Compact Sketch Research Articles

Жизнь и творчество М.М. Бахтина глазами канадского исследователя

A review of K. Hirschkop’s book “The Cambridge introduction to Mikhail Bakhtin” is presented. The book by the renowned Canadian literary and cultural studies scholar Professor K. Hirschkop aims to give a systematic description of M.M. Bakhtin’s scientific heritage for the English-speaking reader, especially for a philology students’ audience. According to the reviewers, the author solves in this book both traditional tasks of a textbook, performed in the genre of «Introduction» as well as purely research tasks. For the first time in English-language Bakhtin Studies an analysis of the theory and practice of the Russian thinker is presented on the basis of the texts of his collected works, which Hirshkop is convinced forms the image of the “new” Bakhtin. The proven scheme of the Cambridge Introductions series allows the author to consistently present a compact sketch of the scholar’s life, the main sources and contexts of his philosophical and philological pursuits, an analysis of key ideas and works, and the process of reception in the English-speaking world of the second half of the 20th and early 21st centuries.

Accurately Estimating User Cardinalities and Detecting Super Spreaders Over Time

Online monitoring user cardinalities in graph streams is fundamental for many applications such as anomaly detection. These graph streams may contain edge duplicates and have a large number of user-item pairs, which makes it infeasible to exactly compute user cardinalities due to limited computational and memory resources. Existing methods are designed to approximately estimate user cardinalities, but their accuracy highly depends on complex parameters and they cannot provide anytime-available estimation. To address these problems, we develop novel bit/register sharing algorithms, which use a bit/register array to build a compact sketch of all users’ connected items. Our algorithms exploit the dynamic properties of the bit/register arrays (e.g., the fraction of zero bits in the bit array) to significantly improve the estimation accuracy, and have low time complexity <inline-formula><tex-math notation="LaTeX">$O(1)$</tex-math></inline-formula> to update the estimations for a new user-item pair. In addition, our algorithms are simple and easy to use, without requirements to tune any parameter. Furthermore, we extend our methods to detect super spreaders with large cardinalities in real-time. We evaluate the performance of our methods on real-world datasets. The experimental results demonstrate that our methods are several times more accurate and faster than state-of-the-art methods using the same amount of memory.

Streaming Algorithms for Estimating High Set Similarities in LogLog Space

Estimating set similarity and detecting highly similar sets are fundamental problems in areas such as databases and machine learning. MinHash is a well-known technique for approximating Jaccard similarity of sets and has been successfully used for many applications. Its two compressed versions, b-bit MinHash and Odd Sketch, can significantly reduce the memory usage of the MinHash, especially for estimating high similarities (i.e., similarities around 1). Although MinHash can be applied to static sets as well as streaming sets, of which elements are given in a streaming fashion, unfortunately, b-bit MinHash and Odd Sketch fail to deal with streaming data. To solve this problem, we previously designed a memory-efficient sketch method, MaxLogHash, to accurately estimate Jaccard similarities in streaming sets. Compared with MinHash, our method uses smaller sized registers (each register consists of less than 7 bits) to build a compact sketch for each set. In this paper, we further develop a faster method, MaxLogOPH++. Compared with MaxLogHash, MaxLogOPH++ reduces the time complexity for updating each coming element from O(k) with a small additional memory. We conduct experiments on a variety of datasets, and experimental results demonstrate the efficiency and effectiveness of our methods.

Sketch-based geometric monitoring of distributed stream queries

Emerging large-scale monitoring applications rely on continuous tracking of complex data-analysis queries over collections of massive, physically-distributed data streams. Thus, in addition to the space- and time-efficiency requirements of conventional stream processing (at each remote monitor site), effective solutions also need to guarantee communication efficiency (over the underlying communication network). The complexity of the monitored query adds to the difficulty of the problem -- this is especially true for nonlinear queries (e.g., joins), where no obvious solutions exist for distributing the monitor condition across sites. The recently proposed geometric method offers a generic methodology for splitting an arbitrary (non-linear) global threshold-monitoring task into a collection of local site constraints; still, the approach relies on maintaining the complete stream(s) at each site, thus raising serious efficiency concerns for massive data streams. In this paper, we propose novel algorithms for efficiently tracking a broad class of complex aggregate queries in such distributed-streams settings. Our tracking schemes rely on a novel combination of the geometric method with compact sketch summaries of local data streams, and maintain approximate answers with provable error guarantees, while optimizing space and processing costs at each remote site and communication cost across the network. One of our key technical insights for the effective use of the geometric method lies in exploiting a much lower-dimensional space for monitoring the sketch-based estimation query. Due to the complex, highly nonlinear nature of these estimates, efficiently monitoring the local geometric constraints poses challenging algorithmic issues for which we propose novel solutions. Experimental results on real-life data streams verify the effectiveness of our approach.

Virtual indexing based methods for estimating node connection degrees

It is difficult to accurately measure node connection degrees for a high speed network, since there is a massive amount of traffic to be processed. In this paper, we present a new virtual indexing method for estimating node connection degrees for high speed links. It is based on the virtual connection degree sketch (VCDS) where a compact sketch of network traffic is built by generating multiple virtual bitmaps for each network node. Each virtual bitmap consists of a fixed number of bits selected randomly from a shared bit array by a new method for recording the traffic flows of the corresponding node. The shared bit array is efficiently utilized by all nodes since every bit is shared by the virtual bitmaps of multiple nodes. To reduce the “noise” contaminated in a node’s virtual bitmaps due to sharing, we propose a new method to generate the “filtered” bitmap used to estimate node connection degree. Furthermore, we apply VCDS to detect super nodes often associated with traffic anomalies. Since VCDS need a large amount of extra memory to store node addresses, we also propose a new data structure, the reversible virtual connection degree sketch, which identifies super node addresses analytically without the need of extra memory space but at a small increase in estimation error. Furthermore we combine the VCDS and RVCDS based methods with a uniform flow sampling technique to reduce memory complexities. Experiments are performed based on the actual network traffic and testing results show that the new methods are more memory efficient and more accurate than existing methods.

“ON CONSULTING THE FAITHFUL IN MATTERS OF DOCTRINE”

SUMMARY In the foregoing article we tried to give a compact sketch of the process, which forced Newman to describe the place of the laity in ever more strict terms. The background is given in his vision on the doctrinal development, that characterizes the history of the church. The idea of Christianity is anchored in the believing community. There it unfolds its full reality. Later on, when there arise serious dangers for the Roman church in England, it is Newman, who puts his trust in the people, the faithful. Among them the religious truth comes to life. But they should be well instructed, able to justify themselves. This is a normal claim of society. A broad culture of mind is indispensable. It is quite natural, that Newman conceives sympathy for the “Rambler”. Here he meets laymen at work, who take their task seriously. As man, as citizen, as believer. But Newman has some reserves. He is opposed to every form of dilettantism. On a theological level a thorough formation is a necessity. Above all where ...