Apostolos Malatras

Enabling efficient information discovery in a self-structured grid

One of the key success factors enabling the deployment of large scale grid systems is the existence of efficient resource discovery mechanisms. Accordingly, the main issues to be addressed by such a grid information system are those of scalability and minimal network overhead. In this respect, we propose a solution based on proactive information caching supported by a self-structured overlay topology. The proposed approach features a fully distributed ant-inspired self-organized overlay construction that maintains a bounded diameter overlay, and a selective flooding-based discovery algorithm that exploits local caches to reduce the number of visited nodes. To improve the caching scheme while retaining minimal bandwidth consumption, cache contents are periodically exchanged between neighboring nodes using an epidemic replication mechanism that is based on a gossiping algorithm, thus allowing nodes to have a more general view of the network and its resources. Extensive experimentation provides evidence that the average number of hops required to efficiently locate resources is limited and that our framework performs well with respect to hit rate and network overhead.

NoizCrowd: A Crowd-Based Data Gathering and Management System for Noise Level Data

Many systems require access to very large amounts of data to properly function, like systems allowing to visualize or predict meteorological changes in a country over a given period of time, or any other system holding, processing and displaying scientific or sensor data. However, filling out a database with large amounts of valuable data can be a difficult, costly and time-consuming task. In this paper, we present techniques to create large amounts of data by combining crowdsourcing, data generation models, mobile computing, and big data analytics. We have implemented our methods in a system, NoizCrowd, allowing to crowdsource noise levels in a given region and to generate noise models by using state-of-the-art noise propagation models and array data management techniques. The resulting models and data can then be accessed using a visual interface.

Proactive information caching for efficient resource discovery in a self-structured grid

The cornerstone of successful deployment of large scale grid systems depends on efficient resource discovery mechanisms. In this respect, this paper presents a grid information system supported by a self-structured overlay topology and proactive information caching. The proposed approach features an ant-inspired self-organized overlay construction that maintains a bounded diameter overlay, and a selective flooding based discovery algorithm that exploit local caches to reduce the number of visited nodes. The caches are periodically exchanged between neighboring nodes using an epidemic replication mechanism that is based on a gossiping algorithm, thus allowing nodes to have a more general view of the network and its resources. We conducted extensive experimentation that provides evidence that the average number of hops required to efficiently locate resources is limited and that our framework performs well with respect to hit rate and network overhead.

AntOM: Constructing multi-layer overlays for pervasive environments

Pervasive environments are becoming increasingly more popular due to the benefits of context-aware, user-centric service provisioning, despite their inherent challenges, i.e. dynamicity, heterogeneity and complexity. In such environments, multiple applications with distinct network requirements run simultaneously over the same underlying networks. Serving as abstractions to the latter, P2P overlays enable applications to operate over virtual networks that adhere to specified requirements. In this respect, we propose here AntOM, a topology optimisation algorithm for multi-layer P2P overlays on top of pervasive environments. The algorithm is inspired by Ant Colony Optimisation in regards to the network exploration and neighborhood optimisation. By utilising different ant families, multiple overlay layers, each one optimised for a different property, can be concurrently maintained at a low cost as proven by our experimental results. Therefore, applications with diverse requirements can be served at the same time by exploiting the same network infrastructure.

A self-management framework for efficient resource discovery in pervasive environments

When considering resource discovery in pervasive environments, issues such as the diversity of application requirements, different classes of Quality of Service (QoS), device and network heterogeneity should be addressed. In these cases, static solutions prove to be ineffective since the desired characteristics of resource discovery mechanisms are constantly changing. To alleviate such problems, a promising direction involves self-management approaches that allow for adaptation of the monitoring mechanisms and their automatic reconfiguration. Accordingly, we present our ongoing work on a context-aware, policy-based framework to support the autonomic management of pervasive environments monitoring mechanisms that rely on dynamic, bio-inspired P2P overlays.

