We study the problem of detecting sentences describing adverse drug reactions (ADRs) and frame the problem as binary classification. We investigate different neural network (NN) architectures for ADR classification. In particular, we propose two new neural network models, Convolutional Recurrent Neural Network (CRNN) by concatenating convolutional neural networks with recurrent neural networks, and Convolutional Neural Network with Attention (CNNA) by adding attention weights into convolutional neural networks. We evaluate various NN architectures on a Twitter dataset containing informal language and an Adverse Drug Effects (ADE) dataset constructed by sampling from MEDLINE case reports. Experimental results show that all the NN architectures outperform the traditional maximum entropy classifiers trained from n-grams with different weighting strategies considerably on both datasets. On the Twitter dataset, all the NN architectures perform similarly. But on the ADE dataset, CNN performs better than other more complex CNN variants. Nevertheless, CNNA allows the visualisation of attention weights of words when making classification decisions and hence is more appropriate for the extraction of word subsequences describing ADRs.

The objective of this special issue is to report on recent trends in digital and media technologies responding to the challenges of managing and accessing multimedia (images, audio, video, 3D/4D material, etc.).In a highly selective review procedure we accepted contributions describing recent work that aims at narrowing the large disparity between the low-level multimedia descriptors and the richness of subjectivity of semantics in user queries and human interpretations of audiovisual data.The articles in this special issue can be grouped into following categories: Multimedia Analysis (Section 1), Multimedia Ontologies and Data Integration (Section 2), and Social Media and Retrieval (Section 3).

Sentiment analysis or opinion mining aims to use automated tools to detect subjective information such as opinions, attitudes, and feelings expressed in text. This paper proposes a novel probabilistic modeling framework called joint sentiment-topic (JST) model based on latent Dirichlet allocation (LDA), which detects sentiment and topic simultaneously from text. A reparameterized version of the JST model called Reverse-JST, obtained by reversing the sequence of sentiment and topic generation in the modeling process, is also studied. Although JST is equivalent to Reverse-JST without a hierarchical prior, extensive experiments show that when sentiment priors are added, JST performs consistently better than Reverse-JST. Besides, unlike supervised approaches to sentiment classification which often fail to produce satisfactory performance when shifting to other domains, the weakly supervised nature of JST makes it highly portable to other domains. This is verified by the experimental results on data sets from five different domains where the JST model even outperforms existing semi-supervised approaches in some of the data sets despite using no labeled documents. Moreover, the topics and topic sentiment detected by JST are indeed coherent and informative. We hypothesize that the JST model can readily meet the demand of large-scale sentiment analysis from the web in an open-ended fashion.

This tutorial is concerned with creating the best possible multimedia search experience. The intriguing bit here is that the query itself can be a multimedia excerpt: For example, when you walk around in an unknown place and stumble across an interesting landmark, would it not be great if you could just take a picture with your mobile phone and send it to a service that finds a similar picture in a database and tells you more about the building - and about its significance for that matter?

This article is set in the context of searching text and image repositories by keyword. We develop a unified probabilistic framework for text, image, and combined text and image retrieval that is based on the detection of keywords (concepts) using automated image annotation technology. Our framework is deeply rooted in information theory and lends itself to use with other media types. We estimate a statistical model in a multimodal feature space for each possible query keyword. The key element of our framework is to identify feature space transformations that make them comparable in complexity and density. We select the optimal multimodal feature space with a minimum description length criterion from a set of candidate feature spaces that are computed with the average-mutual-information criterion for the text part and hierarchical expectation maximization for the visual part of the data. We evaluate our approach in three retrieval experiments (only text retrieval, only image retrieval, and text combined with image retrieval), verify the framework's low computational complexity, and compare with existing state-of-the-art ad-hoc models.

