocol, which performs comparably to other modern protocols in fault-free cases, but in the face of failures can also quickly recover its steady state performance. Building on chain replication, BChain achieves high throughput and low latency under high client load. At the core of BChain is an efficient Byzantine failure detection mechanism called re-chaining, where faulty replicas are placed out of harm’s way at the end of the chain, until they can be replaced. Our experimental evaluation confirms our performance expectations for both fault-free and failure scenarios. We also use BChain to implement an NFS service, and show that its performance overhead, with and without failures, is low, both compared to unreplicated NFS and other BFT implementations.

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BChain: Byzantine Replication with High Throughput and Embedded Reconfiguration

This paper presents the design and implementation of Jgroup-ARM, a distributed object group platform with autonomous replication management along with a novel measurement-based assessment technique that is used to validate the fault-handling capability of Jgroup-ARM. Jgroup extends Java RMI through the group communication paradigm and has been designed specifically for application support in partitionable systems. ARM aims at improving the dependability characteristics of systems through a fault-treatment mechanism. Hence, ARM focuses on deployment and operational aspects, where the gain in terms of improved dependability is likely to be the greatest. The main objective of ARM is to localize failures and to reconfigure the system according to application-specific dependability requirements. Combining Jgroup and ARM can significantly reduce the effort necessary for developing, deploying and managing dependable, partition-aware applications. Jgroup-ARM is evaluated experimentally to validate its fault-handling capability; the recovery performance of a system deployed in a wide area network is evaluated. In this experiment multiple nearly coincident reachability changes are injected to emulate network partitions separating the service replicas. The results show that Jgroup-ARM is able to recover applications to their initial state in several realistic failure scenarios, including multiple, concurrent network partitionings. Copyright © 2007 John Wiley & Sons, Ltd.

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Jgroup-ARM: a distributed object group platform with autonomous replication management

This paper presents the design and implementation of a simple and elegant middleware architecture providing virtual sensors as representatives for any type of physical sensors. With our middleware, clients can seamlessly discover sensor-hosted services through Zeroconf and it provides a standardized communication interface that applications can use without having to deal with sensor-specific details. The limited capabilities of most types of sensors prevent the inclusion of a full communication stack with IP addressing. Yet, through the use of virtual sensors, a uniform communication interface based on UDP/TCP sockets can be exposed to clients. This will significantly simplify application development for integrated services involving multiple types of sensors. Our benchmarks shows that our middleware scales well beyond the requirements of a private smart home.

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Hein Meling

Papers

Anthill: a framework for the development of agent-based peer-to-peer systems

Messor: load-balancing through a swarm of autonomous agents

BChain: Byzantine Replication with High Throughput and Embedded Reconfiguration

Jgroup-ARM: a distributed object group platform with autonomous replication management

SenseWrap: A service oriented middleware with sensor virtualization and self-configuration