IBM

About: IBM is a company organization based out in Armonk, New York, United States. It is known for research contribution in the topics: Layer (electronics) & Cache. The organization has 134567 authors who have published 253905 publications receiving 7458795 citations. The organization is also known as: International Business Machines Corporation & Big Blue.

Privacy preserving mining of association rules

Abstract: We present a framework for mining association rules from transactions consisting of categorical items where the data has been randomized to preserve privacy of individual transactions. While it is feasible to recover association rules and preserve privacy using a straightforward "uniform" randomization, the discovered rules can unfortunately be exploited to find privacy breaches. We analyze the nature of privacy breaches and propose a class of randomization operators that are much more effective than uniform randomization in limiting the breaches. We derive formulae for an unbiased support estimator and its variance, which allow us to recover itemset supports from randomized datasets, and show how to incorporate these formulae into mining algorithms. Finally, we present experimental results that validate the algorithm by applying it on real datasets.

Dynamic Placement of Virtual Machines for Managing SLA Violations

Abstract: A dynamic server migration and consolidation algorithm is introduced. The algorithm is shown to provide substantial improvement over static server consolidation in reducing the amount of required capacity and the rate of service level agreement violations. Benefits accrue for workloads that are variable and can be forecast over intervals shorter than the time scale of demand variability. The management algorithm reduces the amount of physical capacity required to support a specified rate of SLA violations for a given workload by as much as 50% as compared to static consolidation approach. Another result is that the rate of SLA violations at fixed capacity may be reduced by up to 20%. The results are based on hundreds of production workload traces across a variety of operating systems, applications, and industries.

Optimal aggregation algorithms for middleware

Abstract: Assume that each object in a database has m grades, or scores, one for each of m attributes. For example, an object can have a color grade, that tells how red it is, and a shape grade, that tells how round it is. For each attribute, there is a sorted list, which lists each object and its grade under that attribute, sorted by grade (highest grade first). There is some monotone aggregation function, or combining rule, such as min or average, that combines the individual grades to obtain an overall grade.To determine objects that have the best overall grades, the naive algorithm must access every object in the database, to find its grade under each attribute. Fagin has given an algorithm (“Fagin's Algorithm”, or FA) that is much more efficient. For some distributions on grades, and for some monotone aggregation functions, FA is optimal in a high-probability sense.We analyze an elegant and remarkably simple algorithm (“the threshold algorithm”, or TA) that is optimal in a much stronger sense than FA. We show that TA is essentially optimal, not just for some monotone aggregation functions, but for all of them, and not just in a high-probability sense, but over every database. Unlike FA, which requires large buffers (whose size may grow unboundedly as the database size grows), TA requires only a small, constant-size buffer.We distinguish two types of access: sorted access (where the middleware system obtains the grade of an object in some sorted list by proceeding through the list sequentially from the top), and random access (where the middleware system requests the grade of object in a list, and obtains it in one step). We consider the scenarios where random access is either impossible, or expensive relative to sorted access, and provide algorithms that are essentially optimal for these cases as well.

Revisiting the factor structure of the system usability scale

Abstract: In 2009, we published a paper in which we showed how three independent sources of data indicated that, rather than being a unidimensional measure of perceived usability, the System Usability Scale apparently had two factors: Usability (all items except 4 and 10) and Learnability (Items 4 and 10). In that paper, we called for other researchers to report attempts to replicate that finding. The published research since 2009 has consistently failed to replicate that factor structure. In this paper, we report an analysis of over 9,000 completed SUS questionnaires that shows that the SUS is indeed bidimensional, but not in any interesting or useful way. A comparison of the fit of three confirmatory factor analyses showed that a model in which the SUS's positive-tone (odd-numbered) and negative-tone (even-numbered) were aligned with two factors had a better fit than a unidimensional model (all items on one factor) or the Usability/Learnability model we published in 2009. Because a distinction based on item tone is of little practical or theoretical interest, we recommend that user experience practitioners and researchers treat the SUS as a unidimensional measure of perceived usability, and no longer routinely compute Usability and Learnability subscales.

Fisher information and stochastic complexity

Abstract: By taking into account the Fisher information and removing an inherent redundancy in earlier two-part codes, a sharper code length as the stochastic complexity and the associated universal process are derived for a class of parametric processes. The main condition required is that the maximum-likelihood estimates satisfy the central limit theorem. The same code length is also obtained from the so-called maximum-likelihood code.