Is a Semantic Web Agent a Knowledge-Savvy Agent?

The issue of knowledge sharing has permeated the field of distributed AI and in particular, its successor, multiagent systems. Through the years, many research and engineering efforts have tackled the problem of encoding and sharing knowledge without the need for a single, centralized knowledge base. However, the emergence of modern computing paradigms such as distributed, open systems have highlighted the importance of sharing distributed and heterogeneous knowledge at a larger scale—possibly at the scale of the Internet. The very characteristics that define the Semantic Web—that is, dynamic, distributed, incomplete, and uncertain knowledge—suggest the need for autonomy in distributed software systems. Semantic Web research promises more than mere management of ontologies and data through the definition of machine-understandable languages. The openness and decentralization introduced by multiagent systems and service-oriented architectures give rise to new knowledge management models, for which we can’t make a priori assumptions about the type of interaction an agent or a service may be engaged in, and likewise about the message protocols and vocabulary used. We therefore discuss the problem of knowledge management for open multi-agent systems, and highlight a number of challenges relating to the exchange and evolution of knowledge in open environments, which pertinent to both the Semantic Web and Multi Agent System communities alike

Graffiti Networks: A Subversive, Internet-Scale File Sharing Model

The proliferation of peer-to-peer (P2P) file sharing protocols is due to their efficient and scalable methods for data dissemination to numerous users. But many of these networks have no provisions to provide users with long term access to files after the initial interest has diminished, nor are they able to guarantee protection for users from malicious clients that wish to implicate them in incriminating activities. As such, users may turn to supplementary measures for storing and transferring data in P2P systems. We present a new file sharing paradigm, called a Graffiti Network, which allows peers to harness the potentially unlimited storage of the Internet as a third-party intermediary. Our key contributions in this paper are (1) an overview of a distributed system based on this new threat model and (2) a measurement of its viability through a one-year deployment study using a popular web-publishing platform. The results of this experiment motivate a discussion about the challenges of mitigating this type of file sharing in a hostile network environment and how web site operators can protect their resources

Data-link alternatives for the NASA pilot data systems

There are several preliminary, or pilot, efforts for developing data systems for supporting NASA science research. The Pilot Data Systems consist of the Pilot Land Data System (PLDS), the Pilot Ocean Data System (PODS), the Pilot Climate Data System (PCDS), and the Pilot Planetary Data System (PPDS). The PLDS is likely to have the greatest communication needs of the various pilots. Communications issues and requirements are examined in the context of the mature PLDS as it may exist by 1990. The PLDS is seen as a distributed processing system linking resources at a number of NASA research centers and outside universities. Large image data sets, including LANDSAT scenes, are a major data type to be moved along the PLDS communications network. The unusually large size of these data files requires examining new technologies that may allow efficient and affordable communication at rates of up to 60 megabits per second. Potentially useful developments include portable satellite ground stations, and time division multiple access for sharing high-speed satellite links. Further pooling of communications for the various data systems into a single network would reduce costs and may make economic justification of access to the required data rates possible

Resource Sharing via Capability-Based Multiparty Session Types

Multiparty Session Types (MPST) are a type formalism used to model communication protocols among components in distributed systems, by specifying type and direction of data transmitted. It is standard for multiparty session type systems to use access control based on linear or affine types. While useful in offering strong guarantees of communication safety and session fidelity, linearity and affinity run into the well-known problem of inflexible programming, excluding scenarios that make use of shared channels or need to store channels in shared data structures. In this paper, we develop capability-based resource sharing for multiparty session types. In this setting, channels are split into two entities, the channel itself and the capability of using it. This gives rise to a more flexible session type system, which allows channel references to be shared and stored in persistent data structures. We illustrate our type system through a producer-consumer case study. Finally, we prove that the resulting language satisfies type safety

