Improving associative classification by incorporating novel interestingness measures Abstract Classification and association-rule discovery are two of the most important tasks addressed in the data mining literature. In recent years, extensive research has been carried out to integrate both approaches. By focusing on a limited subset of association rules, i.e. those rules where the consequent of the rule is restricted to the class variables, it is possible to build more accurate classifiers. Several publications have shown that associative classification is intuitive and effective in many cases [1] [2] [3] [4] [5] . Normally, association rules search globally for all rules that satisfy minimum support and minimum confidence thresholds. The richness of the rules gives this technique the potential of reflecting the true classification structure in the data.. Associative classification is first proposed in CBA [2] , which uses the popular Apriori algorithm [6] to extract a limited number of association rules with their consequents limited to class labels. These rules are then sorted by descending confidence and pruned so as to get a minimal number of rules that are necessary to cover training data and achieve satisfying accuracy. Another associative classifier ADT [1] organizes the rule sets in the tree structure according to its defined relations. The decision tree pruning techniques is then applied to remove these rules much too specific. CPAR, CMAR and CAEP are three of the latest associative classification algorithms [3] [4] [5] . They propose expected accuracy, weighted chi-square and growth rate respectively as the rule interestingness measure, and all do classification based on multiple rules that the new sample fires. This paper devotes to improving CBA algorithm in order to generate more accurate and compact decision list (sequential classification rules), which is convenient for decision makers to understand. Instead of confidence, two novel interestingness measures, intensity of implication and dilated chi-square, are applied respectively as the primary sorting criterion. Both of these two measures statistically reveal the interdependence between the antecedence and consequence of the rule and empirically allocate the rules in a more reasonable sequence.. The remainder of the paper is arranged as follows. Section 2 introduces the basic concepts of the associative classification, along with the sorting mechanism applied by CBA. Section 3 elaborates on the weakness of conditional probability (confidence), as well as the design of intensity of implication and dilated chi-square to overcome it. The results of our empirical evaluation are shown in section 4. Section 5 gives our concluding remarks. Intensity of implication is proposed in the beginning as an interestingness measure for association rules. Another novel interestingness measure called dilated chi-square is designed by us to reveal the statistical interdependence between the antecedents and consequents of association rules.. We then adapt CBA algorithm, which can be used to build classifiers based on class association rules, by coupling it with intensity of implication and dilated chi-square respectively. More concretely, Intensity of implication (or dilated chi-square) is adopted as the primary criterion to rank class association rules at the first step of the database coverage pruning procedure in CBA algorithm. Experiments on three credit scoring datasets proved that these two adapted algorithms, compared with original CBA, classical C4.5 decision tree and neural network, achieve satisfactory performance and generates classifiers much more compact than CBA.

O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O B I I O B I O O O O O O O O O O O O O O O O O O O O B I I O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I O B I O O O B I I O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O


Can blog communication dynamics be correlated with stock market activity? In this paper, we develop a simple model to study and analyze communication dynamics in the blogosphere and use these dynamics to determine interesting correlations with stock market movement. This work can drive targeted advertising on the web as well as facilitate understanding community evolution in the blogosphere. We describe the communication dynamics by several simple contextual properties of communication, e.g. the number of posts, the number of comments, the length and response time of comments, strength of comments and the different information roles that can be acquired by people (early responders / late trailers, loyals / outliers). We study a "technology-savvy" community called Engadget (http://www.engadget.com). There are two key contributions in this paper: (a) we identify information roles and the contextual properties for four technology companies, and (b) we model them as a regression problem in a Support Vector Machine framework and train the model with stock movements of the companies. It is interestingly observed that the communication activity on the blogosphere has considerable correlations with stock market movement. These correlation measures are further crossvalidated against two baseline methods. Our results are promising yielding about 78% accuracy in predicting the magnitude of movement and 87% for the direction of movement. In this paper, we develop a simple model to study and analyze communication dynamics in the blogosphere and use these dynamics to mine interesting correlations with stock market movement. The problem is important because it provides insights into understanding communication patterns of people; for example, how context affects these patterns; how the information roles of people affect communication, temporal and topical dynamics of information roles etc. The communication dynamics further seem to yield correlations with certain external events as well, justifying their predictive power. Often, these dynamics are useful to corporate organizations who are interested in identifying the 'moods' of people on external communities in response to product releases and company related events. The dynamics can also drive targeted advertising on the web as well as enable understanding community evolution in the blogosphere.. There has been prior work on modeling communication dynamics [5, 7, 8] and their correlation with external events [4, 6] . The authors in [4] determine correlations between activity in Internet message boards (through frequency counts of relevant messages) and stock volatility and trading volume. In [6] the authors attempt to determine if blog data exhibit any recognizable pattern prior to spikes in the ranking of the sales of books on Amazon.com. They present hand-crafted predicates to show that correlation measures indicate visible blog mentions ahead of any evidence in sales rank. There has also been some work on identifying important bloggers based on communication activity in [9] . The authors attempt to determine 'hot' conversations in the blogosphere through agitators and summarizers by establishing discriminants. In [10] the authors identify opinion leaders who are responsible for disseminating important information to the blog network using a variation of the PageRank algorithm. However, modeling information roles and communication dynamics in the prior work have been done in a context-independent manner.. The main contribution of this paper is a simple contextual framework to model the communication dynamics among people and understand how they can be correlated with events external to the blogosphere. In this work, we have specifically looked at the impact on stocks of technology companies due postings in a gadgetdiscussing blog; however, the framework can be extended easily to other scenarios. We define stock movement of a company as the normalized difference between the returns on two consecutive days. We assume that the stock movement on a certain weekday can be correlated with the communication dynamics in the past week. This is reasonable because blog communication is often found to precede the occurrence of a real world event [6] . Hence we characterize the communication dynamics in a blog through several contextual features for a particular company. These contextual features are: the number of posts, the number of comments, the length and response time of comments, strength of comments and the different information roles that can be acquired by people (early responders / late trailers, loyals / outliers). We use these features and stock market movement of the company over N weeks for training an Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, or republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. SVM regressor. The trained parameters are used to predict the movement at the (N+1) th week. These results are validated using two baseline methods: firstly by comparing with a non-context aware case and secondly using a linear combination of the contextual features. Our technique supersedes both with error of 22 % and 13% in predicting the magnitude and direction of movement respectively.. The rest of the paper is organized as follows. In sections 2 and 3, we present a computational model for information roles and determining contextual features for stock movement prediction. Section 4 discusses the method of determining correlation between communication and stock movements. In section 5, we discuss some experimental results followed by conclusions and future work in section 6. In this paper, we have developed a simple model to study and analyze communication dynamics in blogosphere and use those dynamics to determine interesting correlations with stock market movement. We characterized the communication dynamics in a blog through several contextual features for a particular company. These contextual features were: the number of posts, the number of comments, the length of comments, response time of comments, strength of comments and the different information roles that can be acquired by people (early responders / late trailers, loyals / outliers). We used these features and stock market movement of the company over N weeks for training an SVM regressor. We predicted the stock movement using an incremental sample at N+1. Our technique supersedes two baseline methods with a mean prediction error of 22 % for magnitude and 13.41% for predicting the direction of movement.. There are several interesting directions to future work. We would like to improve our analysis of the information roles to identify people with variable consequences of their communication activity. The contextual model can also be refined by incorporating clustering of tags of companies, characterizing people by identifying response regions of their comments etc. It might also be interesting to see if there is an implicit macro property that underlies communication dynamics on the blogosphere and if that macro property is accounted for by a vocal minority or majority.