This paper describes an evaluation of a number of subsets of features for the purpose of image annotation using a non-parametric density estimation algorithm (described in). By applying some general recommendations from the literature and through evaluating a range of low-level visual feature configurations and subsets, we achieve an improvement in performance, measured by the mean average precision, from 0.2861 to 0.3800. We demonstrate the significant impact that the choice of visual or low-level features can have on an automatic image annotation system. There is often a large set of possible features that may be used and a corresponding large number of variables that can be configured or tuned for each feature in addition to other options for the annotation approach. Judicious and effective selection of features for image annotation is required to achieve the best performance with the least user design effort. We discuss the performance of the chosen feature subsets in comparison with previous results and propose some general recommendations observed from the work so far.

Abstract Expert finding is a key task in enterprise search and has recently attracted lots of attention from both research and industry communities. Given a search topic, a prominent existing approach is to apply some information retrieval (IR) system to retrieve top ranking documents, which will then be used to derive associations between experts and the search topic based on cooccurrences. However, we argue that expert finding is more sensitive to multiple levels of associations and document features that current expert finding systems insufficiently address, including (a) multiple levels of associations between experts and search topics, (b) document internal structure, and (c) document authority. We propose a novel approach that integrates the above‐mentioned three aspects as well as a query expansion technique in a two‐stage model for expert finding. A systematic evaluation is conducted on TREC collections to test the performance of our approach as well as the effects of multiple windows, document features, and query expansion. These experimental results show that query expansion can dramatically improve expert finding performance with statistical significance. For three well‐known IR models with or without query expansion, document internal structures help improve a single window‐based approach but without statistical significance, while our novel multiple window‐based approach can significantly improve the performance of a single window‐based approach both with and without document internal structures.

We argue that expert finding is sensitive to multiple document features in an organization, and therefore, can benefit from the incorporation of these document features. We propose a unified language model, which integrates multiple document features, namely, multiple levels of associations, PageRank, indegree, internal document structure, and URL length. Our experiments on two TREC Enterprise Track collections, i.e., the W3C and CSIRO datasets, demonstrate that the natures of the two organizational intranets and two types of expert finding tasks, i.e., key contact finding for CSIRO and knowledgeable person finding for W3C, influence the effectiveness of different document features. Our work provides insights into which document features work for certain types of expert finding tasks, and helps design expert finding strategies that are effective for different scenarios.

Dissimilarity measurement plays a crucial role in content-based image retrieval. In this paper, 16 core dissimilarity measures are introduced and evaluated. We carry out a systematic performance comparison on three image collections, Corel, Getty and Trecvid2003, with 7 different feature spaces. Two search scenarios are considered: single image queries based on the vector space model, and multi-image queries based on k-nearest neighbours search. A number of observations are drawn, which will lay a foundation for developing more effective image search technologies.

The International Workshop on Recommendation and Collaboration (ReColl 2008) aims to identify emerging trends in recommendation technology and collaborative environments in the context of intelligent user interfaces. We explore these two topics separately and the synergies between them.

Content-based image similarity search plays a key role in multimedia retrieval. Each image is usually represented as a point in a high-dimensional feature space. The key challenge of searching similar images from a large database is the high computational overhead due to the "curse of dimensionality". Reducing the dimensionality is an important means to tackle the problem. In this paper, we study dimensionality reduction for top-k image retrieval. Intuitively, an effective dimensionality reduction method should not only preserve the close locations of similar images (or points), but also separate those dissimilar ones far apart in the reduced subspace. Existing dimensionality reduction methods mainly focused on the former. We propose a novel idea called Locality Condensation (LC) to not only preserve localities determined by neighborhood information and their global similarity relationship, but also ensure that different localities will not invade each other in the low-dimensional subspace. To generate non-overlapping localities in the subspace, LC first performs an elliptical condensation, which condenses each locality with an elliptical shape into a more compact hypersphere to enlarge the margins among different localities and estimate the projection in the subspace for overlap analysis. Through a convex optimization, LC further performs a scaling condensation on the obtained hyperspheres based on their projections in the subspace with minimal condensation degrees. By condensing the localities effectively, the potential overlaps among different localities in the low-dimensional subspace are prevented. Consequently, for similarity search in the subspace, the number of false hits (i.e., distant points that are falsely retrieved) will be reduced. Extensive experimental comparisons with existing methods demonstrate the superiority of our proposal.

