Author name cluster

Samhar Mahmoud

Possible papers associated with this exact author name in Arrow. This page groups case-insensitive exact name matches and is not a full identity disambiguation profile.

7 papers

2 author rows

KER Journal 2017 Journal Article

Engineering the emergence of norms: a review

Chris Haynes
Michael Luck
Peter McBurney
Samhar Mahmoud
Tomáš Vítek
Simon Miles

Abstract Complex systems often exhibit emergent behaviour, unexpected macro-level behaviour caused by the interaction of micro-level components. In multiagent systems, these micro-level components may be autonomous agents and the emergent behaviour may be expressed as norms—patterns of behaviour that arise among the agents in response to their environment and each other. These emergent norms may be beneficial (e.g. by encouraging cooperative behaviour), or detrimental, but in either case it is useful to recognize these norms as they emerge and either encourage or discourage their establishment. We term this process engineering the emergence of norms and have identified three steps: the identification of a possible norm, evaluation of its benefit and its encouragement (or discouragement). This paper is an attempt to provide a survey of existing research related to these steps. We also provide an analysis of the approaches based upon their suitability for a variety of normative systems: we examine the requirements for agents to have autonomy over their choice of norms, the degree of observability required in the system, and the norm enforcement methods. The paper concludes with an discussion of open issues.

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JAAMAS Journal 2017 Journal Article

Establishing norms with metanorms over interaction topologies

Samhar Mahmoud
Nathan Griffiths
Michael Luck

Abstract Norms are a valuable means of establishing coherent cooperative behaviour in decentralised systems in which there is no central authority. Axelrod’s seminal model of norm establishment in populations of self-interested individuals provides some insight into the mechanisms needed to support this through the use of metanorms, but considers only limited scenarios and domains. While further developments of Axelrod’s model have addressed some of the limitations, there is still only limited consideration of such metanorm models with more realistic topological configurations. In response, this paper tries to address such limitation by considering its application to different topological structures. Our results suggest that norm establishment is achievable in lattices and small worlds, while such establishment is not achievable in scale-free networks, due to the problematic effects of hubs. The paper offers a solution, first by adjusting the model to more appropriately reflect the characteristics of the problem, and second by offering a new dynamic policy adaptation approach to learning the right behaviour. Experimental results demonstrate that this dynamic policy adaptation overcomes the difficulties posed by the asymmetric distribution of links in scale-free networks, leading to an absence of norm violation, and instead to norm emergence.

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AAMAS Conference 2016 Conference Paper

Cooperation Emergence under Resource-Constrained Peer Punishment

Samhar Mahmoud
Simon Miles
Michael Luck

In distributed computational systems with no central authority, social norms have shown great potential in regulating the behaviour of self-interested agents, due to their distributed cost. In this context, peer punishment has been an important instrument in enabling social norms to emerge, and such punishment is usually assigned a certain enforcement cost that is paid by agents applying it. However, models that investigate the use of punishment as a mechanism to allow social norms to emerge usually assume that unlimited resources are available to agents to cope with the resulting enforcement costs, yet this assumption may not hold in real world computational systems, since resources are typically limited and thus need to be used optimally. In this paper, we use a modified version of the metanorm model originally proposed by Axelrod [1] to investigate this, and show that it allows norm emergence only in limited cases under bounded resources. In response, we propose a resource-aware adaptive punishment technique to address this limitation, and give an experimental evaluation of the new technique that shows it enables norm establishment under limited resources.

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AAMAS Conference 2016 Conference Paper

Reputation-based Provider Incentivisation for Provenance Provision (Extended Abstract)

Lina Barakat
Samhar Mahmoud
Phillip Taylor
Nathan Griffiths
Simon Miles

Knowledge of circumstances under which past service provisions have occurred enables clients to make more informed selection decisions regarding their future interaction partners. Service providers, however, may often be reluctant to release such circumstances due to the cost and effort required, or to protect their interests. In response, we introduce a reputation-based incentivisation framework, which motivates providers towards the desired behaviour of reporting circumstances via influencing two reputation-related factors: the weights of past provider interactions, which directly impact the provider’s reputation estimate, and the overall confidence in such estimates.

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AILAW Journal 2015 Journal Article

Establishing norms with metanorms in distributed computational systems

Samhar Mahmoud
Nathan Griffiths
Jeroen Keppens
Adel Taweel
Trevor J. M. Bench-Capon
Michael Luck

Abstract Norms provide a valuable mechanism for establishing coherent cooperative behaviour in decentralised systems in which there is no central authority. One of the most influential formulations of norm emergence was proposed by Axelrod (Am Political Sci Rev 80(4): 1095–1111, 1986 ). This paper provides an empirical analysis of aspects of Axelrod’s approach, by exploring some of the key assumptions made in previous evaluations of the model. We explore the dynamics of norm emergence and the occurrence of norm collapse when applying the model over extended durations. It is this phenomenon of norm collapse that can motivate the emergence of a central authority to enforce laws and so preserve the norms, rather than relying on individuals to punish defection. Our findings identify characteristics that significantly influence norm establishment using Axelrod’s formulation, but are likely to be of importance for norm establishment more generally. Moreover, Axelrod’s model suffers from significant limitations in assuming that private strategies of individuals are available to others, and that agents are omniscient in being aware of all norm violations and punishments. Because this is an unreasonable expectation, the approach does not lend itself to modelling real-world systems such as online networks or electronic markets. In response, the paper proposes alternatives to Axelrod’s model, by replacing the evolutionary approach, enabling agents to learn, and by restricting the metapunishment of agents to cases where the original defection is observed, in order to be able to apply the model to real-world domains. This work can also help explain the formation of a “social contract” to legitimate enforcement by a central authority.

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ECAI Conference 2014 Conference Paper

Information-based Incentivisation when Rewards are Inadequate

Samhar Mahmoud
Lina Barakat
Simon Miles
Adel Taweel
Brendan Delaney
Michael Luck

In many cases, intermediaries play a major role in linking between service providers and their target users. Yet, attracting intermediaries at a marketplace to promote a service to their existing customers can be very challenging, since they are usually very busy and would incur additional cost as a result of such promotion. In response, this paper presents an information-based incentivisation framework, which combines financial rewards with other motivating information, in order to incentivise intermediaries at a marketplace to undertake service promotion. Specifically, the intermediaries are associated with a group of incentivising agents, capable of learning the individual motivational needs of these intermediaries, and accordingly target them with the most effective incentives. The incentivising agents collaborate with each other to gather motivational information, by sharing their observations on intermediaries. The proposed incentivisation approach is evaluated through a corresponding agent-based simulation, and the experimental results obtained demonstrate its effectiveness.

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ECAI Conference 2012 Conference Paper

Efficient Norm Emergence through Experiential Dynamic Punishment

Samhar Mahmoud
Nathan Griffiths
Jeroen Keppens
Michael Luck

Peer punishment has been an effective means to ensure that norms are complied with in a population of self-interested agents. However, current approaches to establishing norms have only considered static punishments, which do not vary with the magnitude or frequency of norm violation. Such static punishments are difficult to apply because it is difficult to identify an appropriate fixed penalty: one that is not too weak to disincentivise norm violations and not too strong to lead to significant deleterious effects on the system as a whole (such as those incurred by losing the benefits of a member of the population). This paper addresses this concern by developing an adaptive punishment technique that tailors penalty to norm violation. An experimental evaluation of the approach demonstrates its value compared to static punishment. In particular, the results show that our dynamic punishment technique is capable of achieving norm emergence, even when starting with an amount of punishment that is too low to achieve emergence in the traditional static approach.

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