scholarly journals Information Flows, Graphs and their Guessing Numbers

10.37236/962 ◽  
2007 ◽  
Vol 14 (1) ◽  
Author(s):  
Søren Riis

Valiant's shift problem asks whether all $n$ cyclic shifts on $n$ bits can be realized if $n^{(1+\epsilon)}$ input output pairs ($\epsilon < 1$) are directly connected and there are additionally $m$ common bits available that can be arbitrary functions of all the inputs. If it could be shown that this is not realizable with $m = O({n\over \log \log n})$ common bits then a significant breakthrough in Boolean circuit complexity would follow. In this paper it is shown that in certain cases all cyclic shifts are realizable with $m=(n- n^{\epsilon})/2$ common bits. Previously, no solution with $m < n - o(n)$ was known, and Valiant had conjectured that $m < n/2$ was not achievable. The construction therefore establishes a novel way of realizing communication in the manner of Network Coding for the shift problem, but leaves the viability of the common information approach to proving lower bounds in Circuit Complexity open. The construction uses the graph-theoretic notion of guessing number. As a by-product the paper also establish an interesting link between Circuit Complexity and Network Coding, a new direction of research in multiuser information theory.

2021 ◽  
Vol 2021 (2) ◽  
pp. 48-69
Author(s):  
Jean-Pierre Smith ◽  
Prateek Mittal ◽  
Adrian Perrig

Abstract With the meteoric rise of the QUIC protocol, the supremacy of TCP as the de facto transport protocol underlying web traffic will soon cease. HTTP/3, the next version of the HTTP protocol, will not support TCP. Current website-fingerprinting literature has ignored the introduction of this new protocol to all modern browsers. In this work, we investigate whether classifiers trained in the TCP setting generalise to QUIC traces, whether QUIC is inherently more difficult to fingerprint than TCP, how feature importance changes between these protocols, and how to jointly classify QUIC and TCP traces. Experiments using four state-of-theart website-fingerprinting classifiers and our combined QUIC-TCP dataset of ~117,000 traces show that while QUIC is not inherently more difficult to fingerprint than TCP, TCP-trained classifiers may fail to detect up to 96% of QUIC visits to monitored URLs. Furthermore, classifiers that take advantage of the common information between QUIC and TCP traces for the same URL may outperform ensembles of protocol-specific classifiers in limited data settings.


2000 ◽  
Vol 39 (02) ◽  
pp. 138-141
Author(s):  
H. Rix ◽  
O. Meste ◽  
W. Muhammad

Abstract:When several realizations of an unknown recurrent signal are observed apart from a time expansion or compression, the classical way of estimating these time scaling factors is to take one signal as reference for the estimation. This approach does not take into account the common information between all possible couples of realizations. To achieve this task we use a Maximum-Likelihood based method, in a sub-optimal manner. Using some realistic assumptions and simplifications, we propose a tractable solution. The improvement of classical results is shown through a simulation whose conclusion is that the larger the number of realizations, the more correct the estimation. Finally, we apply the method to electrically evoked sEMG.


2016 ◽  
Vol 14 (1) ◽  
pp. 94-104 ◽  
Author(s):  
Paul Skare ◽  
Herbert Falk ◽  
Mark Rice ◽  
Jens Winkel

2007 ◽  
Vol 2 (4) ◽  
pp. 80 ◽  
Author(s):  
Shelagh K. Genuis

A review of: Kuhlthau, Carol C. “Inside the Search Process: Information Seeking from the User's Perspective.” Journal of the American Society for Information Science 42.5 (1991): 361-71. Objective – To extend understanding of purposeful information seeking and to present a model of the information search process (ISP) from the perspective of the user. Design – Review of theoretical foundation, summing up of qualitative and quantitative data from a series of five foundational studies, and presentation of ISP model. Setting – Summarised research was conducted primarily in high school and college environments where subjects were investigating an assigned topic. A small proportion of public libraries were used in the fifth study within the reviewed series. Subjects – The ISP model as presented in this ‘classic’ article is based on studies involving a total of 558 participants. The first study involved 26 academically advanced high school seniors, and the 2 subsequent studies involved respectively 20 and 4 of the original participants following their completion of 4 years of college. The final 2 studies involved respectively 147 high, middle and low achieving high school seniors, and 385 academic, public and school library users. Methods – This paper presents the foundation for the ISP model by reviewing the relationship between Kelly’s personal construct theory, Belkin, Brooks, and Oddy’s investigation of cognitive aspects of the constructive information seeking process, and Taylor’s work on levels of information need (“Question-negotiation”) and value-added information (“Value-added”). This is followed by a review of Kuhlthau’s five foundational studies, which investigated the common information seeking experiences of users who were seeking to expand knowledge related to a particular topic or problem. The first of these studies was a small-scale exploration in which participants were given two assignments. Questionnaires, journaling, search logs, and reflective writing were used to collect data throughout the process of assignment completion. Data collection was augmented by case studies involving in-depth interviews and construction of timelines and flowcharts with six study participants. The six-stage ISP model was developed from qualitative content analysis of participants’ perceptions and experiences (Kuhlthau, “Library Research Process”). In the second study, the same questionnaire was used to determine how students’ perceptions of the ISP had changed over time. Post-college responses were compared to responses given in high school and statistical significance was determined through t Tests (Kuhlthau, Perceptions). Four of the original 6 case study participants were interviewed in the third study, in which interview data and search process timelines were compared with high school case studies (Kuhlthau, Longitudinal). In the fourth and fifth studies, large-scale field studies were conducted to verify the ISP model. Process surveys elicited participants’ thoughts and feelings at initiation, midpoint, and closure of a search task. Data were analysed using descriptive and inferential statistics including measures of significance and analysis of variance (Kuhlthau, Information Search; Kuhlthau et al.). Following a summation of these 5 research studies, this article details and discusses the ISP model. Main results – Based on the data from the five studies, the ISP presents a constructivist approach to information seeking and incorporates affective, cognitive, and physical dimensions at each of six information searching stages: initiation, topic selection, pre-focus exploration, focus formulation, information collection, and presentation. Individuals become aware of an information need at initiation. Feelings of uncertainty and apprehension are common as wide-ranging task exploration begins. At topic selection a general topic is selected and users frequently experience initial optimism, which is commonly followed by confusion and doubt as pre-focus exploration commences and users struggle to extend personal knowledge through initial investigation of the general topic. A turning point occurs during focus formulation as constructs become clearer and uncertainty decreases. During information collection the user is able to articulate focused need and is able to interact effectively with intermediaries and systems. Relief is commonly experienced at presentation stage when findings are presented or used. Although stages are laid out sequentially, Kuhlthau notes that the ISP is an iterative process in which stages merge and overlap. Central to this model is the premise that uncertainty is not due merely to a lack of familiarity with sources and technologies, but is an integral and critical part of a process of learning that culminates in finding meaning through personal synthesis of topic or problem. Conclusion – Kuhlthau provides evidence for a view of information seeking as an evolving, iterative process and presents a model for purposeful information searching which, if understood by users, intermediaries and information system designers, provides a basis for productive interaction. While users will benefit from understanding the evolving nature of focus formulation and the affective dimensions of information seeking, intermediaries and systems are challenged to improve information provision in the early formative stages of a search. Although Kuhlthau identifies this research on the ISP as exploratory in nature, this article affords methodological insight into the use of mixed methods for exploring complex user-oriented issues, presents a model that effectively communicates an approximation of the common information-seeking process of users, and provides ongoing impetus for exploring the user’s perspective on information seeking.


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