We address the problem of searching multimedia by semantic similarity in a keyword space. In contrast to previous research we represent multimedia content by a vector of keywords instead of a vector of low-level features. This vector of keywords can be obtained through user manual annotations or computed by an automatic annotation algorithm. In this setting, we studied the influence of two aspects of the search by semantic similarity process: (1) accuracy of user keywords versus automatic keywords and (2) functions to compute semantic similarity between keyword vectors of two multimedia documents. We consider these two aspects to be crucial in the design of a keyword space that can exploit social-media information and can enrich applications such as Flickr and YouTube. Experiments were performed on an image and a video dataset with a large number of keywords, with different similarity functions and with two annotation methods. Surprisingly, we found that multimedia semantic similarity with automatic keywords performs as good as or better than 95% accurate user keywords.

This paper describes the generation of a model capturing information on how placenames co‐occur together. The advantages of the co‐occurrence model over traditional gazetteers are discussed and the problem of placename disambiguation is presented as a case study. We begin by outlining the problem of ambiguous placenames. We demonstrate how analysis of Wikipedia can be used in the generation of a co‐occurrence model. The accuracy of our model is compared to a handcrafted ground truth; then we evaluate alternative methods of applying this model to the disambiguation of placenames in free text (using the GeoCLEF evaluation forum). We conclude by showing how the inclusion of placenames in both the text and geographic parts of a query provides the maximum mean average precision and outline the benefits of a co‐occurrence model as a data source for the wider field of geographic information retrieval (GIR).

Dimensionality reduction plays an important role in efficient similarity search, which is often based on k-nearest neighbor (k-NN) queries over a high-dimensional feature space. In this paper, we introduce a novel type of k-NN query, namely conditional k-NN (ck-NN), which considers dimension-specific constraint in addition to the inter-point distances. However, existing dimensionality reduction methods are not applicable to this new type of queries. We propose a novel Mean-Std (standard deviation) guided Dimensionality Reduction (MSDR) to support a pruning based efficient ck-NN query processing strategy. Our preliminary experimental results on 3D protein structure data demonstrate that the MSDR method is promising.

In this paper we formulate image retrieval by text query as a vector space classification problem. This is achieved by creating a high-dimensional visual vocabulary that represents the image documents in great detail. We show how the representation of these image documents enables the application of well known text retrieval techniques such as Rocchio tf-idf and naíve Bayes to the semantic image retrieval problem. We tested these methods on a Corel images subset and achieve state-of-the-art retrieval performance using the proposed methods.

This paper outlines a system for searching and browsing 1.14 million images from the World Wide Web (WWW) based on their visual content. At the heart of the system lies an automatically constructed network of images that can be navigated quickly by following its edges. The browsing experience is enhanced in a number of ways including multidimensional scaling of the graph neighbourhood for display purposes, Markov clustering of the image network to provide summaries of its content, and automated annotation of the images to allow users to access the network through text queries.

We propose a novel algorithm for extracting information by mining the feature space clusters and then assigning salient concepts to them. Bayesian techniques for extracting concepts from multimedia usually suffer either from lack of data or from too complex concepts to be represented by a single statistical model. An incremental information extraction approach, working at different levels of abstraction, would be able to handle concepts of varying complexities. We present the results of our research on the initial part of an incremental approach, the extraction of the most salient concepts from multimedia information.

The paper reports on experimental results obtained from a performance comparison of feature combinations strategies in content based image retrieval. The use of support vector machines is compared to CombMIN, CombMAX, CombSUM and BordaFuse combination strategies, all of which are evaluated on a carefully compiled set of Corel images and the TRECVID 2003 search task collection.

We present three new visualization front-ends that aid navigation through the set of documents returned by a search engine (hit documents). We cluster the hit documents to visually group these documents and label the groups with related words. The different front-ends cater for different user needs, but all can browse cluster information as well as drilling up or down in one or more clusters and refining the search using one or more of the suggested related keywords.