O O B I O O O B I O O O O O O O O O O O O O B I O O B O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O B O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O B O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O B I O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O B I O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O B O O O O O O O O O B I O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O B O O O O O O O O O O O O O O


Statistical relationships between journal use and research output at academic institutions in South Korea Abstract In this study, we analysed the statistical association between e-journal use and research output at the institution level in South Korea by performing comparative and diachronic analyses, as well as the analysis by field. The datasets were compiled from four different sources: national reports on research output indicators in science fields, two statistics databases on higher education institutions open to the public, and e-journal usage statistics generated by 47 major publishers. Due to the different data sources utilized, a considerable number of missing values appeared in our datasets and various mapping issues required corrections prior to the analysis. Two techniques for handling missing data were applied and the impact of each technique was discussed. In order to compile the institutional data by field, journals were first mapped, and then the statistics were summarized according to subject field. We observed that e-journal use exhibited stronger correlations with the number of publications and the times cited, in contrast to the number of undergraduates, graduates, faculty members and the amount of research funds, and this was the case regardless of the NA handling method or author type. The difference between the maximum correlation for the amount of external research funding with two average indicators and that of the correlation for e-journal use were not significant. Statistically, the accountability of e-journal use for the average times cited per article and the average JIF was quite similar with external research funds. It was found that the number of e-journal articles used had a strong positive correlation (Pearson's correlation coefficients of r [ 0.9, p \ 0.05) with the (2015 ( ) 103:751-777 DOI 10.1007( /s11192-015-1563 number of articles published in SCI(E) journals and the times cited regardless of the author type, NA handling method or time period. We also observed that the top-five institutions in South Korea, with respect to the number of publications in SCI(E) journals, were generally across a balanced range of academic activities, while producing significant research output and using published material. Finally, we confirmed that the association of e-journal use with the two quantitative research indicators is strongly positive, even for the analyses by field, with the exception of the Arts and Humanities. Usage statistics data by themselves are not a new phenomenon (Matthews 2009 ). Traditionally, libraries have maintained statistics records for gate counts, circulation, interlibrary loans, and information services (NISO 2007) . Academic libraries also frequently gather statistics on reserve items and submit reports to government agencies, parent institutions and library boards. Such information can then be used to understand work flow and improve library services. Since the rapid emergence of electronic resources and the explosion of online services becoming available through the internet, many institutions have acknowledged the benefits of investing in the collecting, reporting and analysis of usage statistics (Welch 2005) . Usage statistics for online resources have also been a primary analytical data source for public and private library consortia. The Virtual Library of Virginia consortia have undertaken a project to streamline, automate and standardize statistical data collection and the reporting process (Matthews 2009 ). Joint Information Systems Committee has been developing the Journal Usage Statistics Portal providing a 'one-stop-service' for librarians to view, download and analyze their usage reports. Since 2009, the Korea Institute of Science and Technology Information (KISTI) has consolidated the usage statistics of member institutions in order to provide integrated usage data with subscription and bibliographic information to members, as well as to monitor the use of e-journal packages distributed through the Korea Electronic Site Licensing Initiative (KESLI) consortia .. Recently, a number of researchers have attempted to measure scientific or research impact from usage data available online from publishers, aggregators, electronic resource management systems and link resolvers (Bollen et al. 2009 ). Larsen and Von Ins (2010) argued that the coverage of SCI has declined with the rapid growth of scientific publications. Existing citation databases such as WoS, Scopus and Google Scholar have limitations in coverage and depth for non-English language journals. Zainab et al. (2012) and Choi et al. (2013) argue that WoS and Scopus are comprehensive databases for English journals but do not adequately cover most national journals published in developing countries.. Usage data regarding PDF downloads, HTML views and SNS saves are considered as valuable, and complement traditional citation-based assessment metrics. The PLoS Medicine Editors (2006) predicted that new measures including the number of times downloaded, coverage in mainstream media, and times referenced in policy documents might be useful inputs to measure the impact of rarely cited but influential articles. ''Altmetrics'' builds on information from social media use, and is suggested to present a nuanced and multidimensional view of multiple research impact measures over time, together with traditional citation-based metrics (Priem and Piwowar 2012) . Bollen et al. (2009) analyzed and compared citation and usage networks, as well as various social network and hybrid measures to explore the most suitable methods for expressing and interpreting scientific impact. As a result, the 'Usage Closeness Centrality' incorporating 39 measures was deemed the best candidate for determining a 'consensus' view of scientific impact. Priem and Piwowar (2012) demonstrated that PDF downloads and HTML views correlate at moderate to high levels with almost all other Altmetrics. In particular, a moderately strong relationship between citation count and PDF/HTML download count for the three journals analyzed was reported in the study. Brody and Harnad (2005) postulated that if a correlation exists between citations and downloads, a higher rate of downloads in the first year of an article could be used to predict a higher number of eventual citations later. They identified an overall correlation of 0.4 between the citation numbers and download impact of articles in physics and mathematics archived in the UK's arXiv.org. Moed (2005) determined that during the first 3 months after an article is cited, the number of downloads increased 25 % compared to what would be expected had the article not been cited. In contrast, no relation between the usage factor and two measures of citation impact including the Journal Impact Factor and Elsevier's Source Normalized Impact per Paper (SNIP) metric was reported (CIBER Research Limited 2011) . Nevertheless, this particular report concluded that the new usage-based metric opens up the possibility of developing new ways of looking at scholarly communication, with different journals occupying very different niches within a complex ecosystem. Two reasons for the importance of download impact were highlighted by Brody and Harnad (2005) : (1) The proportion of download variance correlated with citation counts provides an early estimate of probable citation impact that can be tracked from the instant an article is made Open Access, and attains its maximum predictive power after 6 months; and (2) The portion of download variance that does not correlate with citation counts provides a second, partly independent estimate of the impact of an article, sensitive to another form of research usage that is not reflected in citation counts. In the same context, efforts to develop and substantiate usage-based metrics have been undertaken by several research groups (Bollen and Van de Sompel 2008; Gorraiz and Gumpenberger 2010) as well as the Counting Online Usage of NeTworked Electronic Resources (COUNTER) group (Shepherd 2011) .. It has generally been assumed that economic factors such as Gross Domestic Product (GDP), Gross Domestic Expenditures on Research and Development (GERD), and human resources have a linear or exponential relationship with research performance at the national level (Yoon 2007; Vinkler 2010) . According to Wood (1990) , personal characteristics and differences in research style, processes and techniques for research, as well as funding availability are the most important factors influencing the research productivity of academics. Heavy teaching loads were seen as a distraction from research activity in general. In particular, for the majority of science departments in academic institutions, the extent and continuation of funding are critical for facilitating research and many serious problems arise due to funding restrictions. However, to the best of our knowledge, there have been no previous studies investigating the statistical relationship between the production of resesarch publications and the use of them at the national or institutional level. Although the use of research publications is a daily necessity for researchers, investigations into the relationship between the use and production of research output at the institutional level in comparison to studies based on journal-specific metrics have been lacking.. In this study, our objective is to explore the relationship between research performance and the usage of publications at the level of institutions by performing comparative, diachronic analyses and an analysis by field. Specifically, we address the following three research questions:. 1. Which is most highly correlated with research output at the institutional level: human resources, economic factors or the use of research publications? 2. Does the extent of correlation of e-journal use with four research output measures for long term data differ when assessed from a short term perspective? 3. What is the statistical relationship between the use of research publications and research productivity at the institutional level (by field)?. Data, methodology and limitations

