On the Intrinsic Locality Properties of Web Reference Streams

There has been considerable work done in the study of Web reference streams: sequences of requests for Web objects. In particular, many studies have looked at the locality properties of such streams, because of the impact of locality on the design and performance of caching and prefetching systems. However, a general framework for understanding why reference streams exhibit given locality properties has not yet emerged. In this work we take a first step in this direction, based on viewing the Web as a set of reference streams that are transformed by Web components (clients, servers, and intermediaries). We propose a graph-based framework for describing this collection of streams and components. We identify three basic stream transformations that occur at nodes of the graph: aggregation, disaggregation and filtering, and we show how these transformations can be used to abstract the effects of different Web components on their associated reference streams. This view allows a structured approach to the analysis of why reference streams show given properties at different points in the Web. Applying this approach to the study of locality requires good metrics for locality. These metrics must meet three criteria: 1) they must accurately capture temporal locality; 2) they must be independent of trace artifacts such as trace length; and 3) they must not involve manual procedures or model-based assumptions. We describe two metrics meeting these criteria that each capture a different kind of temporal locality in reference streams. The popularity component of temporal locality is captured by entropy, while the correlation component is captured by interreference coefficient of variation. We argue that these metrics are more natural and more useful than previously proposed metrics for temporal locality. We use this framework to analyze a diverse set of Web reference traces. We find that this framework can shed light on how and why locality properties vary across different locations in the Web topology. For example, we find that filtering and aggregation have opposing effects on the popularity component of the temporal locality, which helps to explain why multilevel caching can be effective in the Web. Furthermore, we find that all transformations tend to diminish the correlation component of temporal locality, which has implications for the utility of different cache replacement policies at different points in the Web.National Science Foundation (ANI-9986397, ANI-0095988); CNPq-Brazi

Active caching for recommender systems

Web users are often overwhelmed by the amount of information available while carrying out browsing and searching tasks. Recommender systems substantially reduce the information overload by suggesting a list of similar documents that users might find interesting. However, generating these ranked lists requires an enormous amount of resources that often results in access latency. Caching frequently accessed data has been a useful technique for reducing stress on limited resources and improving response time. Traditional passive caching techniques, where the focus is on answering queries based on temporal locality or popularity, achieve a very limited performance gain. In this dissertation, we are proposing an ‘active caching’ technique for recommender systems as an extension of the caching model. In this approach estimation is used to generate an answer for queries whose results are not explicitly cached, where the estimation makes use of the partial order lists cached for related queries. By answering non-cached queries along with cached queries, the active caching system acts as a form of query processor and offers substantial improvement over traditional caching methodologies. Test results for several data sets and recommendation techniques show substantial improvement in the cache hit rate, byte hit rate and CPU costs, while achieving reasonable recall rates. To ameliorate the performance of proposed active caching solution, a shared neighbor similarity measure is introduced which improves the recall rates by eliminating the dependence on monotinicity in the partial order lists. Finally, a greedy balancing cache selection policy is also proposed to select most appropriate data objects for the cache that help to improve the cache hit rate and recall further

Emerging Informatics

The book on emerging informatics brings together the new concepts and applications that will help define and outline problem solving methods and features in designing business and human systems. It covers international aspects of information systems design in which many relevant technologies are introduced for the welfare of human and business systems. This initiative can be viewed as an emergent area of informatics that helps better conceptualise and design new world-class solutions. The book provides four flexible sections that accommodate total of fourteen chapters. The section specifies learning contexts in emerging fields. Each chapter presents a clear basis through the problem conception and its applicable technological solutions. I hope this will help further exploration of knowledge in the informatics discipline

A personalized system for scalable distribution of multimedia content in multicast wireless networks

The final publication is available at Springer via http://dx.doi.org/10.1007/s11042-014-2139-3This paper presents a novel architecture for scalable multimedia content delivery over wireless networks. The architecture takes into account both the user preferences and context in order to provide personalized contents to each user. In this way, third-party applications filter the most appropriate contents for each client in each situation. One of the key characteristics of the proposal is the scalability, which is provided, apart from the use of filtering techniques, through the transmission in multicast networks. In this sense, content delivery is carried out by means of the FLUTE (File Delivery over Unidirectional Transport) protocol, which provides reliability in unidirectional environments through different mechanisms such as AL-FEC (Application Layer Forward Error Correction) codes, used in this paper. Another key characteristic is the context-awareness and personalization of content delivery, which is provided by means of context information, user profiles, and adaptation. The system proposed is validated through several empirical studies. Specifically, the paper presents evaluations of two types that collect objective and subjective measures. The first evaluate the efficiency of the transmission protocol, analyzing how the use of appropriate transmission parameters reduces the download time (and thus increasing the Quality of Experience), which can be minimized by using caching techniques. On the other hand, the subjective measures present a study about the user experience after testing the application and analyze the accuracy of the filtering process/strategy. Results show that using AL-FEC mechanisms produces download times until four times lower than when no protection is used. Also, results prove that there is a code rate that minimizes the download time depending on the losses and that, in general, code rates 0.7 and 0.9 provide good download times for a wide range of losses. On the other hand, subjective measures indicate a high user satisfaction (more than 80 %) and a relevant degree of accuracy of the content adaption.This work is supported in part by the Ministerio de Economia y Competitividad of the Government of Spain under project COMINN (IPT-2012-0883-430000) and by the project PAID/2012/313 from the PAID-05-12 program of the Vicerrectorado de Investigacion of the Universitat Politecnica de Valencia.De Fez Lava, I.; Gil Pascual, M.; Fons Cors, JJ.; Guerri Cebollada, JC.; Pelechano Ferragud, V. (2014). A personalized system for scalable distribution of multimedia content in multicast wireless networks. 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Proc. of the OZCHI Computer-human interaction, Canberra, Australia:1–10Chen YFR, Jana R, Stern D, Wei B, Yang M, Sun H, Dyaberi J (2010) Zebroid: using IPTV data to support STB-assisted VoD content delivery. Multimedia System Journal 16(3):199–214Chen G, Kotz D (2000) A survey on context-aware mobile computing research. Technical Report TR2000-381, Dartmouth Computer ScienceCommunity Research and Development Information Service (CORDIS) – Seventh Framework Programme (FP7). Available at: http://cordis.europa.eu/fp7/home_en.html . Accesed October 2013de Fez I, Fraile F, Belda R, Guerri JC (2011) Performance evaluation of AL-FEC LDPC codes for push content applications in wireless unidirectional environments. Multimedia Tools and Applications 60(3):669–688de Fez I, Fraile F, Belda R, Guerri JC (2012) Analysis and evaluation of adaptive LDPC AL-FEC codes for content download services. IEEE Transactions on Multimedia 14(3):641–650de Fez I, Fraile F, Guerri JC (2013) Effect of the FDT transmission frequency for an optimum content delivery using the FLUTE protocol. Computer Communications 36(12):1298–1309de Fez I, Guerri JC (2014) An adaptive mechanism for optimal content download in wireless networks. IEEE Transactions on Multimedia 16(4):1140–1155Du R, Safavi-Naini R, Susilo W (2003) Web filtering using text classification (2003). 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Pricing and Resource Allocation in Caching Services With Multiple Levels of Quality of Service

