6,043 research outputs found
Graph Summarization
The continuous and rapid growth of highly interconnected datasets, which are
both voluminous and complex, calls for the development of adequate processing
and analytical techniques. One method for condensing and simplifying such
datasets is graph summarization. It denotes a series of application-specific
algorithms designed to transform graphs into more compact representations while
preserving structural patterns, query answers, or specific property
distributions. As this problem is common to several areas studying graph
topologies, different approaches, such as clustering, compression, sampling, or
influence detection, have been proposed, primarily based on statistical and
optimization methods. The focus of our chapter is to pinpoint the main graph
summarization methods, but especially to focus on the most recent approaches
and novel research trends on this topic, not yet covered by previous surveys.Comment: To appear in the Encyclopedia of Big Data Technologie
The ABACOC Algorithm: a Novel Approach for Nonparametric Classification of Data Streams
Stream mining poses unique challenges to machine learning: predictive models
are required to be scalable, incrementally trainable, must remain bounded in
size (even when the data stream is arbitrarily long), and be nonparametric in
order to achieve high accuracy even in complex and dynamic environments.
Moreover, the learning system must be parameterless ---traditional tuning
methods are problematic in streaming settings--- and avoid requiring prior
knowledge of the number of distinct class labels occurring in the stream. In
this paper, we introduce a new algorithmic approach for nonparametric learning
in data streams. Our approach addresses all above mentioned challenges by
learning a model that covers the input space using simple local classifiers.
The distribution of these classifiers dynamically adapts to the local (unknown)
complexity of the classification problem, thus achieving a good balance between
model complexity and predictive accuracy. We design four variants of our
approach of increasing adaptivity. By means of an extensive empirical
evaluation against standard nonparametric baselines, we show state-of-the-art
results in terms of accuracy versus model size. For the variant that imposes a
strict bound on the model size, we show better performance against all other
methods measured at the same model size value. Our empirical analysis is
complemented by a theoretical performance guarantee which does not rely on any
stochastic assumption on the source generating the stream
Scalable Teacher Forcing Network for Semi-Supervised Large Scale Data Streams
The large-scale data stream problem refers to high-speed information flow
which cannot be processed in scalable manner under a traditional computing
platform. This problem also imposes expensive labelling cost making the
deployment of fully supervised algorithms unfeasible. On the other hand, the
problem of semi-supervised large-scale data streams is little explored in the
literature because most works are designed in the traditional single-node
computing environments while also being fully supervised approaches. This paper
offers Weakly Supervised Scalable Teacher Forcing Network (WeScatterNet) to
cope with the scarcity of labelled samples and the large-scale data streams
simultaneously. WeScatterNet is crafted under distributed computing platform of
Apache Spark with a data-free model fusion strategy for model compression after
parallel computing stage. It features an open network structure to address the
global and local drift problems while integrating a data augmentation,
annotation and auto-correction () method for handling partially labelled
data streams. The performance of WeScatterNet is numerically evaluated in the
six large-scale data stream problems with only label proportions. It
shows highly competitive performance even if compared with fully supervised
learners with label proportions.Comment: This paper has been accepted for publication in Information Science
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