Corrado Santoro

A Trust-Based Approach for a Competitive Cloud/Grid Computing Scenario

Cloud/Grid systems are composed of nodes that individually manage local resources, and when a client request is submitted to the system, it is necessary to find the most suitable nodes to satisfy that request. In a competitive scenario, each node is in competition with each other to obtain the assignment of available tasks. In such a situation, it is possible that a node, in order to obtain the assignment of a task, can lie when declaring its own capability. Therefore, lying nodes will need to require the collaboration of other nodes to complete the task and consequently the problem arises of finding the most promising collaborators. In such a context, to make effective this selection, each node should have a trust model for accurately choosing its interlocutors. In this paper, a trust-based approach is proposed to make a node capable of finding the most reliable interlocutors. This approach, in order to avoid the exploration of the whole node space, exploits a P2P resource finding approach for clouds/grids, capable of determining the admissible region of nodes to be considered for the search of the interlocutors.

ComplexSim: a flexible simulation platform for complex systems

This paper describes ComplexSim, a C-based simulation platform intended to support the study of P2P systems and complex networks. Its architecture is based on two layers: 1) the parallel simulation kernel, which manages the execution of simulations on SMP systems, by providing a clean API enabling the definition and scheduling of tasks and events; 2) the complex network data and runtime, which allows a complex network to be defined as a graph of entities endowed with user-defined attributes and runtime behaviour. This paper describes the design of ComplexSim as well as the API it provides. Moreover, some experimental results are reported, showing that, even in the case of huge complex networks with hundred million nodes, ComplexSim exhibits better performances, in terms of memory consumption and processing times, with respect to similar solutions.

HySoN: A Distributed Agent-Based Protocol for Group Formation in Online Social Networks

On-line social networks allow people to easily interact with each other by means of social computer services. This scenario makes possible to search in a social network for affinities or new opportunities that satisfy specific requirements. However, for many users such activities often imply undesirable accesses to personal sensitive data. In this scenario we propose a novel approach, called HySoN (Hyperspace Social Network), based on an overlay network of software agents. HySoN allows users to locally maintain sensitive user’s data, satisfying the privacy requirements preserving sensitive data. Indeed, the properties involved in the HySoN user aggregation are inferred by local data not published in the social network. Some experimental results obtained on simulated on-line social networks data show the searching of suitable nodes is very efficient due to the topology of the overlay network, which exhibits the small-world properties.

ComplexSim: An SMP-Aware Complex Network Simulation Framework

This paper describes Complex Sim, a C-based simulation framework aiming at providing a simple and powerful support to the study of complex networks and P2P protocols evolution by means of simulations on symmetric multiprocessing (SMP) systems. The lower architectural layer of complex Sim, the Parallel Simulation Kernel, includes a complete support for multi-threading which allows to gain a speedup when running simulations on SMP systems. The Parallel Simulation Kernel allows to define and schedule (parallel) tasks and events with a simple API, without dealing with the management of threads, which are hidden by the simulation kernel itself. The Complex Network Data & Runtime is the architectural upper layer. It allows to define a complex network or P2P system model as a graph of entities with user-defined attributes and runtime behavior. By means of the API of Complex Sim, the user code is able to simulate the evolution of its own model by focusing only on the run-time behavior of the network and the nodes, without necessary dealing with aspects such as graph management, message exchange between nodes, event management, task/thread scheduling.

An Agent Based Negotiation Protocol for Cloud Service Level Agreements

In an agent-based cloud scenario, when two agents, provided with different ontologies exchange messages to negotiate a Service Level Agreement for a cloud service, they could fail to understand both the correct meaning of their messages and the offered service quality, due to the differences present in their ontologies. In all these cases, a semantic negotiation is required to reciprocally making understandable the messages exchanged about the cloud service characteristics. In this work we propose a protocol for supporting the SLA negotiation process, involving semantic issues, which do not require the use of a common global agent ontology sharing knowledge in advance. In detail, this protocol considers that each agent is able to partition the other agents based on both their expertise in cloud services and similarity with their own ontologies.

A Distributed Agent-Based Approach for Supporting Group Formation in P2P e-Learning

Peer-to-Peer (P2P) technology can be effectively used to implement cooperative e-Learning systems, where the available knowledge for a student is not only from teachers, but also from other students having similar interests and preferences. In such a scenario, a central issue is to form groups of users having similar interests and satisfying personal users constraints. In this paper we propose a novel approach, called HADEL (Hyperspace Agent-based E-Learning), based on an overlay network of software agents. Our approach preserves users privacy, allowing to locally maintain sensitive users data and inferring the properties necessary for determining the groups by using agents acting as personal assistants. The results obtained by some tests performed on simulated e-Learning environments show the efficiency of our approach, that suitably exploits the topology of the overlay network, which exhibits the typical properties of a small-world system.

An economic model for resource management in a Grid-based content distribution network

This paper presents an architecture to federate Content Distribution Networks (CDNs) in order to share computational resources, thus building an infrastructure that we call a Content Distribution Grid (CDG). The purpose of a CDG is to use a community policy allowing each CDN to put together a portion of its own resources to meet each others requirements, and therefore to guarantee a stronger quality of service to users. Since CDNs of a CDG belong to different organisations, the interaction scenario can be considered competitive, that is, organizations are mainly self-interested and are aiming at maximizing the performances of its own system. For this reason, the resource sharing policy proposed here is based on a offer/demand competitive model, in which resources are purchased by paying for them a certain amount of (virtual or real) money. An economic model is thus derived to guide such a sale; here the CDN requesting resources (buyer) and the CDN offering resources (seller) agree on the quantity and the price by means of a utility-based negotiation approach. A multi-agent system is then proposed to realise the software architecture supporting this model of CDG.

Design Patterns for RTSJ Application Development

The Real-Time Specification for Java provides a memory model, based on memory areas, which introduces some constraints on objects allocation and references. For this reason, many well-known design patterns cannot be used in a RTSJ environment since their structure violates such constraints. In this context, this paper proposes some new RTSJ design patterns and idioms, as well as a re-interpretation of existing patterns into a RTSJ perspective. Five patterns are presented. Three of them are an adaptation to RTSJ world of well-known design patterns—the singleton, the abstract factory and the leader-follower. The other two are new patterns—the eager exception handler and the memory tunnel—which allow to solve some peculiar problems deriving from the constraints of RTSJ memory model.

Integrating Cloud Services in Behaviour Programming for Autonomous Robots

This paper introduces CLEPTA, an extension to the PROFETA robotic programming framework for the integration of cloud services in developing the software for autonomous robots. CLEPTA provides a set of basic classes, together with a software architecture, which helps the programmer in specifying the invocation of cloud services in the programs handling robots behaviour; such a feature allows designers (i) to execute computation-intensive algorithms and (ii) to include, in robots behaviour, additional features made available in the Cloud.

Exploiting the Small-World Effect for Resource Finding in P2P Grids/Clouds

This paper presents a resource finding and allocation scheme for Grid-/Cloud-computing systems, called SWHYGRA (Small-World HYperspace-based Grid Resource Allocation). It models the overall system using a decentralized peer-to-peer approach organizing the nodes in an overlay network featuring specific convenient properties. SWHYGRA intends to exploit the small-world effect, by employing an algorithm aimed at building an overlay network whose structure mimics the small-world model. Such networks feature a high clustering degree coupled with a very low average path length, both being key characteristics for the SW-HYGRA approach. The former allows nodes with similar resource availability to be clustered; together with the latter, it permits a resource finding algorithm to reach a target node in a fast and efficient way.