Network caches are the storage centers in the supply chain for content delivery—the digital equivalent of warehouses. Operated by access networks and other operators, they provide benefits to content publishers in the forms of bandwidth cost reduction, response time improvement, and handling of flash crowds. Yet, caching has not been fully embraced by publishers, because its use can interfere with site personalization strategies and/or collection of visitor information for business intelligence purposes. While recent work has focused on technological solutions to these issues, this paper provides the first study of the managerial issues related to the design and provisioning of incentive-compatible caching services. Starting with a single class of caching service, we find conditions under which the profit-maximizing cache operator should offer the service for free. This occurs when the access networks’ bandwidth costs are high and a large fraction of content publishers value personalization and business intelligence. Some publishers will still opt out of the service, i.e., cache bust, as observed in practice. We next derive the conditions under which the profit-maximizing cache operator should provision two vertically differentiated service classes, namely, premium and best effort. Interestingly, caching service differentiation is different from traditional vertical differentiation models, in that the premium and best-effort market segments do not abut. Thus, optimal prices for the two service classes can be set independently and cannibalization does not occur. It is possible for the cache operator to continue to offer the best-effort service for free while charging for the premium service. Furthermore, consumers are better off because more content is cached and delivered faster to them. Finally, we find that declining bandwidth costs will put negative pressure on cache operator profits, unless consumer adoption of broadband connectivity and the availability of multimedia content provide the necessary increase in traffic volume for the caches

Future Transportation

Greenhouse gas (GHG) emissions associated with transportation activities account for approximately 20 percent of all carbon dioxide (co2) emissions globally, making the transportation sector a major contributor to the current global warming. This book focuses on the latest advances in technologies aiming at the sustainable future transportation of people and goods. A reduction in burning fossil fuel and technological transitions are the main approaches toward sustainable future transportation. Particular attention is given to automobile technological transitions, bike sharing systems, supply chain digitalization, and transport performance monitoring and optimization, among others

Leadership and innovation lessons from professional services firms

This paper compares and contrasts higher education with professional services firms. It considers what (if anything) leaders in higher education may gain from reflecting on how other sectors are evolving and the extent to which lessons can be learned by looking outwards. We structure the paper by outlining the world of PSFs, its many manifestations and some of the current challenges in Section 2. We then move on to compare and interpret one particular leadership framework we developed to understand PSFs, and use this to identify some potential questions for higher education leaders. Finally, we conclude by exploring how, in the light of some of the current drivers of change, our view of the higher education sector may evolve as a new ‘eco-system’ emerges

Sustainability of non-residential buildings and relevance of main environmental impact contributors’ variability. A case study of food retail stores buildings

European tertiary sector represents about 13% of EU-28 final energy consumption. As an example, food retail stores sector amounts about 3% of EU members’ electricity consumption. Furthermore, currently, fluorinated gases, which are the most used refrigerants for space conditioning and refrigeration systems, involve 2% of EU emissions, having risen since 1990 by 60%. Specifically, commercial refrigeration is responsible for 35% of EU-27 CO2-eq emissions related to refrigerants. A methodology based on Life Cycle Assessment standards is presented in this study to assess the energy and environmental implications of non-residential buildings, adapted to particularities of food retail stores buildings, in terms of Primary Energy Demand, carbon footprint and water demand. Relying on a reference building, constructive improvements are tested and evaluated. Then a sensitivity analysis of several configurations of food retail stores are studied considering their building location, refrigerant typology and schedule. Results show that electricity and refrigerants are the main contributors and sensitive to potential improvements. In fact, static calculations reveal that a food retail store may involve, in terms of Global Warming Potential, about 800 kgCO2- eq/m2 year, more than 20 times higher than a regular building. Thus, future scenarios are estimated through a dynamic calculation methodology. Due to optimal dimensioning and configuration of the refrigeration system, together with refrigerant replacement, an 80% of Global Warming Potential minimization can be reached. Furthermore, temporal dynamic assessment can present a variability of environmental impacts estimation from static Life Cycle Assessment of more than 15%, by considering a wider approach towards sustainability assessment of non-residential buildings