Multiagent resource allocation in service networks

The term service network (SN) denotes a network of software services in which complex software applications are provided to customers by aggregating multiple elementary services. These networks are based on the service-oriented computing (SOC) paradigm, which defines the fundamental technical concepts for software services over electronic networks, e.g., Web services and, most recently, Cloud services. For the provision of software services to customers, software service providers (SPs) have to allocate their scarce computational resources (i.e., hardware and software) of a certain quality to customer requests. The SOC paradigm facilitates interoperability over organizational boundaries by representing business relationships on the software system level. Composite software services aggregate multiple software services into software applications. This aggregation is denoted as service composition. The loose coupling of services leads to SNs as dynamic entities with changing interdependencies between services. For composite software services, these dependencies exist across SN tiers; they result from the procurement of services, which are themselves utilized to produce additional services, and constitute a major problem for resource allocation in SNs. If these dependencies are not considered, the fulfillment of agreements may become unaccomplishable (overcommitment). Hence, the consideration of service dependencies is crucial for the allocation of service providers resources to fulfill customer requests in SNs. However, existing resource allocation methods, which could consider these dependencies -- such as combinatorial auctions with a central auctioneer for the whole SN -- are not applicable, since there are no central coordinating entities in SNs. The application of an allocation mechanism that does not consider these dependencies might negatively affect the actual service delivery; results are penalty payments as well as a damage to the reputation of the providers. This research is conducted in accordance to the design science paradigm in information system research. It is a problem-solving paradigm, which targets the construction and evaluation of IT artifacts. The objectives of this research are to develop and evaluate an allocation protocol, which can consider multi-tier service dependencies without the existence of central coordinating entities. Therefore, an interaction protocol engineering (IPE) perspective is applied to solve the problem of multi-tier dependencies in resource allocation. This approach provides a procedure model for designing interaction protocols for multiagent systems, and is closely related to the well-established area of communication protocol engineering. Automated resource allocation in SNs is analyzed in this research by representing the actors as autonomous software agents in the software system. The actors delegate their objectives to their software agents, which conduct the negotiations for service provision on their behalf. Thus, these agents communicate concerning the resource allocation; in this process, the sequence of communication interactions is crucial to the problem addressed. Interaction protocols define a structured exchange of defined messages between agents; they facilitate agent conversations. When multiple agents have to reach agreements by negotiation and bargaining, such as in case with allocating scarce resources, game theory provides means to formalize and analyze the most rational choice of actions for the interacting agents. Based on a formal framework for resource allocation in SNs, this research first performs a game-theoretic problem analysis; it is concerned with the existence, as well as the complexity of computing optimal allocations. In addition, Nash equilibria are analyzed for optimal allocations. Second, a distributed, auction-based allocation protocol, which prevents overcommitments and guarantees socially optimal allocations for single customer requests under certain assumptions, is proposed. Therefore, a game-theoretic model and an operationizable specification of the protocol are presented. Third, it is formally verified that the protocol enables multi-tier resource allocation and avoids overcommitments by proofs for the game-theoretic model and by model checking for the interaction protocol specification; using the model checker Spin, safety properties like the absence of deadlock are as well formally verified as the protocol enabling multi-tier resource allocation. Fourth, the efficacy and the benefits of the proposed protocol are demonstrated by multiagent simulation for concurrent customers. The experimental evaluation provides evidence of the protocols efficiency compared to the socially optimal allocation as a centralized benchmark in different settings, e.g., network topologies and different bidding policies.Der