Combining reliability, reputation and honesty to enhance QoS on Federated Computing Infrastructures Antonello Comi * , Lidia Fotia * * DIIES, University of Reggio Calabria, Italy, {comi,lidia.fotia}@unirc.it Abstract—In this paper, we suggest an approach aimed at maximising the “global utility” (i.e., QoS) perceived into a large-scale federated computing infrastructures. Our approach computes the node and starts a procedure for the formation of coalitions between them. In particular, it is based on a trust model that allows actors to quantify the trustworthiness of their peers, and on a decentralised procedure that allows the Computing Federation to optimise the QoS. We define the generic SLA- based federated architecture, that is the global QoS offered by the federation, and we describe the theoretical foundation on which our proposal is based. Finally, we illustrate the experimental results which prove that the Global Capital of the Computing Federation improves. Index Terms—Cloud federation, Multi-agent System, Grid Federations, Trust, Group Formation. I. I NTRODUCTION In the last few years, the increasing complexity of grid tasks has brought a remarkable change in the grid infrastructure. In particular, the grid computing paradigm has evolved from the Virtual Organisations (VO) to the federated grid architectures, in which grid brokers and grid institutions share resources among different grid infrastructures thus resulting in a more flexible approach. Indeed, as grid clients send requests composed by complex requirements, they will relay on the collaboration between grid VOs, which are able to provide specialised resources to the result of the expected computation. Therefore, the main objective is represented by the need of achieving high efficiency in allocating federated resources. This scenario produces competition among computing nodes, which want to improve performances provided to their clients [1]–[7]. At the same time, it implies the presence of possible malicious behaviours, because the service providers promise performances that will not be actually realised. Based on the considerations above, a trust model [3], [8]–[10] can assist clients and grid nodes to quantify the expected level of performance and mutual trust. In the literature, past proposals present strategies for re- source allocation, without to consider trust issues. For this reasons, we present a trust-based approach aiming at max- imising the QoS perceived within the grid federation. Our solution is based on the use of software agents [11] that manage every node which may be a grid computing element, a grid site, a part of a cloud centre. We focus on two concepts: the resource sets that is the sets of computational resources characterising complex requirements in federated computing infrastructures, and the agent aggregation that allows collaboration between federated nodes. In particular, we propose an algorithm for agent Friendship and Group Formation (FGF) to maximise the “global utility” also said Global Capital, of the whole federation. This trust model combines some measures of reliability and reputation to obtain a unique synthetic trust measure. The plan of the paper is as follows. In Section II, we survey the related work of the recent literature Section III describe the software agent used for the formation of nodes. Section IV introduces the trust model, while in Section V we propose the FGF algorithm for forming friendships and groups. Section VI shows a few experiments to prove the effectiveness of our approach. Finally, in Section VII, we draw our conclusions. II. RELATED WORK In this section, we survey the literature related to the issue of partner/node selection in the context of self-interested agents and grid systems and focus on the principal metrics proposed to deal with the the problem addressed in this work. Various types of evaluation metrics were proposed to select appropriate partners, for example by exploiting local decision and models [12]–[16] or by promoting agent interactions to realise a distributed social control mechanism for evaluating other agents or their provided services [17], [18]. Many of such models are based on direct observations and/or on communications with other agents. Moreover, they consider different criteria as trust, reputation, provided QoS, etc. In this context, the concept of belief can be considered as a situational awareness, and its modification can require to select the most appropriate providers for information. To achieve this aim, the authors suggest the use of social control [19] as a way to create secure open systems. Them idea is to let the agents in the system be responsible for the security of the system but without having a global authority. In the information exchange domain, research on belief revision also involves how to select appropriate informa- tion providers. Belief is, in general, a situational awareness, and research investigating belief revision in multi-agent sys- tems [20]–[23] pursues a similar objective: build the agents’ beliefs accurately and efficiently by using all the information provided. In these approaches, the beliefs are assigned pref- erences by epistemic relevance in a symbolic logic [20], or 45