23,258 research outputs found
TAPER: query-aware, partition-enhancement for large, heterogenous, graphs
Graph partitioning has long been seen as a viable approach to address Graph
DBMS scalability. A partitioning, however, may introduce extra query processing
latency unless it is sensitive to a specific query workload, and optimised to
minimise inter-partition traversals for that workload. Additionally, it should
also be possible to incrementally adjust the partitioning in reaction to
changes in the graph topology, the query workload, or both. Because of their
complexity, current partitioning algorithms fall short of one or both of these
requirements, as they are designed for offline use and as one-off operations.
The TAPER system aims to address both requirements, whilst leveraging existing
partitioning algorithms. TAPER takes any given initial partitioning as a
starting point, and iteratively adjusts it by swapping chosen vertices across
partitions, heuristically reducing the probability of inter-partition
traversals for a given pattern matching queries workload. Iterations are
inexpensive thanks to time and space optimisations in the underlying support
data structures. We evaluate TAPER on two different large test graphs and over
realistic query workloads. Our results indicate that, given a hash-based
partitioning, TAPER reduces the number of inter-partition traversals by around
80%; given an unweighted METIS partitioning, by around 30%. These reductions
are achieved within 8 iterations and with the additional advantage of being
workload-aware and usable online.Comment: 12 pages, 11 figures, unpublishe
Deep Lesion Graphs in the Wild: Relationship Learning and Organization of Significant Radiology Image Findings in a Diverse Large-scale Lesion Database
Radiologists in their daily work routinely find and annotate significant
abnormalities on a large number of radiology images. Such abnormalities, or
lesions, have collected over years and stored in hospitals' picture archiving
and communication systems. However, they are basically unsorted and lack
semantic annotations like type and location. In this paper, we aim to organize
and explore them by learning a deep feature representation for each lesion. A
large-scale and comprehensive dataset, DeepLesion, is introduced for this task.
DeepLesion contains bounding boxes and size measurements of over 32K lesions.
To model their similarity relationship, we leverage multiple supervision
information including types, self-supervised location coordinates and sizes.
They require little manual annotation effort but describe useful attributes of
the lesions. Then, a triplet network is utilized to learn lesion embeddings
with a sequential sampling strategy to depict their hierarchical similarity
structure. Experiments show promising qualitative and quantitative results on
lesion retrieval, clustering, and classification. The learned embeddings can be
further employed to build a lesion graph for various clinically useful
applications. We propose algorithms for intra-patient lesion matching and
missing annotation mining. Experimental results validate their effectiveness.Comment: Accepted by CVPR2018. DeepLesion url adde
Efficient Diversification of Web Search Results
In this paper we analyze the efficiency of various search results
diversification methods. While efficacy of diversification approaches has been
deeply investigated in the past, response time and scalability issues have been
rarely addressed. A unified framework for studying performance and feasibility
of result diversification solutions is thus proposed. First we define a new
methodology for detecting when, and how, query results need to be diversified.
To this purpose, we rely on the concept of "query refinement" to estimate the
probability of a query to be ambiguous. Then, relying on this novel ambiguity
detection method, we deploy and compare on a standard test set, three different
diversification methods: IASelect, xQuAD, and OptSelect. While the first two
are recent state-of-the-art proposals, the latter is an original algorithm
introduced in this paper. We evaluate both the efficiency and the effectiveness
of our approach against its competitors by using the standard TREC Web
diversification track testbed. Results shown that OptSelect is able to run two
orders of magnitude faster than the two other state-of-the-art approaches and
to obtain comparable figures in diversification effectiveness.Comment: VLDB201
Learning a Deep Listwise Context Model for Ranking Refinement
Learning to rank has been intensively studied and widely applied in
information retrieval. Typically, a global ranking function is learned from a
set of labeled data, which can achieve good performance on average but may be
suboptimal for individual queries by ignoring the fact that relevant documents
for different queries may have different distributions in the feature space.
Inspired by the idea of pseudo relevance feedback where top ranked documents,
which we refer as the \textit{local ranking context}, can provide important
information about the query's characteristics, we propose to use the inherent
feature distributions of the top results to learn a Deep Listwise Context Model
that helps us fine tune the initial ranked list. Specifically, we employ a
recurrent neural network to sequentially encode the top results using their
feature vectors, learn a local context model and use it to re-rank the top
results. There are three merits with our model: (1) Our model can capture the
local ranking context based on the complex interactions between top results
using a deep neural network; (2) Our model can be built upon existing
learning-to-rank methods by directly using their extracted feature vectors; (3)
Our model is trained with an attention-based loss function, which is more
effective and efficient than many existing listwise methods. Experimental
results show that the proposed model can significantly improve the
state-of-the-art learning to rank methods on benchmark retrieval corpora
Recommended from our members
Semantic Concept Co-Occurrence Patterns for Image Annotation and Retrieval.
Describing visual image contents by semantic concepts is an effective and straightforward way to facilitate various high level applications. Inferring semantic concepts from low-level pictorial feature analysis is challenging due to the semantic gap problem, while manually labeling concepts is unwise because of a large number of images in both online and offline collections. In this paper, we present a novel approach to automatically generate intermediate image descriptors by exploiting concept co-occurrence patterns in the pre-labeled training set that renders it possible to depict complex scene images semantically. Our work is motivated by the fact that multiple concepts that frequently co-occur across images form patterns which could provide contextual cues for individual concept inference. We discover the co-occurrence patterns as hierarchical communities by graph modularity maximization in a network with nodes and edges representing concepts and co-occurrence relationships separately. A random walk process working on the inferred concept probabilities with the discovered co-occurrence patterns is applied to acquire the refined concept signature representation. Through experiments in automatic image annotation and semantic image retrieval on several challenging datasets, we demonstrate the effectiveness of the proposed concept co-occurrence patterns as well as the concept signature representation in comparison with state-of-the-art approaches
- …