Android hybrid applications use the Web Kit engine on Android platform to render Web contents and process JavaScript codes, and enable JavaScript codes to access device sensitive resources and native APIs. Therefore, hybrid applications will bring different security issues compared to native applications. The existing privacy leak detection methods for Android native applications cannot be directly applied to hybrid applications. In addition to the Dalvik Virtual Machine (DVM), hybrid applications may also spread privacy in the WebView component, which increases the scope of privacy dissemination and increases the difficulty of taint tracking. We delve into the different characteristics of privacy spreading on the DVM, Webkit engine and JavaScript engine of hybrid ap-plications. We propose HTDroid, an efficient dynamic taint tracking system for hybrid applications. The core idea of HTDroid is to spread the taint tags in the DVM to the Web Kit engine, and add the function of tracking the spread of taint data to WebKit engine and JavaScript engine through source code instrumentation. Our experiments show that HTDroid can run on both Android emulators and devices and effectively detect privacy leaks in hybrid applications and can deal with the two ways of privacy leaks in hybrid applications while existing TaintDroid cannot. Compared to the original Android system, HTDroid incurs only 22% performance overhead on CaffenieMark benchmark and impose 4.3 % overhead on J avaScript V8 engine benchmark, which is acceptable for run-time taint tracking.

Word sense disambiguation is a challenging task that aims to distinguish the correct sense for a target word. Unlike typical methods which only use the context information, we present the basic idea that incorporates the global sense distribution and contextual sense dependency to determine the correct sense. In this paper, we leverage the generative process of the sequence topic model to model the sense distribution from the whole global corpus directly. Since contextual sense dependency is more likely to happen between successive words, we hypothesize that the sense assignment of the target word depends on the sense of the previous word. Hence, the sense dependency could be modeled by the probabilistic topic model with hidden Markov chain assumption. Furthermore, the information in the sense inventory of WordNet is used as prior knowledge for obtaining the non-uniform sense distribution over words. It is notable that the prior knowledge contributes to parameter learning and inference during the Gibbs Sampling procedure, hence we call the proposed method a knowledge-based unsupervised approach. We evaluate the proposed method on Senseval-2, Senseval-3, SemEval-2007, SemEval-2013, and SemEval-2015 English All-Word WSD datasets and the experimental results show that although the performance of the proposed method is restricted by the sparse problem, it still achieves comparable performance compared with the state-of-the-art knowledge-based approaches.

When expressing sentiment towards products, customers often explicitly indicate their recommendation status. Nevertheless, most existing literature focuses on sentiment analysis but neglects the rich correlation information that may be brought by explicit recommendation classification. We argue that the two tasks are correlated and hence, the knowledge in explicit recommendation classification can also be beneficial to sentiment analysis. Consequently, in this paper, a novel bidirectional encoder representations from transformers (BERT)-enhanced multi-task learning (BeMTL) approach is proposed to improve sentiment analysis with explicit recommendation classification. Specifically, the proposed MTL approach takes contextualized word embeddings produced by the pre-trained BERT-based embedding layer. Then, it learns the sentence contextual features shared between both tasks with a convolutional multi-head attention neural network. To fully exploit the correlation information between sentiment analysis and explicit recommendation classification tasks, a novel inter-task matching layer (IML) is designed to match their representations. In nutshell, our study reveals the potential of multi-task learning models on such types of problems, and experimental results on two Amazon datasets show that our approach outperforms the state-of-the-art baseline approaches for sentiment analysis.

In the real-world social networks, hashtags are widely applied for understanding the content of an individual microblog. However, users do not always take the initiative in attaching hashtags when posting a microblog so that much effort has been invested for automatically hashtag recommendation. As a new trend, users no longer only post texts but prefer to share with multimodal data, such as images. To deal with these situations, we propose an attention-based multimodal neural network model (AMNN) to learn the representations of multimodal microblogs and recommend relevant hashtags. In this article, we convert the hashtag recommendation task into a sequence generation problem. Then, we propose a hybrid neural network approach to extract the features of both texts and images and incorporate them into the sequence-to-sequence model for hashtag recommendation. Experimental results on the data set collected on Instagram and two public data sets demonstrate that the proposed method outperforms state-of-the-art methods. Our model achieves the best performance in three different metrics: precision, recall, and accuracy. The source code of this article can be obtained from “https://github.com/w5688414/AMNN.”