A Distributed Ledger based infrastructure for Intelligent Transportation Systems

Intelligent Transportation Systems (ITS) are proposed as an efficient way to improve performances in transportation systems applying information, communication, and sensor technologies to vehicles and transportation infrastructures. The great amount of vehicles produced data, indeed, can potentially lead to a revolution in ITS development, making them more powerful multifunctional systems. To this purpose, the use of Vehicular Ad-hoc Networks (VANETs) can provide comfort and security to drivers through reliable communications. Meanwhile, distributed ledgers have emerged in recent years radically evolving the way that we used to consider finance, trust in communication and even renewing the concept of data sharing and allowing to establish autonomous, secured, trusted and decentralized systems. In this work an ITS infrastructure based on the combination of different emerging Distributed Ledger Technologies (DLTs) and VANETs is proposed, resulting in a transparent, self-managed and self-regulated system, that is not fully managed by a central authority. The intended design is focused on the user ability to use any type of DLT-based application and to transact using Smart Contracts, but also on the access control and verification over user’s vehicle produced data. Users "smart" transactions are achieved thanks to the Ethereum blockchain, widely used for distributed trusted computation, whilst data sharing and data access is possible thanks to the use of IOTA, a DLT fully designed to operate in the Internet of Things landscape, and IPFS, a protocol and a network that allows to work in a distributed file system. The aim of this thesis is to create a ready-to-work infrastructure based on the hypothesis that every user in the ITS must be able to participate. To evaluate the proposal, an infrastructure implementation is used in different real world use cases, common in Smart Cities and related to the ITS, and performance measurements are carried out for DLTs used

On Distributed Storage Codes

Distributed storage systems are studied. The interest in such system has become relatively wide due to the increasing amount of information needed to be stored in data centers or different kinds of cloud systems. There are many kinds of solutions for storing the information into distributed devices regarding the needs of the system designer. This thesis studies the questions of designing such storage systems and also fundamental limits of such systems. Namely, the subjects of interest of this thesis include heterogeneous distributed storage systems, distributed storage systems with the exact repair property, and locally repairable codes. For distributed storage systems with either functional or exact repair, capacity results are proved. In the case of locally repairable codes, the minimum distance is studied. Constructions for exact-repairing codes between minimum bandwidth regeneration (MBR) and minimum storage regeneration (MSR) points are given. These codes exceed the time-sharing line of the extremal points in many cases. Other properties of exact-regenerating codes are also studied. For the heterogeneous setup, the main result is that the capacity of such systems is always smaller than or equal to the capacity of a homogeneous system with symmetric repair with average node size and average repair bandwidth. A randomized construction for a locally repairable code with good minimum distance is given. It is shown that a random linear code of certain natural type has a good minimum distance with high probability. Other properties of locally repairable codes are also studied.Siirretty Doriast

Long-Term Confidential Secret Sharing-Based Distributed Storage Systems

Secret sharing-based distributed storage systems can provide long-term protection of confidentiality and integrity of stored data. This is achieved by periodically refreshing the stored shares and by checking the validity of the generated shares through additional audit data. However, in most real-life environments (e.g. companies), this type of solution is not optimal for three main reasons. Firstly, the access rules of state of the art secret sharing-based distributed storage systems do not match the hierarchical organization in place in these environments. Secondly, data owners are not supported in selecting the most suitable storage servers while first setting up the system nor in maintaining it secure in the long term. Thirdly, state of the art approaches require computationally demanding and unpractical and expensive building blocks that do not scale well. In this thesis, we mitigate the above mentioned issues and contribute to the transition from theory to more practical secret sharing-based long-term secure distributed storage systems. Firstly, we show that distributed storage systems can be based on hierarchical secret sharing schemes by providing efficient and secure algorithms, whose access rules can be adapted to the hierarchical organization of a company and its future modifications. Secondly, we introduce a decision support system that helps data owners to set up and maintain a distributed storage system. More precisely, on the one hand, we support data owners in selecting the storage servers making up the distributed storage system. We do this by providing them with scores that reflect their actual performances, here used in a broad sense and not tied to a specific metric. These are the output of a novel performance scoring mechanism based on the behavioral model of rational agents as opposed to the classical good/bad model. On the other hand, we support data owners in choosing the right secret sharing scheme parameters given the performance figures of the storage servers and guide them in updating them accordingly with the updated performance figures so as to maintain the system secure in the long term. Thirdly, we introduce efficient and affordable distributed storage systems based on a trusted execution environment that correctly outsources the data and periodically computes valid shares. This way, less information-theoretically secure channels have to be established for confidentiality guarantees and more efficient primitives are used for the integrity safeguard of the data. We present a third-party privacy-preserving mechanism that protects the integrity of data by checking the validity of the shares