ARiA: A Protocol for Dynamic Fully Distributed Grid Meta-scheduling

Critical to the successful deployment of grid systems is their ability to guarantee efficient meta-scheduling, namely optimal allocation of jobs across a pool of sites with diverse local scheduling policies. The centralized nature of current meta-scheduling solutions is not well suited for the envisioned increasing scale and dynamicity of next-generation grids, the success of which relies on the development of fully distributed, flexible and autonomic systems tailored to very large sets of highly volatile and heterogeneous resources. In this respect, we introduce a fully distributed grid meta-scheduling scheme that effectively addresses the concerns regarding the scalability and adaptability of future grid systems. Our approach employs a lightweight protocol, called A RiA, that is based on peer-to-peer communication between grid nodes, and makes use of dynamic rescheduling to consider and adapt to changes in the availability of resources. Extensive evaluation by means of an in depth simulation study highlighted the effectiveness of the proposed solution in improving the overall performance in terms of job completion time and load-balancing.

FLEXIBLE RULES: A Player Oriented Board Game Development Framework

When comparing digital board games with theirtraditional counterparts, it becomes clear that certain featuressuch as graphics, mundane task automation or saving andrestoring the state of the game have been greatly improved.Nonetheless, the transition to a digital environment leads toa loss of the flexibility that makes traditional board gamesinherently popular. While modifying aspects of the game isstraightforward in traditional board games, achieving sucha level of customization in the digital domain requires deepknowledge of and access to the game source code. In thispaper we focus on board games and by means of an in-depthonline survey we validate our previous observation, namelythat enhancements should be made to digital board games byincorporating gaming facets found in the physical environment,e.g. support for flexibility by means of house rules. To this end,we introduce a conceptual model for the design of digital boardgames, which is supported by a set of visual programmingtools to enable game development according to the principlesset out by our proposed model. The set of the tools along withthe underlying intuitive model comprise the FLEXIBLERULESframework, which enables and facilitates flexible and extensiblegame design and development.

Decoupling Aspects in Board Game Modeling

Existing research on computer enhanced board games is mainly focused on user interaction issues and look-and-feel, however, this overlooks the flexibility of traditional board games when it comes to game rule handling. In this respect, the authors argue that successful game designs need to exploit the advantages of the digital world as well as retaining such flexibility. To achieve this goal, both the rules of the game and the graphical representation should be simple to define at the design stage, and easy to change before or even during a game session. For that reason, the authors propose a framework allowing the implementation of all aspects of a board game in a fully flexible and decoupled way. This paper will describe the Flexiblerules approach, which combines both a model driven and an aspect oriented design of computer enhanced board games. The benefits of this approach are discussed and illustrated in the case of three different board games.

A Context-Aware Framework to Enable Adaptation in Pervasive Computing Environments

Pervasive computing environments based on the ubiquitous communications paradigm have attracted significant research interest and have found increased applicability in commercial settings, attributed to the fact that they provide seamless, customized and unobtrusive services to their users. The majority of solutions proposed in the related literature to enable pervasive computing involves specific platforms and rigid architectures that are tightly bound with their target applications and services. This approach suffers from having to introduce new context-aware applications, thus limiting deployment in existing configurations. Nevertheless, the notion of pervasive computing calls for solutions to be tailored to user needs and not conversely. In this paper we introduce a framework that enables systems to become pervasive in a transparent manner, handling context monitoring and ubiquitous communications issues behind the scenes without affecting existing applications. Pervasive behavior is guaranteed by adapting systems based on monitored context information and guiding their re-configuration. We present the architecture of our proposed framework and discuss application scenarios, while considering evaluation aspects.

A framework for the autonomic management of multi-layer P2P overlays

The advent of pervasive environments and the future Internet has brought on heterogeneity, large scale and dynamicity in current networking infrastructures, which nonetheless also promote flexibility, availability, adaptability and support for mobility. With the increasing diversity in the users networking requirements, solutions based on network virtualization techniques such as P2P overlays emerge as promising approaches to create network infrastructures with desirable characteristics. Successful deployment of such P2P overlays necessitates however efficient management mechanisms. Taking into account that static solutions are not geared towards handling the dynamics of the considered environments, as well as the diversity of users and applications requirements, adaptive solutions become prominent. We present here the design of an autonomic framework to concurrently manage multiple P2P overlays built on top of pervasive environments, by utilising context information and high-level policies to guide their reconfiguration. Relevant organizational requirements and design issues are also highlighted.