In recent years, the heterogeneous distributed platform integrating with FPGAs to accelerate computation tasks has been widely studied to deal with the deluge of data. However, most of current works suffer from poor universality and low resource utilization that run specific algorithms with the highly customized structure. Moreover, there are still many challenges, such as data curation, task scheduling, and resource management, which further limit the scalability of a CPU-FPGA distributed platform. In this paper, we present HeteroYARN, an FPGA-accelerated heterogeneous architecture based on YARN platform, which provides resource management and programming support for computing-intensive applications using FPGAs. In particular, the HeteroYARN abstracts FPGA accelerators as general resources and provides programming APIs to utilize those accelerators easily. Our HeteroYARN simplifies the request and usage of FPGA resources to enhance the efficiency of the heterogeneous framework while maintaining previous workflow unchanged. Experimental results using two representative algorithms, K-means and Naive Bayes classifier, which are accelerated by FPGAs, demonstrate the usability of the HeteroYARN framework and show performance speedup improvement by 7.5x (K-means) and 2.3x (Naive Bayes) respectively compared to conventional CPU-only applications provided by Mahout.

Logistic regression (LR) is the most commonly used loss function in multi-label image classification. However, it suffers from class imbalance problem caused by the huge difference in quantity between positive and negative samples as well as between different classes. First, we find that feeding randomly generated noise samples into an LR classifier is an effective way to detect class imbalances, and further define an informative imbalance metric named inference tendency based on noise sample analysis. Second, we design an efficient moving average based method for calculating inference tendency, which can be easily done during training with negligible overhead. Third, two novel rectification methods called extremum shift (ES) and tendency constraint (TC) are designed to offset or constrain inference tendency in the loss function, and mitigate class imbalances significantly. Finally, comparative experiments with Resnet on Microsoft COCO, NUS-WIDE and DeepFashion demonstrate the effectiveness of inference tendency and the superiority of our approach over the baseline LR and several state-of-the-art alternatives.

Point-of-interest (POI) recommendation is one of the most important services in the rapid growing location-based social networks (LBSNs). Good POI recommendation can help people explore the locations they haven't visited but are interested in, and help merchants find their target users. Time-aware POI recommendation aims to recommend unvisited POIs for a given user at a specified time in a day. However, previous methods, such as user-based collaborative filtering, lack the mining of the features of POIs and the learning of abstract spatio-temporal interactions. In this paper, we propose a novel time-aware POI recommendation method named ST-RNet (Spatio-Temporal Recommender Network) to address these shortages. ST-RNet works in the following fashion. Firstly, we analyze the crucial features in LBSNs to alleviate data sparsity problem and further measure the similarities between POIs. For subsequent network training, we then construct the embedding matrices with same dimension for users and POIs by POI-based Collaborative Filtering (PCF). Furthermore, the positive and negative check-in records are fed into a novel recommender neural network (RNet) to learn the embedding matrix of times and the abstract interactions between users, POIs and times. Finally, ST-RNet recommends the unvisited POIs most likely to be visited to a given user at a given time. The experimental results on Foursquare real-world dataset show that ST-RNet is effective on time-aware POI recommendation task and is capable of analyzing the hidden patterns behind spatio-temporal interactions.