Begriff Service Network (SN) bezeichnet ein Netzwerk von Software-Services, in dem komplexe Software-Applikationen durch Aggregation mehrerer elementarer Services für Kunden bereitgestellt werden. Diese Netzwerke basieren auf dem Paradigma des Service-oriented Computing, welches die grundlegenden technischen Konzepte für Software-Services über elektronische Netzwerke bereitstellt, d.h. Web Services und zuletzt Cloud-Computing. Für die Bereitstellung von Software-Services für Kunden müssen Software-Anbieter ihre knappen Ressourcen (d.h. Hardware und Software) einer bestimmten Qualität zu Kundenanfragen allozieren, also entsprechende Ressourcen reservieren, um Software-Services in der vereinbarten Dienstgüte bereitzustellen. Zusammengesetzte Software-Services aggregieren mehrere Software-Services zu Software-Applikations-Services. Diese Aggregation wird als Service-Komposition bezeichnet. Die lose Kopplung von Services macht SNs zu dynamischen Entitäten mit sich verändernden Interdependenzen zwischen den Services. Für zusammengesetzte Software-Services existieren solche Abhängigkeiten über mehrere SN-Stufen; sie ergeben sich durch die Beschaffung von Services, welche für die Produktion von weiteren Services verwendet werden, und stellen ein Hauptproblem bei der Ressourcenallokation in SN dar. Werden diese Abhängigkeiten nicht berücksichtigt, kann die Erfüllung von Vereinbarungen undurchführbar werden (overcommitment). Daher ist die Berücksichtigung von Service-Abhängigkeiten bei der Allokation von Ressourcen der Service-Anbieter für die Erfüllung der Kundenanfragen in SNs entscheidend. Existierende Methoden der Ressourcenallokation, welche diese Abhängigkeiten berücksichtigen könnten -- wie kombinatorische Auktionen mit einem zentralen Auktionator für das gesamte SN -- sind jedoch nicht anwendbar, da in SNs keine zentralen Koordinationsentitäten existieren. Der Einsatz eines Allokationsmechanismus, welcher diese Abhängigkeiten nicht berücksichtigt, kann die konkrete Service-Erbringung negativ beeinflussen und somit in Strafzahlungen und einer Beeinträchtigung der Reputation der Service-Anbieter resultieren. Die vorliegende Forschungsarbeit wird in Übereinstimmung mit dem Design Science-Paradigma durchgeführt. Dabei handelt es sich um ein Problemlösungs-Paradigma, welches die Konstruktion und Evaluation von IT-Artefakten zum Ziel hat. Ziel dieser Forschungsarbeit ist die Entwicklung und Evaluation eines Allokationsprotokolls, welches mehrstufige Service-Abhängigkeiten ohne die Existenz zentraler, koordinierender Entitäten berücksichtigen kann. Zu diesem Zweck wird eine Interaction-Protocol-Engineering (IPE)-Perspektive eingenommen, um das Problem mehrstufiger Abhängigkeiten bei der Ressourcenallokation zu lösen. Dieser Ansatz stellt ein Vorgehensmodell für den Entwurf von Interaktionsprotokollen für Multiagentensysteme zur Verfügung. Diese Forschungsarbeit analysiert die automatisierte Ressourcenallokation in SNs durch die Repräsentation der Akteure als autonome Softwareagenten im Softwaresystem. Die Akteure delegieren ihre Ziele an ihre Softwareagenten, welche in deren Auftrag die Verhandlung für die Service-Erbringung durchführen. Somit kommunizieren diese Softwareagenten bezüglich der Ressourcenallokationen; dabei ist die Abfolge der Interaktionen für das adressierte Problem elementar. Interaktionsprotokolle definieren einen strukturierten Austausch bestimmter Nachrichten zwischen Agenten. Wenn mehrere Agenten Vereinbarungen durch Verhandlungen treffen müssen, wie im Falle der Allokation knapper Ressourcen, stellt die Spieltheorie Methoden bereit, um rationale Entscheidungen der Aktionen für interagierende Agenten zu analysieren. Basierend auf einem formalen Modell für Ressourcenallokation in SN führt diese Forschungsarbeit eine spieltheoretische Problemanalyse durch. Hierbei werden insbesondere mehrstufige Abhängigkeiten von Vereinbarungen berücksichtigt. Die Problemanalyse befaßt sich mit der Existenz sowie der Komplexität der Berechnung optimaler Allokationen. Es wird ein verteiltes, Auktions-basiertes Allokationsprotokoll, welches overcommitments vermeidet, vorgeschlagen. Basierend auf dem spieltheoretischen Modell wird gezeigt, daß das vorgeschlagene Protokoll overcommitments vermeidet und sozial optimale Allokationen für einzelne Kundenanfragen unter bestimmten Annahmen garantiert. Darüber hinaus wird der Modellprüfer Spin verwendet, um bestimmte formale Eigenschaften der Beschreibung des Protokolls zu beweisen. Abschließend werden die Anwendbarkeit und der Nutzen des vorgeschlagenen Protokolls mittels Multiagentensimulation demonstriert. In den Simulationsexperimenten wird die Effizienz des Protokolls mit der optimalen Allokation als zentralisiertes Benchmark in unterschiedlichen Einstellungen (z.B. Netzwerktopologien oder Anzahl von Kunden- und Anbieter-Agenten) für verschiedene Bietrichtlinien für Anbieter verglichen