O O O O O O B I O O O O O O O O O O O O O O O O B I O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O B I O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O


Structural similarity-based object tracking in multimodality surveillance videos Abstract This paper addresses the problem of object tracking in video sequences for surveillance applications by using a recently proposed structural similarity-based image distance measure. Multimodality surveillance videos pose specific challenges to tracking algorithms, due to, for example, low or variable light conditions and the presence of spurious or camouflaged objects. These factors often cause undesired luminance and contrast variations in videos produced by infrared sensors (due to varying thermal conditions) and visible sensors (e.g., the object entering shadowy areas). Commonly used colour and edge histogram-based trackers often fail in such conditions. In contrast, the structural similarity measure reflects the distance between two video frames by jointly comparing their luminance, contrast and spatial characteristics and is sensitive to relative rather than absolute changes in the video frame. In this work, we show that the performance of a particle filter tracker is improved significantly when the structural similarity-based distance is applied instead of the conventional Bhattacharyya histogram-based distance. Extensive evaluation of the proposed algorithm is presented together with comparisons with colour, edge and mean-shift trackers using real-world surveillance video sequences from multimodal (infrared and visible) cameras. Recently there has been an increasing interest in target tracking in video sequences that is of particular importance to military and civilian surveillance applications [10, 11, 9, 27, 20, 12] . Various methods for object tracking in video sequences were proposed in the literature. Bayesian methods are the most often used where the problem reduces to the reconstruction of the probability density function of the object states given the measurements and the prior knowledge. Different image features such as colour, motion, edges, shape and texture can be used to track the moving object [27, 24] . This problem presents many challenges, including how to model the moving object, the choice of measurement model and the function characterising the similarity between two images or video frames. One specific issue with object tracking in video sequences (compared to, for example, tracking with radar data) is that no measurement model exists in explicit form.. Multiple feature-based tracking provides more information about the object and hence increases the robustness of the algorithms to occlusions and clutter. An optimisation approach for different features selection is proposed in [33] which is embedded in a layered hierarchical vision-based tracking algorithm. When the target is lost, the layers cooperate to perform a rapid search for the target and continue tracking. Features can be implemented concurrently in the democratic integration approach [34] and contribute simultaneously to the overall result. Some other methods rely on applying tensor theories to visual surveillance, e.g. for gait recognition [31, 32] .. The performance of the tracking algorithm, however, also depends on the measure characterising the similarity between the two subsequent video frames. Frequently used functions include the Bhattacharyya distance [1, 6] and the non-metric Kullback-Leibler measure.. In this paper we propose a particle filter (PF) based on a structural similarity measure for object tracking in video sequences. The PF framework has been proven to be a scalable and powerful approach, able to cope with non-linearities and uncertainty present in video sequences (see, for example, [27, 25, 3, 4] ). In this work, we combine these strengths of the particle filtering with the properties of the structural similarity measure. The similarity measure proposed in [37] captures the spatial characteristics of an image and has been shown to be robust to illumination and contrast changes. The way this measure is formulated reflects the fact that the Human Visual System (HVS) is highly adapted to extract structural information from the visual scene [38] . It has been originally used for the purposes of quality assessment of distorted and fused images [37, 28, 18] . In this paper, we show how this measure can be applied to the video tracking problem. It replaces histograms used for calculation of the measurement likelihood function within a particle filter. We demonstrate that it is a good and efficient alternative to histogram-based tracking. This work extends the early results reported in [19] with more detailed investigation including the consideration of tracking in multimodality and fused videos. The performance of the proposed method is compared with results obtained with a PF using the Bhattacharyya distance (some of which have been reported in [21] ) and mean-shift tracker [5] , both applied to multimodality and fused videos.. The remaining part of the paper is organised as follows. Section 2 presents the structural similarity-based distance for tracking. Section 3 presents a PF with the proposed similarity measure, describes the likelihood and motion model of the object of interest. Section 4 contains results over real-world video sequences. Finally, Sect. 5 summarises the results and discusses open issues for future research. A new tracking scheme based on structural similarity has been developed and has been shown to perform reliably under difficult conditions (as often occurs in surveillance videos), when tested with real-world video sequences. Robust performance has been demonstrated in both low and variable light conditions, and in the presence of spurious or camouflaged objects. In addition, the algorithm copes well with the artefacts that may be introduced by a human operator, such as rapid changes in camera view angle and zoom. This is achieved with relatively low computational complexity, which makes our algorithm potentially applicable to real-time surveillance problems.. Colour cue itself cannot provide stable tracking under changing illumination and when regions with similar colour are present in the scene. Likewise, the combined colour and edge cue, although generally performing well, cannot provide a reliable and precise tracking performance under ambiguous situations, especially with a moving camera (with changes in the pan, tilt and zoom). In contrast, the proposed PF based on the structural similarity measure exhibits the most stable and reliable performance. This is due to the fact that this measure captures the spatial similarity between Fig. 7 Example video frames with a tracker output (tracking rectangle and particles) superimposed, sequence S1-T1-C containing a rotating object the regions of interest, independently of the colour. It measures only relative changes in contrast and luminance, and thus is more robust to the changes in the environment. The implemented tracking algorithm uses a changeable size of the tracking window, which makes it suitable for many realworld applications (where the camera-object distance varies significantly).. Future work on the proposed PF tracking approach will be focussed on further improvement of its performance by realising the potential of giving adaptive weights to the three components of the similarity measure in (7) . The structural similarity measure-based tracker may not be robust to significant alteration of the tracked object. Thus, the recovery and/or template update techniques will also be investigated in the future to improve reliability of the proposed tracker.