Session-based recommendation which aims to recommend the next item in an anonymous session for users, becomes one of the most popular tasks in recommendation area. Traditional methods such as matrix factorization and item-to-item perform very poorly because they only take into account the last click of the session and ignore the information of the whole click sequence. On the other hand, Recurrent Neural Network (RNN) based methods have performed excellently in session-based recommendation. However, they only consider the user's sequential behavior in the current session or only use cross-session information to track user's interests over time, whereas the user preference is not emphasized in cross-session. Therefore, in this work, we design a novel neural network framework for personalized session-based recommendation, named Dual Attentive Neural Network (DANN). DANN considers user's main purpose of current session and user's personalized preference of cross-session. Specifically, in DANN we exploit a user-level attention mechanism to model user's personalized preference and capture user's main purpose in the current session via a session-level attention mechanism. The experimental results on two real-world datasets show that our DANN model outperforms other baseline models. Furthermore, we find that DANN achieves improvement when modeling user personalized preferences, which shows the advantage of modeling user's preference and user's purpose simultaneously.

Predicting users' irregular trips in a short term period is one of the crucial tasks in the intelligent transportation system. With the prediction, the taxi requesting services, such as Didi Chuxing in China, can manage the transportation resources to offer better services. There are several different transportation scenes, such as commuting scene and entertainment scene. The origin and the destination of entertainment scene are more unsure than that of commuting scene, so both origin and destination should be predicted. Moreover, users' trips on Didi platform is only a part of their real life, so these transportation data are only few weak samples. To address these challenges, in this paper, we propose Taxi Demand Prediction (TDP) model in challenging entertainment scene based on heterogeneous graph embedding and deep neural predicting network. TDP aims to predict next possible trip edges that have not appeared in historical data for each user in entertainment scene. Experimental results on the real-world dataset show that TDP achieves significant improvements over the state-of-the-art methods.

Android usually employs the Secure Socket Layer (SSL) protocol to protect the user’s privacy in network transmission. However, developers may misuse SSL-related APIs, which would lead attackers to steal user’s privacy through man-in-the-middle attacks. Existing methods based on static decompiling technology to detect SSL security vulnerabilities of Android applications cannot cope with the increasingly common packed applications. Meanwhile, dynamic analysis approaches have the disadvantages of excessive resource consumption and time-consuming. In this paper, we propose a dynamic method to solve this issue based on our novel automatic traversal model. At first, we propose several new traversal strategies to optimize the widget tree according to the user interface (UI) types and the interface state similarity. Furthermore, we develop a more granular traversal model by refining the traversal level from the Activity component to the Widget and implement a heuristic depth-first traversal algorithm in combination with our customized traversal strategy. In addition, the man-in-the-middle agent plug-in is extended to implement real-time attack test and return the attack results. Based on the above ideas, we have implemented SSLDetecter, an efficient automated detection system of Android application SSL security vulnerability. We apply it on multiple devices in parallel to detect 2456 popular applications in several mainstream application markets and find that 424 applications are suffering from SSL security vulnerabilities. Compared with the existing system SMV-HUNTER, the time efficiency of our system increases by 38% and the average detection rate increases by 6.39 percentage points, with many types of SSL vulnerabilities detected.

Summary As social networks such as micro‐blogging sites rapidly grow, deciding whom to follow (followee recommendation) becomes a significantly important problem. Most existing works exclusively rely on two traditional factors: the proximity between two users in the network topology or the similarity of the user‐generated contents in the social network, disregarding the effect of users' following behaviors. The challenge of how to effectively combine these two factors remains largely open. Moreover, most research studies simply sort the scores to find top‐k users, which is time‐consuming, especially for large‐scale networks. In this paper, we propose the idea that “predict users' following behaviors by following behaviors themselves.” We consider a user's following to others as a normal process of dynamic and coherent behavior, and we model the potential propagation of the users' following behaviors. Furthermore, based on our previous research on top‐k selection problem, we propose an effective top‐k followee recommendation algorithm, called FRFB. FRFB has low complexity and high scalability and, moreover, good adaptability to real‐life dynamic social networks. We conduct extensive experiments, with two real social network data sets (Wiki and Twitter), which show that FRFB outperforms the well‐known topology‐based followee recommendation algorithms.