Combinatorial Auction-based Mechanisms for Composite Web Service Selection

Composite service selection presents the opportunity for the rapid development of complex applications using existing web services. It refers to the problem of selecting a set of web services from a large pool of available candidates to logically compose them to achieve value-added composite services. The aim of service selection is to choose the best set of services based on the functional and non-functional (quality related) requirements of a composite service requester. The current service selection approaches mostly assume that web services are offered as single independent entities; there is no possibility for bundling. Moreover, the current research has mainly focused on solving the problem for a single composite service. There is a limited research to date on how the presence of multiple requests for composite services affects the performance of service selection approaches. Addressing these two aspects can significantly enhance the application of composite service selection approaches in the real-world. We develop new approaches for the composite web service selection problem by addressing both the bundling and multiple requests issues. In particular, we propose two mechanisms based on combinatorial auction models, where the provisioning of multiple services are auctioned simultaneously and service providers can bid to offer combinations of web services. We mapped these mechanisms to Integer Linear Programing models and conducted extensive simulations to evaluate them. The results of our experimentation show that bundling can lead to cost reductions compared to when services are offered independently. Moreover, the simultaneous consideration of a set of requests enhances the success rate of the mechanism in allocating services to requests. By considering all composite service requests at the same time, the mechanism achieves more homogenous prices which can be a determining factor for the service requester in choosing the best composite service selection mechanism to deploy

Uma proposta de arquitetura de resiliência computacional para infraestruturas baseadas em SOA de empresas virtuais