O O B I O O O O O O O O O O O B I O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O B I O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I O B I O B I O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O B I O O O O O B I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O


Production of pace as collaborative activity In this paper we investigate the concept of pace development and management among groups of people. We explore and compare groups visiting museums, and groups virtually co-located in a mixed reality system for a museum. In considering pace, and how to design to support it, we have to consider more than the speed or location of information display. We have to also take into consideration the social formation of pace through features such as the visitors' awareness of each other's location and attention. By considering aspects of collaboratively produced pace such as presenting engagement and disengagement, we offer suggestions as to how social handling of pace might be better supported by technology. In recent years, the demand for personalisation of the user experience and the technological push from new hardware developments have led to the research and development of personal mobile devices that offer access to information on the move. These devices are increasingly directed towards leisure activities such as tourism, sightseeing and museum visiting. Commercial products such as audioguides and map tools have become more widespread, and research work continues to explore new possibilities for information display [5, 9] and social interaction around such information [1, 3] .. Researchers and developers often make indirect claims of supporting exploration of information at the individual user's pace, although pace itself has not often been discussed explicitly, with [6] being a notable exception. The social management or handling of the pace of interaction also arises indirectly in studies of collaboration and collaborative systems, and it would seem that the collaborative production and handling of pace is an important aspect of the overall user experience, but relatively little has been published that focuses on pace in detail, especially with regard to how groups handle the combination of their interaction around artifacts and displays, and their interaction with each other.. Pace is commonly defined as the manner of stepping or running, as well as the speed or rate of progress. It refers to movement within geometric or geographic space as well as the rate of accomplishing an activity such as speaking or reading. When pace is used to describe movement through space it also carries a sense of directionality or directedness, hence progress toward a goal. One's pace is also influenced by time constraints and features of the environment, such as terrain, crowds, mode of transport and so forth.. Although, individuals may have their own pace in accomplishing an activity, there are many situations where social aspects of pace are also important, and each individual's pace is affected by and affects others'. This is a common part of everyday life when people walk with their friends on the street, go shopping together or visit an exhibition. Groups of people often take part in sporting activities such as hillwalking, cycling and horseriding, and clubs often organise 'social pace' events [4] , i.e. excursions that are done in a relaxed manner "with plenty of opportunities to smell the roses, view the scenery, and stop at bakeries or other refreshment locations". These events are meant to appeal to a variety of members and offer the opportunity for socialising as well as exercising, with the promise that "nobody will be dropped or left alone".. Audio guides in museums are often used for pace management purposes so people who listen to the commentaries do not crowd up in front of a display but move evenly around the exhibition. Specifically in well attended 'blockbuster' exhibitions, the audio commentaries are designed to impose both a certain speed as well as direction to visitors, prompting them to move on along a route. On the other hand, research in wearable computers and digital tourist guides [10] utilised accelerometers to infer one's activity from one's pace, for example whether the user is sitting, running etc., so as to make available appropriate information. In group situations, pace has been associated with coordination, for example in studies of tourists [3] , hunters [11] , and mobile game players [8] . Coordination among group members is often done explicitly via talk, e.g. via mobile phones, and also via awareness of location, as may be supported by systems for location tracking and display, e.g. active badges and media spaces [7] , Hummingbirds [15] , and mixed reality systems [2] . This paper looks beyond coordination, and considers its relationship to individual attention and self-presentation, meaning the public presentation of one's engagement and activity. We discuss visibility, pausability and embodied interaction, drawing examples from visiting activity among collocated and non-collocated museum visitors. We draw examples from a visitor study of non-educational groups of visitors in two cultural institutions in Glasgow and a user study of a mixed reality system that supported the simultaneous shared exploration of a gallery by a group of visitors who were not collocated. Reflecting on these issues and on the way that current technologies use and support pace, we put forward issues and suggestions for future system designs intended to better fit and support the shared visit experience. We believe that as more applications move towards the support of collaborative leisure activities, support of pace will become an important element of smooth and enjoyable shared experiences. In this paper we drew examples from a museum visiting experience among collocated and noncollocated visitors to discuss location awareness and visibility as resources of pace production. We also argued that those resources need to be coupled with effective selfpresentation and expression of various degrees of engagement to support the collaborative production of pace and enhance the shared experience. In this paper so far we looked at the ways pace is collaboratively produced during a museum visit. We also discussed our experience from a mixed reality museum environment that primarily supported collaborative production of pace through location awareness and verbal communication. In our observations of museum visitors we found out that presentation of self plays an important role in the collaborative production of pace, as one makes available the various degrees of engagement with an activity and one's own intentions to move on. With existing technologies for such shared visits, it may be difficult to engage with information about a location or artefact, while also indicating via location or gesture that one is ready to move on from that artefact. Similarly, it may be difficult to use a tool for the display of information about a location or artefact without losing awareness of others' movement and gesture. Simple avatars and map icons often lack the subtlety of expression required to produce the necessary implicit cues for shared pace.. It may then be that the design of systems for such shared visits should take this dual presentation into account, either by dual displays or regions of a display. Alternatively, one might use multiple media so that one tool or medium shows detail of an artefact or location, while another tool or medium that lets one see/hear what is going on with other artefacts and locations. An example is the use of spatialised audio to show the direction/distance/talk of co-visitors, while one focuses on some detailed graphics. Similarly, audio display of information can be complemented by a graphical map that affords enough peripheral awareness of others to let one decide when to move on. Additionally, members of a group could be digitally tied together, hence have the opportunity to mark objects, or produce markers, so as to attract their friends, or even to explicitly change other's field of view.. This short paper has presented an initial exploration of the issues behind collaborative production of pace in leisure group activities. Two strands of future investigation would be possible: the first to further compare pace production among users in the physical space and users in a VE, and among the former and users of a hypermedia environment; the second, to further examine the role of collaborative production of pace in the sense of presence and togetherness and whether this aspect of togetherness is worth pursuing in a mixed reality environment. Hopefully, we will come back on that soon.