With the popularity of cloud computing, mobile devices can store/retrieve personal data from anywhere at any time. Consequently, the data security problem in mobile cloud becomes more and more severe and prevents further development of mobile cloud. There are substantial studies that have been conducted to improve the cloud security. However, most of them are not applicable for mobile cloud since mobile devices only have limited computing resources and power. Solutions with low computational overhead are in great need for mobile cloud applications. In this paper, we propose a lightweight data sharing scheme (LDSS) for mobile cloud computing. It adopts CP-ABE, an access control technology used in normal cloud environment, but changes the structure of access control tree to make it suitable for mobile cloud environments. LDSS moves a large portion of the computational intensive access control tree transformation in CP-ABE from mobile devices to external proxy servers. Furthermore, to reduce the user revocation cost, it introduces attribute description fields to implement lazy-revocation, which is a thorny issue in program based CP-ABE systems. The experimental results show that LDSS can effectively reduce the overhead on the mobile device side when users are sharing data in mobile cloud environments.

Sorting is a basic computational task in Computer Science. As a variant of the sorting problem, top-k selecting have been widely used. To our knowledge, on average, the state-of-the-art top-k selecting algorithm Partial Quicksort takes C(n, k) = 2(n+1)Hn+2n-6k+6-2(n+3-k)Hn+1-k comparisons and about C(n, k)/6 exchanges to select the largest k terms from n terms, where Hn denotes the n-th harmonic number. In this paper, a novel top-k algorithm called DC-Top-k is proposed by employing a divide-and-conquer strategy. By a theoretical analysis, the algorithm is proved to be competitive with the state-of-the-art top-k algorithm on the compare time, with a significant improvement on the exchange time. On average, DC-Top-k takes at most (2-1/k)n+O(klog2k) comparisons and O(klog2k) exchanges to select the largest k terms from n terms. The effectiveness of the proposed algorithm is verified by a number of experiments which show that DC-Top-k is 1-3 times faster than Partial Quicksort and, moreover, is notably stabler than the latter. With an increase of k, it is also significantly more efficient than Min-heap based top-k algorithm (U. S. Patent, 2012). In the end, DC-Top-k is naturally implemented in a parallel computing environment, and a better scalability than Partial Quicksort is also demonstrated by experiments.

With the rapid development of microblog, millions of Internet users share their opinions on different aspects of daily life. By analyzing and monitoring sentiment information extracting from tweets related to an important event, we are able to gain insights into variation trends of users’ sentiment. In this paper, we focus on extracting public sentiment of microblog emergencies. A subtopic-level opinion mining method is proposed based on two-phase optimization. Different subtopics of emergencies are extracted based on retweets. Opinion tweets are classified to different subtopics. The sentiment score of opinion holders is calculated. The above results are optimized based on users and endorsement interactions between users. Experimental results validate the effectiveness of the proposed method.

Summary Role mining was recently proposed to automatically find roles among user‐permission assignments using data mining technologies. However, the current studies about role mining mainly focus on how to find roles, without considering the constraints that are essentially required in role‐based access control systems. In this paper, we present a role mining algorithm with constraints, especially for the cardinality constraints. We illustrate it is essential for role mining to take cardinality constraints into account, and introduce the concepts of the cardinality constraints of roles and permissions. We further propose a role mining algorithm to generate roles based on these two kinds of cardinality constraints. The algorithm uses graph theory to model the role mining problem and maps the relation of two roles to the relation of graph elements. We set an optimization goal for role mining and employ graph optimization theory to find roles that satisfy the aforementioned cardinality constraints. We carry out the experiments to evaluate our approach. The experimental results demonstrate the rationality and effectiveness of the proposed algorithm. Copyright © 2015 John Wiley & Sons, Ltd.

