Web Intelligence and Agent Systems: An International Journal - Volume 11, issue 1

Authors: Chou, Bin-Hui | Suzuki, Einoshin

Article Type: Research Article

Abstract: Graph clustering, or community detection, is an important task of discovering the underlying structure in a network by clustering vertices in a graph into communities. In the past decades, non-overlapping methods such as normalized cuts and modularity-based methods, which assume that each vertex belongs to a single community, are proposed to discover disjoint communities. On the other hand, overlapping methods such as CPM, which assume that each vertex can belong to multiple communities, have been drawing increasing attention as the assumption fits the reality. In this paper, we show that existing non-overlapping and overlapping methods lack consideration to edges that …link a vertex to its neighbors belonging to different communities, which often leads to counter-intuitive results of vertices located near borders of communities. Therefore, we propose a new graph clustering methods named RoClust, which uses three roles, bridges, gateways and hubs to discover communities. Each of the three roles represents a kind of vertices that connect communities. Experimental results show that RoClust outperforms state-of-the-art methods of graph clustering including non-overlapping and overlapping methods. Show more

Keywords: Graph clustering, community detection, overlapping communities, role, social network analysis

DOI: 10.3233/WIA-130259

Citation: Web Intelligence and Agent Systems: An International Journal, vol. 11, no. 1, pp. 1-20, 2013

Authors: Hoogendoorn, Mark | Jaffry, Syed Waqar | van Maanen, Peter-Paul | Treur, Jan

Article Type: Research Article

Abstract: Within human trust related behaviour, according to the literature from the domains of Psychology and Social Sciences often non-rational behaviour can be observed. Current trust models that have been developed typically do not incorporate non-rational elements in the trust formation dynamics. In order to enable agents that interact with humans to have a good estimation of human trust, and take this into account in their behaviour, trust models that incorporate such human aspects are a necessity. A specific non-rational element in humans is that they are often biased in their behaviour. In this paper, models for human trust dynamics are …presented incorporating human biases. In order to show that they more accurately describe human behaviour, they have been evaluated against empirical data, which shows that the models perform significantly better. Show more

Keywords: Trust, biases, modelling, validation

DOI: 10.3233/WIA-130260

Citation: Web Intelligence and Agent Systems: An International Journal, vol. 11, no. 1, pp. 21-40, 2013

Authors: Bollen, Dirk | Halpin, Harry

Article Type: Research Article

Abstract: Most tagging systems support the user in the tag selection process by providing tag suggestions, or recommendations, based on a popularity measurement of tags other users provided when tagging the same resource, such as web-page. In this paper we investigate the influence of tag suggestions on the emergence of power-law distributions as a result of collaborative tag behavior. Although previous research has already shown that power-laws emerge in tagging systems, the cause of why power-law distributions emerge is not understood empirically. The majority of theories and mathematical models of tagging found in the literature assume that the emergence of power-laws …in tagging systems is mainly driven by the imitation behavior of users when observing tag suggestions provided by the user interface of the tagging system. This imitation behavior leads to a feedback loop in which some tags are reinforced, which is also known as the ‘rich get richer’ or a preferential attachment model. We present experimental results showing that the power-law distribution forms when tag suggestions are not presented to the users, and the power-law distribution does not hold when tag suggestions are presented to the user. Furthermore, we show that the real effect of tag suggestions is rather subtle; the power-law distribution that would naturally occur without tag suggestions is ‘compressed’ if tag suggestions are given to the user, resulting in a shorter long tail and a ‘compressed’ top of the power-law distribution. We show that tag suggestions by themselves do not account for the formation of power-law distributions in tagging systems. Show more

Keywords: Distributed information systems, information retrieval, user interfaces

DOI: 10.3233/WIA-130261

Citation: Web Intelligence and Agent Systems: An International Journal, vol. 11, no. 1, pp. 41-53, 2013

Authors: Zhang, Zhongyi | Liu, Yanbin | Li, Jiguang | Yang, Bo | Yu, Fanhua | Liu, Dayou

Article Type: Research Article

Abstract: The real-world continuous double auction (CDA) market is a dynamic environment. However, most of the existing agent bidding strategies are simply designed for static markets. A new detecting method for bidding strategy is necessary for more practical simulations and applications. In this paper, we present a novel agent-based computing approach called the GDX Plus (GDXP) model. In the proposed model, trades are decided according to the market events in history combined with the forecast of market trends. The GDXP model employs a dynamic adjustment mechanism to make the bidding strategy adapt to the shocks in a dynamic environment. The experimental …results of the comparison between GDXP and other typical models, with respect to both static and dynamic CDA markets, demonstrate the performance of the GDXP model. Show more

Keywords: Agents, agent-based computational economics, bidding strategy, CDA

DOI: 10.3233/WIA-130262

Citation: Web Intelligence and Agent Systems: An International Journal, vol. 11, no. 1, pp. 55-65, 2013

Authors: Karrels, Daniel R. | Peterson, Gilbert L. | Mullins, Barry E.

Article Type: Research Article

Abstract: Large-scale systems are part of a growing trend in distributed computing, and coordinating control of them is an increasing challenge. This paper presents a cooperative agent system that scales to one million or more nodes in which agents form coalitions to complete global task objectives. This approach uses the large-scale Command and Control (C2) capabilities of the Resource Clustered Chord (RC-Chord) Hierarchical Peer-to-Peer (HP2P) design. Tasks are submitted that require access to processing, data, or hardware resources, and a distributed agent search is performed to recruit agents to satisfy the distributed task. This approach differs from others by incorporating design …elements to accommodate large-scale systems into the resource location algorithm. Peersim simulations demonstrate that the distributed coalition formation algorithm is as effective as an omnipotent central algorithm in a one million agent system. Show more

Keywords: Distributed multi-agent system, hierarchical peer to peer, large-scale, command and control

DOI: 10.3233/WIA-130263

Citation: Web Intelligence and Agent Systems: An International Journal, vol. 11, no. 1, pp. 67-79, 2013

Authors: Cheng, Shanjun | Raja, Anita | Lesser, Victor

Article Type: Research Article

Abstract: It is crucial for embedded systems to adapt to the dynamics of open environments. This adaptation process becomes especially challenging in the context of multiagent systems. In this paper, we argue that multiagent meta-level control is an effective way to determine when this adaptation process should be done and how much effort should be invested in adaptation as opposed to continuing with the current action plan. We use a reinforcement learning based local optimization algorithm within each agent to learn multiagent meta-level control agent policies in a decentralized fashion. These policies will allow each agent to adapt to changes in …environmental conditions while reorganizing the underlying multiagent network when needed. We then augment the agent with a heuristic rule-based algorithm that uses information provided by the reinforcement learning algorithm in order to resolve conflicts among agent policies from a local perspective at both learning and execution stages. We evaluate this mechanism in the context of a multiagent tornado tracking application called NetRads. Empirical results show that adaptive multiagent meta-level control significantly improves the performance of the tornado tracking network for a variety of weather scenarios. Show more

Keywords: Multiagent systems, meta-level control, dec-mdps, multiagent reinforcement learning, conflict resolution

DOI: 10.3233/WIA-130264

Citation: Web Intelligence and Agent Systems: An International Journal, vol. 11, no. 1, pp. 81-105, 2013