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia de Automação e Sistemas, Florianópolis, 2019Uma Empresa Virtual (EV) é um tipo de rede colaborativa de organizações na qual grupos de empresas se unem dinâmica, lógica e temporariamente para melhor atender a demandas de mercado. Atuando como se fossem uma única empresa, compartilham recursos, custos e riscos de um negócio, representando assim um proeminente modelo de sustentabilidade, especialmente para pequenas e médias empresas. Uma das pré-condições para atuar numa EV é que os sistemas computacionais dos seus membros interoperem para que os processos de negócio associados à EV possam ser executados sem problemas pelos mais diversos sistemas envolvidos. Esta tese explora um cenário onde todos os sistemas das empresas são implementados de uma forma que possam ser expostos como serviços de software numa perspectiva SOA (Service Oriented Architecture), serem invocados pelos processos de negócio da EV em questão e, ao mesmo tempo, possam ser compartilhados com os outros membros. Desta forma, quando uma EV é formada, um grande sistema distribuído baseado em serviços é dinamicamente criado. Dado que em uma EV novas empresas podem entrar e outras sair ao longo de sua existência, tal sistema não é estático, mas sim deve alterar sua composição, tanto em tempo de projeto, quanto em tempo de execução. Como cada empresa pode participar simultaneamente em mais do que uma EV, isso também significa que cada um dos seus serviços poderá estar envolvido ao mesmo tempo em inúmeras orquestrações, porém em diferentes contextos de negócio e requisitos de qualidade de serviço. Este sistema computacional (e seus inúmeros serviços) deve permanecer operacional ao longo de todo ciclo de vida da EV de forma a sustentar a execução dos processos e, assim, do negócio. Em um sistema como esse, largamente distribuído e com serviços implementados em diferentes tecnologias, várias falhas podem ocorrer. Esta tese propõe uma arquitetura computacional para um sistema de resiliência para esse cenário, fazendo com que o sistema como um todo se recupere diante das falhas e mantenha o nível de qualidade de serviço geral do negócio da EV. Após pesquisa na literatura, não foram encontrados trabalhos que cobrissem a área de intersecção entre resiliência, SOA e EV. Baseado no modelo de referência de computação autonômica MAPE-K, a arquitetura proposta é auto resiliente e foi concebida ela mesma como SOA; portanto distribuída, com baixo acoplamento e escalável. Além disso, seu projeto contempla as modernas visões de economia orientada a serviços, compreendendo ecossistemas de provedores de serviços de software. Para garantir a permanência da EV em operação, várias técnicas consolidadas de tolerância a falhas foram empregadas, combinadas e adaptadas ao cenário em questão, atuando tanto reativamente como proativamente, e respeitando os níveis de responsabilidade das camadas de negócio, TI e de infraestrutura computacional. Um robusto protótipo de software foi implementado como prova de conceito, onde se buscou utilizar o maior número possível de padrões abertos de TI. Ele foi avaliado experimentalmente em um cenário controlado de EV. Ao se aplicar indicadores de desempenho de referência, a arquitetura mostrou-se promissora, suportando a execução dos sistemas da EV na quase totalidade dos casos mesmo diante de inúmeras falhas. A implementação teve algumas simplificações e o desenho da arquitetura partiu de uma série de pressupostos. Ao final, conclusões finais do trabalho são apresentadas bem como um conjunto de trabalhos futuros é sugerido.Abstract: Virtual Enterprises (VE) is a type of collaborative networked organization in which groups of companies are dynamically, logically and temporally joined to better meet market demands. Acting as a single company, they share resources, costs and business risks, thus representing a prominent sustainability model, especially for small and medium-sized enterprises. One of the preconditions for operating as an EV is that the members? IT systems should interoperate in way the business processes associated with EV can be executed by the most diverse involved systems without problems. This thesis exploits a scenario where all company systems are implemented in way they can be exposed as software services in the SOA (Service Oriented Architecture) perspective, being invoked by the VE?s business processes and, at the same time, can be shared with the other members. In this way, when an EV is formed, a large distributed service-based system is dynamically created. Given that new companies can enter and other leave a VE during the general VE process, such system is not static, but rather can change its composition, both at design and run time. Yet, since given companies can participate in many EV simultaneously, this also means that their services can be involved in diverse orchestrations although in different business contexts and quality of services requirements. This computational system (and its many services) should remain operating throughout the VE?s life cycle in order to sustain the execution of the processes and thus of the business. In a system like this, widely distributed and with services implemented in different technologies, several failures can occur. This thesis proposes a resilience system computing architecture for this scenario, making the system able to recover from failures while maintaining the level of general service quality of the VE business. After a literature research, no works were found out that covered the intersection area of resilience, SOA and VE. Based on the MAPE-K autonomic computing reference model, the proposed architecture is self-resilient and was conceived as a SOA itself; therefore, it is distributed, loosely coupled and scalable. In addition, its design adopts the modern vision of service-oriented economy, comprising ecosystems of software service providers. In order to guarantee the VE operation, several fault tolerance techniques were used, combined and adapted to that scenario, acting both reactively and pro-actively, and respecting the responsibility levels of the business, IT and computing infrastructure layers. A robust software prototype was implemented as proof of concept, using as many open IT standards as possible. It was evaluated experimentally in a controlled VE scenario. After the application of reference performance indicators, the architecture showed to be promising, supporting the VE?s systems execution in almost all cases in the presence of numerous failures. The implementation has simplifications and the architecture design has adopted several assumptions. Conclusions are presented in the end, including suggestions for future work

