Multihop data delivery through vehicular ad hoc networks is complicated by the fact that vehicular networks are highly mobile and frequently disconnected. To address this issue, we adopt the idea of carry and forward, where a moving vehicle carries a packet until a new vehicle moves into its vicinity and forwards the packet. Being different from existing carry and forward solutions, we make use of predictable vehicle mobility, which is limited by traffic pattern and road layout. Based on the existing traffic pattern, a vehicle can find the next road to forward the packet to reduce the delay. We propose several vehicle-assisted data delivery (VADD) protocols to forward the packet to the best road with the lowest data-delivery delay. Experimental results show that the proposed VADD protocols outperform existing solutions in terms of packet-delivery ratio, data packet delay, and protocol overhead. Among the proposed VADD protocols, the hybrid probe (H-VADD) protocol has a much better performance.

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VADD: Vehicle-Assisted Data Delivery in Vehicular Ad Hoc Networks

A super-peer is a node in a peer-to-peer network that operates both as a server to a set of clients, and as an equal in a network of super-peers. Super-peer networks strike a balance between the efficiency of centralized search, and the autonomy, load balancing and robustness to attacks provided by distributed search. Furthermore, they take advantage of the heterogeneity of capabilities (e.g., bandwidth, processing power) across peers, which recent studies have shown to be enormous. Hence, new and old P2P systems like KaZaA and Gnutella are adopting super-peers in their design. Despite their growing popularity, the behavior of super-peer networks is not well understood. For example, what are the potential drawbacks of super-peer networks? How can super-peers be made more reliable? How many clients should a super-peer take on to maximize efficiency? we examine super-peer networks in detail, gaming an understanding of their fundamental characteristics and performance tradeoffs. We also present practical guidelines and a general procedure for the design of an efficient super-peer network.

Designing an Super-Peer Network

In our work we extend the traditional bipartite model of ontologies with the social dimension, leading to a tripartite model of actors, concepts and instances We demonstrate the application of this representation by showing how community-based semantics emerges from this model through a process of graph transformation We illustrate ontology emergence by two case studies, an analysis of a large scale folksonomy system and a novel method for the extraction of community-based ontologies from Web pages

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Ontologies are us: a unified model of social networks and semantics

In information systems, most research on knowledge management assumes that knowledge has positive implications for organizations. However, knowledge is a double-edged sword: while too little might result in expensive mistakes, too much might result in unwanted accountability. The purpose of this paper is to highlight the lack of attention paid to the unintended consequences of managing organizational knowledge and thereby to broaden the scope of IS-based knowledge management research. To this end, this paper analyzes the IS literature on knowledge management. Using a framework developed by Deetz (1996), research articles published between 1990 and 2000 in six IS journals are classified into one of four scientific discourses. These discourses are the normative, the interpretive, the critical, and the dialogic. For each of these discourses, we identify the research focus, the metaphors of knowledge, the theoretical foundations, and the implications apparent in the articles representing it. The metaphors of knowledge that emerge from this analysis are knowledge as object, asset, mind, commodity, and discipline. Furthermore, we present a paper that is exemplary of each discourse. Our objective with this analysis is to raise IS researchers' awareness of the potential and the implications of the different discourses in the study of knowledge and knowledge management.

Studying knowledge management in information systems research: discourses and theoretical assumptions

Multihop data delivery through vehicular ad hoc networks is complicated by the fact that vehicular networks are highly mobile and frequently disconnected. To address this issue, we adopt the idea of carry and forward, where a moving vehicle carries a packet until a new vehicle moves into its vicinity and forwards the packet. Being different from existing carry and forward solutions, we make use of predictable vehicle mobility, which is limited by traffic pattern and road layout. Based on the existing traffic pattern, a vehicle can find the next road to forward the packet to reduce the delay. We propose several vehicle-assisted data delivery (VADD) protocols to forward the packet to the best road with the lowest data-delivery delay. Experimental results show that the proposed VADD protocols outperform existing so- lutions in terms of packet-delivery ratio, data packet delay, and protocol overhead. Among the proposed VADD protocols, the Hybrid Probe (H-VADD) protocol has a much better performance.

/pdf/vadd-vehicle-assisted-data-delivery-in-vehicular-ad-hoc-4s0sz4r5ha.pdf

Internet, Web and distributed computing infrastructures continue to gain in popularity as a means of communication for organizations, groups and individuals alike. In such an environment, characterized by large distributed, autonomous, diverse, and dynamic information sources, access to relevant and accurate information is becoming increasingly complex. This complexity is exacerbated by the evolving system, semantic and structural heterogeneity of these potentially global, cross-disciplinary, multicultural and rich-media technologies. Clearly, solutions to these challenges require addressing directly a variety of interoperability issues.

Semantic interoperability in global information systems

In this paper we examine resource discovery in inter-vehicle ad-hoc networks in an urban area, where moving vehicles communicate with each other via short-range wireless transmission. Our focus is on real-time location-specific information. We explore an opportunistic approach to resource recovery, in which a vehicle obtains information about resources from encountered vehicles. The vehicle uses a spatio-temporal relevance function to sort the resources, and save only the most relevant ones. Our theoretical and experimental analysis indicates that the opportunistic exchange algorithm automatically limits the distribution of a resource to a bounded spatial area and to the duration for which the resource is of interest.

/pdf/opportunistic-resource-exchange-in-inter-vehicle-ad-hoc-3840064mda.pdf

Opportunistic resource exchange in inter-vehicle ad-hoc networks

Information and communication infrastructures underwent a rapid and extreme decentralization process over the past decade: From a world of statically and partially connected central servers rose an intricate web of millions of information sources loosely connecting one to another. Today, we expect to witness the extension of this revolution with the wide adoption of meta-data standards like RDF or OWL underpinning the creation of a semantic web. Again, we hope for global properties to emerge from a multiplicity of pair-wise, local interactions, resulting eventually in a self-stabilizing semantic infrastructure. This paper represents an effort to summarize the conditions under which this revolution would take place as well as an attempt to underline its main properties, limitations and possible applications.

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Emergent Semantics Principles and Issues

Increasingly companies are doing business in an environment replete with heterogeneous information systems which must cooperate. Cooperation between these systems presupposes the resolution of the semantic conflicts that are bound to occur. In this article, we propose a classification of semantic conflicts which can be used as the basis for the incremental discovery and resolution of these conflicts. We classify conflicts along the two dimensions of naming and abstraction which, taken together, capture the semantic mapping of the conflict. We add a third dimension, level of heterogeneity to assist in the schematic mapping between two databases. The classification provides a systematic representation of alternative semantic interpretations of conflicts during the reconciliation process. As a result, the design of query‐directed dynamic reconciliation systems is possible. The classification is shown to be sound and minimal. Completeness is discussed.

Aris M. Ouksel

Papers

Semantic interoperability in global information systems

Opportunistic resource exchange in inter-vehicle ad-hoc networks

Emergent Semantics Principles and Issues

A classification of semantic conflicts in heterogeneous database systems

Semantic Interoperability in Global Information Systems: A Brief Introduction to the Research Area a