Topic modeling has become a widely used tool for document management. However, there are few topic models distinguishing the importance of documents on different topics. In this paper, we propose a framework LIMTopic to incorporate link based importance into topic modeling. To instantiate the framework, RankTopic and HITSTopic are proposed by incorporating topical pagerank and topical HITS into topic modeling respectively. Specifically, ranking methods are first used to compute the topical importance of documents. Then, a generalized relation is built between link importance and topic modeling. We empirically show that LIMTopic converges after a small number of iterations in most experimental settings. The necessity of incorporating link importance into topic modeling is justified based on KL-Divergences between topic distributions converted from topical link importance and those computed by basic topic models. To investigate the document network summarization performance of topic models, we propose a novel measure called log-likelihood of ranking-integrated document-word matrix. Extensive experimental results show that LIMTopic performs better than baseline models in generalization performance, document clustering and classification, topic interpretability and document network summarization performance. Moreover, RankTopic has comparable performance with relational topic model (RTM) and HITSTopic performs much better than baseline models in document clustering and classification.

Recently, there are many approaches proposed for mining roles using automated technologies. However, it lacks a tool set that can be used to aid the application of role mining approaches and update role states. In this demonstration, we introduce a tool set, RMiner, which is based on the core of WEKA, an open source data mining tool. RMiner implements most of the classic and latest role mining algorithms and provides interactive tools for administrator to update role states. The running examples of RMiner are presented to demonstrate the effectiveness of the tool set.

Large-scale search engines use hard disk drives (HDD) to store the mass index data for their capacity, whose performances are limited by the relatively low I/O performance of HDD. Caching is an effective optimization, and many caching algorithms have been proposed to improve retrieval performance. Considering the high cost of memory and huge amounts of data, the limited capacity of cache in memory cannot resolve the above problem thoroughly. In this paper, we adopt a solid state disk (SSD) based storage architecture, which uses SSD as a secondary cache for memory. We analyze the I/O patterns of search engines and propose SSD-based data management policies based on the hybrid storage architecture, including data selection, data placement and data replacement. Our main goal is to improve the performance of search engines while reducing operation cost inside SSD. The experimental results demonstrate the proposed architecture improves the hit ratio by 13.31%, the performance by 41.05%, the average access time inside SSD by 43.83%, and reduces block erasure operations by 71.52%.

The cipher text-based full-text retrieval technology is proposed to satisfy the pressing demands for high security in massive information sharing applications. Based on the analysis of general technology of full-text indexing, we propose an improved index structure that supports cipher text indexing and retrieval. Then we present approaches to construct, maintain and retrieve cipher text indexes. Meanwhile, we implement a cipher text-based full-text retrieval system, which allows full-text search on the encrypted documents in multiple formats without decryption. Finally, we carry out the experiments and evaluate the performance of cipher text index construction and retrieval.

As an important part of searching result presentation, query-biased document snippet generation has become a popular method of search engines that makes the result list more informative to users. Generating a single snippet is a lightweight task. However, it will be a heavy workload to generate multiple snippets of multiple documents as the search engines need to process large amount of queries per second, and each result list usually contains several snippets. To deal with this heavy workload, we propose a new high-performance snippet generation approach based on CPU-GPU hybrid system. Our main contribution of this paper is to present a parallel processing stream for large-scale snippet generation tasks using GPU. We adopt a sliding document segmentation method in our approach which costs more computing resources but can avoid the common defect that the high relevant fragment may be cut off. The experimental results show that our approach gains a speedup of nearly 6 times in average process time compared with the baseline approach-Highlighter.

In order to access sensitive documents shared over government, army and enterprise intranets, users rely on an indexing facility where they can quickly locate relevant documents they are allowed to access, (1) without leaking information about the remaining documents, (2) without imposing large load

Social tagging is an increasingly popular way to describe and classify documents on the web. However, the quality of the tags varies considerably since the tags are authored freely. How to rate the tags becomes an important issue. In this paper, we propose a topic-sensitive tag ranking (TSTR) approach to rate the tags on the web. We employ a generative probabilistic model to associate each tag with a distribution of topics. Then we construct a tag graph according to the co-tag relationships and perform a topic-level random walk over the graph to suggest a ranking score for each tag at different topics. Experimental results validate the effectiveness of the proposed tag ranking approach.