O O B O O O O O O O O O O O B O O O O O O O O O O O O O B O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O B O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O B O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O B O B I O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O


The Correlation Conversion Property of Quantum Channels Transmission of quantum entanglement will play a crucial role in future networks and longdistance quantum communications. Quantum Key Distribution, the working mechanism of quantum repeaters and the various quantum communication protocols are all based on quantum entanglement. On the other hand, quantum entanglement is extremely fragile and sensitive to the noise of the communication channel over which it has been transmitted. To share entanglement between distant points, high fidelity quantum channels are needed. In practice, these communication links are noisy, which makes it impossible or extremely difficult and expensive to distribute entanglement. In this work we first show that quantum entanglement can be generated by a new idea, exploiting the most natural effect of the communication channels: the noise itself of the link. We prove that the noise transformation of quantum channels that are not able to transmit quantum entanglement can be used to generate distillable (useable) entanglement from classically correlated input. We call this new phenomenon the Correlation Conversion property (CC-property) of quantum channels. The proposed solution does not require any non-local operation or local measurement by the parties, only the use of standard quantum channels. Our results have implications and consequences for the future of quantum communications, and for global-scale quantum communication networks. The discovery also revealed that entanglement generation by local operations is possible.Keywords: Quantum communication, quantum entanglement, correlation conversion, quantum Shannon theory.One of the most important goals of current research in quantum computation and communications is the development of global-scale quantum communication networks. The success of worldwide Quantum Key Distribution and quantum repeater networks is based on quantum entanglement [1][2][3][4][5][6][7]. On the other hand, the process of entanglement sharing and distribution is an expensive task. The practical quantum channels are noisy, which makes it very hard or even impossible to send entangled particles over these links. The main reason is that quantum information is very fragile and extremely sensitive to the noise of the communication links. The current solutions under development for entanglement transmission are based on various entanglement purification methods, which could make it possible to share entanglement between distant points, but only if the noise of the communication links is low enough to allow the realization of the post-purification processes in the nodes. However, these purification methods are very expensive and inefficient, since many entangled pairs have to be shared between the parties with relatively high fidelity. One of the most fundamental questions in the development of future communication networks is the process of entanglement transmission. If it were possible to find quantum channels that could generate entanglement between two distant points (let us refer to them as Alice and Bob) without sending the entanglement itself, then we could dramatically reduce the cost of development of future quantum communication networks. It would also have very serious consequences for current knowledge about the nature of the information itself.Over a quantum channel  , many types of information can be transmitted. Sending entanglement would be possible only if the noise of channel  is low (i.e., it is a high fidelity channel which can transmit quantum information). On the other hand, if the noise of  is high (assuming it is a practical communication channel) then entanglement might be transmitted with much difficulty, or it could be completely impossible.Let us assume that there is a quantum channel  between Alice and Bob, which is so noisy that it cannot function as a transmission venue for any quantum information, but it can be used to send classical information over it (i.e., it has quantum capacity ( ) = In that case the problem of entanglement sharing would be reduced to the following process:Alice prepares a classically correlated system, AB, in which she keeps A and feeds B to channel  . Bob receives B, and the result is quantum entanglement between Alice and Bob, generated simply by the noise of the channel.If it were possible, Alice could use the classical-quantum channel  to send entanglement to Bob, except for the fact that she prepared a classically correlated input and the channel can transmit classical correlation only. This idea might seem to be unimaginable and completely impossible at first sight, and our intuitions also strictly dictate that it cannot be true.Up to this point, the possibility of entanglement generation between Alice and Bob has been based on the transmission of quantum entanglement, which requires high fidelity quantum channels between the parties. (Holevo-Schumacher-Westmoreland) setting to describe the transmission of classical information over quantum channels. However, from the "classical-quantum" term it does not follow unambiguously that the quantum channel could not transmit quantum correlations. In our setting, under the "classical-quantum channel" we mean only those quantum channels that can transmit classical correlations, only.* The term "classical-quantum channel" has several different interpretations in the literature. It is used mainly in the HSWAs we have found, this is not the case. There exist low fidelity channels which can transmit only classical correlation, but the noise transformation of the channel can re-transform the input density matrix in such a way that it will result in quantum entanglement between Alice and Bob.From this point onward, Alice has a much better choice than to send the entanglement directly over  . Alice can feed only a classically correlated input system to  , and the process of entanglement transmission will be made by the most natural property of these communication channels: by the noise transformation of the channel, itself. We called this new phenomenon the "Correlation Conversion" property (CC-property) of quantum channels. Producing entanglement from classical correlation by the noise of quantum channels seemed to be impossible before our results. However, it has already been shown that separable states can be used to distribute entanglement [8][9][10][11][12], but these protocols require ideal or nearly noiseless channels between Alice and Bob, which is completely unattainable in a practical communication sys-5 tem. These schemes also have another drawback: the requirement of non-local operations and local measurement. Our solution does not require ideal channels nor any non-local operation or local measurement on the encoder or decoder side to generate distillable quantum entanglement, only the use of standard quantum channels, i.e., local operations [15]. of the second channel will be also received by Bob, and will be simply traced out in the calculations. The final system state will be referred to asTr , in which the system state will contain quantum entanglement between r A and s B .We can easily find such kinds of channels; for example, any channel  1 with error probability Legends Fig. 2 . The CC-property of quantum channels. Neither channel  1 nor  2 can transmit any quantum information or distillable entanglement (i.e., these channels are referred as classical-quantum channels); however, the noise transformation of the channels can generate distillable quantum entanglement between r A and s B from classically correlated, unentangled inputs, r A and r B .To measure the amount of noise-generated distillable entanglement we consider the use of the r r r r r r r r = = -min min log logwhere r AB is the set of separable states r r r. As we have found, the following connection holds for the amount of noise-generated entanglement. ,where In this work we first proved that distillable quantum entanglement can be produced by the noise transformation of classical (low fidelity) channels, the result of which has severe consequences for future quantum communications. Our results make it possible to generate distillable entanglement between distant points from classically correlated inputs over quantum channels that have no capability of transmitting quantum information. We developed a new idea which exploits the most natural property of the communication channels and which opens new dimensions in the fields of quantum communications. The solution does not require any non-local operation or local measurement by the parties, only the use of standard quantum channels. It also constrains us to revise our current knowledge about quantum channels and the nature of information itself. We 9 have to reveal those deeply involved, currently hidden and uncharacterized possibilities that quantum information still holds. In this work we first proved that distillable quantum entanglement can be produced by the noise transformation of classical (low fidelity) channels, the result of which has severe consequences for future quantum communications. Our results make it possible to generate distillable entanglement between distant points from classically correlated inputs over quantum channels that have no capability of transmitting quantum information. We developed a new idea which exploits the most natural property of the communication channels and which opens new dimensions in the fields of quantum communications. The solution does not require any non-local operation or local measurement by the parties, only the use of standard quantum channels. It also constrains us to revise our current knowledge about quantum channels and the nature of information itself. We have to reveal those deeply involved, currently hidden and uncharacterized possibilities that quantum information still holds.