Multi-Agent Systems

This Special Issue ""Multi-Agent Systems"" gathers original research articles reporting results on the steadily growing area of agent-oriented computing and multi-agent systems technologies. After more than 20 years of academic research on multi-agent systems (MASs), in fact, agent-oriented models and technologies have been promoted as the most suitable candidates for the design and development of distributed and intelligent applications in complex and dynamic environments. With respect to both their quality and range, the papers in this Special Issue already represent a meaningful sample of the most recent advancements in the field of agent-oriented models and technologies. In particular, the 17 contributions cover agent-based modeling and simulation, situated multi-agent systems, socio-technical multi-agent systems, and semantic technologies applied to multi-agent systems. In fact, it is surprising to witness how such a limited portion of MAS research already highlights the most relevant usage of agent-based models and technologies, as well as their most appreciated characteristics. We are thus confident that the readers of Applied Sciences will be able to appreciate the growing role that MASs will play in the design and development of the next generation of complex intelligent systems. This Special Issue has been converted into a yearly series, for which a new call for papers is already available at the Applied Sciences journal’s website: https://www.mdpi.com/journal/applsci/special_issues/Multi-Agent_Systems_2019

Special section on autonomic cloud computing: Technologies, services, and applications

The November 2011 special issue of Concurrency and Computation: Practice and Experience offers papers from autonomic cloud computing: technologies, services, and applications. Richter and co-researchers propose an algorithm for the decomposition of global utility boundary into atomic service utility boundaries, and the surplus redistribution from successful negotiation outcomes among the remaining negotiations in their paper titled 'Establishing Composite SLAs through Concurrent QoS Negotiation with Surplus Redistribution'. In the paper titled 'A data dependency based strategy for intermediate data storage in scientific cloud workflow systems', Yuan et al. build an intermediate data dependency graph (IDG) from the data provenance in scientific workflows. In the paper titled 'Towards autonomic management for Cloud services based upon volunteered resources', Caton and Rana propose a methodology that addresses the issues of unreliability and unpredictability such that Cloud software services could be hosted upon volunteered resources

Bioinspired metaheuristic algorithms for global optimization

This paper presents concise comparison study of newly developed bioinspired algorithms for global optimization problems. Three different metaheuristic techniques, namely Accelerated Particle Swarm Optimization (APSO), Firefly Algorithm (FA), and Grey Wolf Optimizer (GWO) are investigated and implemented in Matlab environment. These methods are compared on four unimodal and multimodal nonlinear functions in order to find global optimum values. Computational results indicate that GWO outperforms other intelligent techniques, and that all aforementioned algorithms can be successfully used for optimization of continuous functions

Experimental Evaluation of Growing and Pruning Hyper Basis Function Neural Networks Trained with Extended Information Filter

In this paper we test Extended Information Filter (EIF) for sequential training of Hyper Basis Function Neural Networks with growing and pruning ability (HBF-GP). The HBF neuron allows different scaling of input dimensions to provide better generalization property when dealing with complex nonlinear problems in engineering practice. The main intuition behind HBF is in generalization of Gaussian type of neuron that applies Mahalanobis-like distance as a distance metrics between input training sample and prototype vector. We exploit concept of neuron’s significance and allow growing and pruning of HBF neurons during sequential learning process. From engineer’s perspective, EIF is attractive for training of neural networks because it allows a designer to have scarce initial knowledge of the system/problem. Extensive experimental study shows that HBF neural network trained with EIF achieves same prediction error and compactness of network topology when compared to EKF, but without the need to know initial state uncertainty, which is its main advantage over EKF

Safety and Reliability - Safe Societies in a Changing World

The contributions cover a wide range of methodologies and application areas for safety and reliability that contribute to safe societies in a changing world. These methodologies and applications include: - foundations of risk and reliability assessment and management - mathematical methods in reliability and safety - risk assessment - risk management - system reliability - uncertainty analysis - digitalization and big data - prognostics and system health management - occupational safety - accident and incident modeling - maintenance modeling and applications - simulation for safety and reliability analysis - dynamic risk and barrier management - organizational factors and safety culture - human factors and human reliability - resilience engineering - structural reliability - natural hazards - security - economic analysis in risk managemen