O B I O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O B I O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O B I B I B I O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O


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a

key

component

in

future

shared-memory

multi-core

or

multi-processor

systems.

The

state

space

explosion

is

the

first

hurdle

while

applying

model-checking

to

scalable

protocols.

In

order

to

validate

parameterized

cache

coherence

protocols

effectively,

we

present

a

new

method

of

reducing

the

state

space

of

parameterized

systems,

two-dimensional

abstraction

(TDA).

Drawing

inspiration

from

the

design

principle

of

parameterized

systems,

an

abstract

model

of

an

unbounded

system

is

constructed

out

of

finite

states.

The

mathematical

principles

underlying

TDA

is

presented.

Theoretical

reasoning

demonstrates

that

TDA

is

correct

and

sound.

An

example

of

parameterized

cache

coherence

protocol

based

on

MESI

illustrates

how

to

produce

a

much

smaller

abstract

model

by

TDA.

We

also

demonstrate

the

power

of

our

method

by

applying

it

to

various

well-known

classes

of

protocols.

During

the

development

of

supercomputer

system,

TDA

was

used

to

verify

the

coherence

protocol

in

CPU

and

showed

the

potential

advantages

in

reducing

the

verification

complexity.

Model

checking

is

an

automatic

technique

for

verifying

finite

state

concurrent

systems,

which

uses

a

finite

state

machine

to

describe

the

system

under

consideration

and

temporal

logic

to

state

the

properties

that

the

system

must

satisfy.

This

method

has

been

used

successfully

in

practice

to

verify

complex

software

and

hardware

systems

However,

efficient

verification

of

parameterized

cache

coherence

protocols

is

one

of

the

most

challenging

problems

in

verification

domain

today.

Firstly,

parameterized

systems

are

composed

of

an

arbitrary

number

of

processes

which

concur

cooperatively

(the

number

of

processes

is

called

the

system

parameter).

The

behavior

of

one

process

is

determined

not

only

by

its

current

state,

but

also

the

changes

of

the

environment

it

lives.

Secondly,

parameterized

systems

are

by

nature

unbounded.

The

system

parameter

may

be

arbitrarily

large,

and

the

ultimate

goal

is

to

validate

the

properties

in

a

system

for

every

possible

number

of

processes.

In

such

cases,

the

number

of

global

states

can

be

enormous,

resulting

in

the

state

space

explosion.

Formal

verification

of

parameterized

systems

is

known

to

be

undecidable

and

thus

cannot

be

automated.

Thirdly,

symbolic

methods

such

as

BDD

or

SAT,

which

can

enable

scalable

formal

verification

methods,

can

be

ineffective

when

it

comes

to

cache

coherence

protocols

because

most

of

the

state

variables

are

relevant

in

protocol

property

verification.

As

faster

larger

systems

are

designed,

the

complexity

of

cache

protocols

will

continue

to

increase..

Fong

Pong

presented

a

comprehensive

survey

of

various

approaches

to

the

verification

of

cache

coherence

protocol

based

on

state

enumeration,

model

checking,

and

symbolic

state

models.

He

pointed

out

that

no

framework

had

been

proposed

so

far

to

deal

with

the

memory

consistency

model

in

the

context

of

formal

verification

based

on

state

expansion.

Monolithic

formal

verification

methods

that

treat

the

protocol

as

a

whole

have

been

used

fairly

routinely

for

verifying

cache

coherence

protocols

from

the

early

However,

these

monolithic

techniques

will

not

be

able

handle

the

very

large

state

space

of

parameterized

protocols.

While

techniques

like

indexed

predicates

counter

abstraction

environment

abstractions

and

cutoffs

based

approach

have

been

proposed

for

parameter

protocol

verification

during

these

years,

of

them

scales

well

to

large

protocols,

and

those

that

do

scale

require

an

inordinate

amount

of

manual

effort

to

succeed

We

are

not

aware

of

any

published

work

that

has

reported

formal

verification

of

a

parameterized

cache

coherence

protocol

with

reasonable

complexity..

All

successful

applications

of

model

checking

thus

far

have

made

use

of

domain

specification

abstraction

techniques.

Continuing

this

trend

and

drawing

inspiration

from

recent

work

like

environment

abstraction

we

exploit

the

domain

knowledge

about

parameterized

systems

to

devise

an

appropriate

abstraction

method.

We

propose

a

novel

generic

approach

called

two-dimensional

abstraction

(TDA),

which

could

effectively

reduce

the

state

space

of

parameterized

systems.

In

our

work,

the

size

of

the

state

transition

graph

for

each

process

is

reduced

independently

at

first,

then

the

whole

system

composed

of

the

reduced

processes

is

abstracted

based

on

the

design

principles

of

parameterized

systems,

thus

avoiding

the

construction

of

the

complete

state

space

that

might

be

too

large

to

fit

into

memory..

TDA

has

a

number

of

advantages

over

other

approaches.

First,

TDA

abstracts

away

redundant

information

from

a

concrete

system

via

decomposition-abstractioncomposition-reabstraction,

thus

effectively

alleviating

the

state

explosion

problem

during

parameterized

systems

verification.

Second,

TDA

can

be

used

for

parallel

systems

in

the

usual

fashion

because

it

has

no

limitation

in

communication

mode

among

processes.

Third,

TDA

can

be

used

with

any

model

checker.

The

freedom

to

choose

model

checkers

is

important

in

practice.

Fourth,

TDA

is

sound

and

complete.

We

give

complete

soundness

and

completeness

proofs

for

our

method.

At

last,

constant

heterogeneous

processes

and

infinite

state

systems

are

allowed,

which

makes

TDA

suitable

for

large

scale

heterogeneous

systems.

We

demonstrate

the

power

of

our

method

by

applying

it

to

various

well-known

classes

of

protocols..

The

rest

of

this

paper

is

organized

as

follows.

In

Sect.

we

introduce

previous

related

work.

Section

gives

some

background

information.

In

Sect.

we

propose

a

model

with

true

concurrency

semantics

for

parameterized

systems.

In

Sect.

we

present

concepts

of

a

TDA

model

and

the

method

to

construct

a

TDA

model.

A

cache

coherence

protocol

based

on

MESI

is

used

to

illustrate

the

approach

of

getting

a

much

smaller

state

space

by

TDA

in

Sect.

Experimental

results

of

various

well-known

protocols

and

application

are

presented

in

Sect.

Section

the

last

section,

presents

concluding

remarks.

The

verification

of

cache

coherence

in

general

is

known

to

be

NP-hard.

In

the

age

of

exascale

computing,

scalability

is

emerging

as

one

of

the

key

components

in

parallel

computing

Scalable

multi-core

multi-processor

architectures

are

inevitable.

More

and

more

complex

processes

and

unbounded

system

parameter

result

in

the

state

explosion

during

the

verification

of

parameterized

cache

coherence

protocols.

A

generic

abstraction

method

for

parameterized

systems,

two-dimensional

abstraction

(TDA),

has

been

put

forward

in

this

paper.

The

novelty

of

our

approach

lies

in

that

it

analyzes

in

depth

the

intrinsic

factors

affecting

the

size

of

state

space,

and

reduces

the

state

space

in

two

dimensions,

thus

a

much

smaller

abstract

model

is

produced.

Compared

with

traditional

approaches,

our

approach

can

effectively

reduce

the

verification

complexity

and

greatly

scale

the

verification

capabilities.

We

give

complete

soundness

and

completeness

proofs

for

our

method.

We

have

demonstrated

the

benefits

of

our

approach

on

several

coherence

protocols

with

realistic

features.

Our

future

work

is

to

integrate

TDA

with

model-checking

tools

and

check

the

advanced

cache

coherence

protocol

hierarchically

organized

for

a

next

generation

supercomputer.

We

also

plan

to

investigate

combining

TDA

with

CMP

method

in

the

future.

The

development

of

effective

techniques

for

checking

parameterized

systems

is

one

of

the

most

challenging

problems

in

verification

today.

Prior

research

in

the

area

of

coherence

protocol

verification

has

ranged

from

simulation

to

formal

methods.

These

techniques

have

had

varying

degrees

of

success,

but

few

of

them

have

been

applied

to

a

large

industrial-strength

protocol

like

FLASH..

Simulation

with

random

or

directed

stimulus

has

been

shown

to

be

effective

at

finding

most

protocol

errors

However,

simulation

tends

not

to

be

effective

at

uncovering

subtle

bugs,

especially

those

related

to

the

consistency

model.

Subtle

consistency

bugs

often

occur

only

under

unusual

combinations

of

circumstances,

and

it

is

unlikely

that

simulation

will

drive

the

protocol

to

these

situations..

For

verification

of

high

level

specifications,

modern

industrial

practice

consists

of

modeling

small

instances

of

the

protocols

in

guard/action

languages

such

as

Murphi

or

TLA+

and

exploring

the

reachable

states

through

explicit

state

enumeration..

The

idea

of

using

non-interference

lemmas

for

parameterized

model

checking

is

attributed

to

McMillan

Chou

and

Li

which

is

also

called

the

CMP

method.

The

CMP

approach

to

parameterized

verification

is

a

combination

of

data

type

reduction

and

compositional

reasoning.

In

this

approach,

a

model

checker

is

used

as

proof

assistant

and

the

user

guides

the

proof

by

supplying

invariants

or

noninterference

lemmas.

Similar

types

of

reasoning

have

been

applied

by

Chen

to

verify

non-parameterized

hierarchical

protocols

The

compositional

method

of

McMillan

is

used

for

compositional

reasoning

to

handle

infinite

state

systems

including

directory

based

protocols.

This

technique,

which

requires

user

intervention

at

various

stages,

has

been

applied

to

verify

safety

and

liveness

properties

of

the

FLASH

protocol.

The

paper

by

Chou

presented

a

method

along

similar

lines,

that

was

used

to

verify

safety

of

FLASH

and

GERMAN

protocol.

Krstic

gave

a

formalization

of

the

method.

The

CMP

method

scales

well.

As

far

as

we

are

aware,

the

CMP

method

is

one

of

a

few

methods

to

handle

the

full

complexity

of

the

FLASH

protocol.

Intel

used

CMP

to

verify

an

industrial-strength

cache

protocol

several

orders

of

magnitude

larger

than

even

the

FLASH

protocol

Talupur

and

Tuttle

showed

how

to

derive

high-quality

invariants

from

message

flows

and

how

to

use

these

invariants

to

accelerate

the

CMP

method

A

message

flow

is

a

sequence

of

messages

sent

among

processors

during

the

execution

of

a

protocol.

The

hardest

part

of

using

CMP

is

finding

a

set

of

protocol

invariants

that

enable

CMP

to

work.

The

user

has

the

burden

of

coming

up

with

non-interference

lemmas

which

can

be

non-trivial

and

require

deep

understanding

of

the

protocol

under

verification..

Another

effective

method

for

parameterized

verification

is

the

abstraction

approach

Predicate

abstraction,

first

proposed

by

Graf

as

a

special

case

of

the

general

framework

of

abstraction

interpretation,

has

been

used

in

the

verification

of

parameterized

protocols.

In

predicate

abstraction,

a

finite

set

of

predicates

is

defined

over

the

concrete

set

of

states.

These

predicates

are

used

to

construct

a

finite

state

abstraction

of

a

concrete

system.

The

automation

in

generating

the

finite

abstract

model

makes

this

scheme

attractive

in

combining

deductive

and

algorithmic

approaches

for

infinite

state

verification.

Lahiri

proposed

the

use

of

a

symbolic

decision

procedure

and

its

application

for

predication

abstraction.

One

of

the

main

problems

in

predicate

abstractions

is

that

it

typically

makes

a

large

number

of

theorem

prover

calls

when

computing

the

abstract

transition

relation

or

the

abstract

state

space.

Pnueli

presented

the

method

of

invisible

invariants

that

combines

a

smallmodel

theorem

with

a

heuristics

to

generate

proofs

of

correctness

of

parameterized

systems.

Wang

used

monotonic

abstraction

to

provide

an

over-approximation

of

the

transition

system

induced

by

a

parameterized

system.

The

over-approximation

gives

a

transition

system

which

is

monotonic

with

respect

to

a

well

quasi-ordering

on

the

set

of

configurations.

Timm

presented

an

approach

combining

symmetry

arguments

with

spotlight

abstractions.

The

technique

determines

(the

size

of)

a

particular

instantiation

of

the

parameterized

system

from

the

given

temporal

logic

formula,

and

feds

this

into

an

abstracting

model

checker.

Environment

abstraction

exploits

the

replicated

structure

of

a

parameterized

system

to

make

its

verification

easy,

and

it

converts

the

unbounded

system

into

a

bounded

one

via

finite

state

description

method.

In

real

cache

coherence

protocols,

the

internal

state

of

each

cache

can

be

quite

complex,

and

thus

environment

abstraction

might

fail.

The

other

method

is

divide-and-conquer,

in

other

words,

abstraction

for

each

process

is

made

independently

before

the

model

for

the

whole

system

is

constructed

Unfortunately,

too

many

constraints

for

systems

under

consideration

make

this

way

unpractical..

Other

related

work

includes

that

of

Pandav

who

has

proposed

a

set

of

heuristics

to

aid

in

constructing

invariants

for

cache

protocols.

Delzanno

used

arithmetic

constraints

to

model

possibly

infinite

sets

of

global

states

of

a

multi-processor

system

with

many

identical

caches.

General

purpose

symbolic

model

checkers

for

infinite-state

systems

working

over

arithmetical

domains

were

used.

Delzanno

and

Bultan

described

a

constraint

based

verification

method

for

handling

the

safety

and

liveness

properties

of

GERMAN

protocol.

But

their

method

cannot

verify

single

index

liveness

properties.

Emerson

and

Kahlon

verified

GERMAN

by

first

reducing

it

to

a

snoopy

bus

protocol

and

then

invoking

a

theorem

asserting

that

if

a

snoopy

bus

protocol

of

a

certain

form

is

correct

for

nodes

then

it

is

correct

for

any

number

of

nodes.

Pnueli

proposed

an

elegant

cutoff

method

that

can

verify

the

DIR

protocol

but

it

was

sound

and

not

complete,

and

worked

only

for

safety

properties.

A

broad

technique

was

proposed

for

the

verification

of

WSIS

systems

that

can

handle

the

DIR

protocol

as

an

example

yet

again

the

resulting

technique

was

sound

but

not

complete.

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Sparse Modeling of Textures Abstract This paper presents a generative model for textures that uses a local sparse description of the image content. This model enforces the sparsity of the expansion of local texture patches on adapted atomic elements. The analysis of a given texture within this framework performs the sparse coding of all the patches of the texture into the dictionary of atoms. Conversely, the synthesis of a new texture is performed by solving an optimization problem that seeks for a texture whose patches are sparse in the dictionary. This paper explores several strategies to choose this dictionary. A set of hand crafted dictionaries composed of edges, oscillations, lines or crossings elements allows to synthesize synthetic images with geometric features. Another option is to define the dictionary as the set of all the patches of an input exemplar. This leads to computer graphics methods for synthesis and shares some similarities with non-local means filtering. The last method we explore learns the dictionary by an optimization process that maximizes the sparsity of a set of exemplar patches. Applications of all these methods to texture synthesis, inpainting and classification shows the efficiency of the proposed texture model. This paper describes a model to capture the geometric structures of homogeneous textures. This model is based on a sparse expansion of the patches of the texture into a redundant dictionary. Classical texture synthesis methods are equivalent to a strict sparsity of s = 1 into the highly redundant dictionary of all the patches from some input exemplar. More refined models are learned by optimizing a dictionary that sparsify a set of input patches. Such a compressed representation can be tuned to achieve an increasing fidelity to the exemplar and is useful to perform texture mixing and texture classification.

O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O


Performance of data networks with random links We investigate simplified models of computer data networks and examine how the introduction of additional random links influences the performance of these networks. In general, the impact of additional random links on the performance of the network strongly depends on the routing algorithm used in the network. Significant performance gains can be achieved if the routing is based on "geometrical distance" or shortest path reduced table routing. With shortest path full table routing degradation of performance is observed. Models of computer data networks have attracted much attention in recent years. Generally, these models assume either regular topology of the network, in the form of a square lattice [1, 2, 7] or a binary Cayley tree [11] , or random graph topology [5] . On the other hand, it has been recently demonstrated that many technological, biological, and social networks are neither completely regular nor completely random, being somewhere between these two extremes [3] . Regular lattices rewired to introduce small amount of random connections, termed "small world networks", offer many advantages over purely regular or purely random topologies. In particular, models of dynamical systems based on "small world" lattices can often exhibit enhanced signal propagation capabilities, as observed in epidemic models or multi-player prisoners dilemma games played on such lattices [3] .. The purpose of this work is to investigate if a similar effect can be achieved in simple data network models, although our approach is different than the approach taken in [3] . We do not rewire the network, but rather examine how introduction of additional random links influences its performance. This is motivated by the question whether introduction of additional links can help to decongest an existing network. We found that the impact of additional random links on the performance of the network strongly depends on the routing scheme used in the network. Critical load of a network can be notably improved if the routing is based on a "geometrical distance". Adding small number of additional links can decrease the average delay and shift the transition to the jammed phase toward higher load values. This, in general, is not true for routing schemes based on the "shortest path metric". In this case, if the number of additional links is small, one can actually observe degradation of performance: many packets attempt to utilize shortcuts introduced by additional links, causing congestion which in effect pushes the network to a jammed phase. Reduced table routing can, to some extent, eliminate this problem. If packets located further than m links from the destination are routed randomly (other packets taking the shortest possible path), performance gains obtained by adding sufficient number of extra links can be quite significant.. In order to relate our findings to data network protocols used in practice, more research is clearly needed. In particular, congestion control mechanisms built into protocols such as TCP/IP will certainly affect phenomena reported here. This issue, as well as other possible modifications of the model, is currently under investigation. Furthermore, the authors believe that some of the issues raised in [10] , related to self-similar traffic modeling and analysis, and performance modeling of modern high-speed networks can be addressed by the methodology of this paper.

O O O O O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O