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A novel model for trajectories and semantic regions (sest-hiHMM) is proposed.A sticky version of sest-hiHMMs is proposed for reducing redundant semantic regions.An extended definition of semantic regions covers actual regions, not sets of points.Our models concern the temporal dependency of observations in a trajectory.Our models retrieve reasonable semantic regions from a real trajectory dataset. With an increasing attempt of finding latent semantics in a video dataset, trajectories have become key components since they intrinsically include concise characteristics of object movements. An approach to analyze a trajectory dataset has concentrated on semantic region retrieval, which extracts some regions in which have their own patterns of object movements. Semantic region retrieval has become an important topic since the semantic regions are useful for various applications, such as activity analysis. The previous literatures, however, have just revealed semantically relevant points, rather than actual regions, and have less consideration of temporal dependency of observations in a trajectory. In this paper, we propose a novel model for trajectory analysis and semantic region retrieval. We first extend the meaning of semantic regions that can cover actual regions. We build a model for the extended semantic regions based on a hierarchically linked infinite hidden Markov model, which can capture the temporal dependency between adjacent observations, and retrieve the semantic regions from a trajectory dataset. In addition, we propose a sticky extension to diminish redundant semantic regions that occur in a non-sticky model. The experimental results demonstrate that our models well extract semantic regions from a real trajectory dataset.

Text categorization has gained increasing popularity in the last years due the explosive growth of multimedia documents. As a document can be associated with multiple non-exclusive categories simultaneously (e.g., Virus, Health, Sports, and Olympic Games), text categorization provides many opportunities for developing novel multi-label learning approaches devoted specifically to textual data. In this paper, we propose an ensemble multi-label classification method for text categorization based on four key ideas: (1) performing Latent Semantic Indexing based on distinct orthogonal projections on lower-dimensional spaces of concepts; (2) random splitting of the vocabulary; (3) document bootstrapping; and (4) the use of BoosTexter as a powerful multi-label base learner for text categorization to simultaneously encourage diversity and individual accuracy in the committee. Diversity of the ensemble is promoted through random splits of the vocabulary that leads to different orthogonal projections on lower-dimensional latent concept spaces. Accuracy of the committee members is promoted through the underlying latent semantic structure uncovered in the text. The combination of both rotation-based ensemble construction and Latent Semantic Indexing projection is shown to bring about significant improvements in terms of Average Precision, Coverage, Ranking loss and One error compared to five state-of-the-art approaches across 14 real-word textual data sets covering a wide variety of topics including health, education, business, science and arts.

WOS: 000336872300023, In this paper, genetic algorithm oriented latent semantic features (GALSF) are proposed to obtain better representation of documents in text classification. The proposed approach consists of feature selection and feature transformation stages. The first stage is carried out using the state-of-the-art filter-based methods. The second stage employs latent semantic indexing (LSI) empowered by genetic algorithm such that a better projection is attained using appropriate singular vectors, which are not limited to the ones corresponding to the largest singular values, unlike standard LSI approach. In this way, the singular vectors with small singular values may also be used for projection whereas the vectors with large singular values may be eliminated as well to obtain better discrimination. Experimental results demonstrate that GALSF outperforms both LSI and filter-based feature selection methods on benchmark datasets for various feature dimensions

Research highlights? We adapted the Google similarity distance algorithm into a more efficient new algorithm. ? We used the PLSA to enhance the original 2-gram NGD into a 3-gram algorithm. ? To extract the most important sequence of keywords to provide the most relevant search results to the user. There have been many studies about how to help users enter more keywords into a search engine to find the most relevant documents or search results. Methods previously reported in the literature require a database to save the user profile, and construct a well-trained model to provide the potential "next keyword" to the user. Because the predictive models are based on the training data, they can only be used in a single knowledge domain. In this paper, we describe a new algorithm called "Google latent semantic distance" (GLSD) and use it to extract the most important sequence of keywords to provide the most relevant search results to the user. Our method utilizes on-line, real-time processing and needs no training data. Thus, it can be used in different knowledge domains. Our experiments show that the GLSD can achieve high accuracy, and we can find out the most relevant information in the top search results in most cases. We believe that this new system can increase users' effectiveness in both reading and writing articles.

Research highlights? This research takes advantages of corpus-based ontology and Information Retrieval technologies to evaluate the semantic similarity between irregular sentences. ? The part of speech concept was taken into account and was integrated into the proposed semantic-VSM measure. ? This research tries to qualify the semantic similarity of natural language sentences. A novel sentence similarity measure for semantic based expert systems is presented. The well-known problem in the fields of semantic processing, such as QA systems, is to evaluate the semantic similarity between irregular sentences. This paper takes advantage of corpus-based ontology to overcome this problem. A transformed vector space model is introduced in this article. The proposed two-phase algorithm evaluates the semantic similarity for two or more sentences via a semantic vector space. The first phase built part-of-speech (POS) based subspaces by the raw data, and the latter carried out a cosine evaluation and adopted the WordNet ontology to construct the semantic vectors. Unlike other related researches that focused only on short sentences, our algorithm is applicable to short (4-5 words), medium (8-12 words), and even long sentences (over 12 words). The experiment demonstrates that the proposed algorithm has outstanding performance in handling long sentences with complex syntax. The significance of this research lies in the semantic similarity extraction of sentences, with arbitrary structures.

Probabilistic latent semantic analysis (PLSA) is a double structure mixture model which has got a wide application in text and web mining. This method is capable of establishing hidden semantic relations among the observed features, using a number of latent variables. In this approach, the selection of the correct number of latent variables is critical. In the most of the previous researches, the number of latent topics was selected based on the number of invoked classes. This paper presents a method, based on backward elimination approach, which is capable of unsupervised order selection in PLSA. This method starts with a model having a number of components more than the needed value, and then prunes the mixtures to reach their optimum size. During the elimination process, proper selection of some latent variables which must be deleted is the most essential problem, and its relation to the final performance of the pruned model is straightforward. To treat this problem, we introduce a new combined pruning method which selects the best options for removal, while keeping a low computational cost, at all. We conducted some experiments on two datasets from Reuters-21578 corpus. The obtained results show that this algorithm leads to an optimized number of latent variables and in turn achieves better clustering performance compared to the conventional model selection methods. It also shows superiority over the case in which a PLSA model with a fixed number of latent variables, equal to the real number of clusters, is exploited.

Topics often transit among documents in a document collection. To improve the accuracy of the topic detection and tracking (TDT) algorithms in discovering topics or classifying documents, it is necessary to make full use of this kind of topic transition information. However, TDT algorithms usually find topics based on topic models, such as LDA, pLSI, etc., which are a kind of mixture model and make the topic transition difficult to be denoted and implemented. A topic transition model representation based on hidden Markov model is present, and learning the topic transition from documents is discussed. Based on the model, two TDT algorithms incorporating topic transition, i.e. topic discovering and document classifying, are provided to show the application of the proposed model. Experiments on two real-world document collections are done with the two algorithms, and performance comparison with other similar algorithm shows that the accuracy can achieve 93% for topic discovering in Reuters-21578, and 97.3% in document classifying. Furthermore, topic transition discovered by the algorithm on a dataset which was collected from a BBS website is consistent with the manual analysis results.

Traditional information retrieval method use keywords occurring in documents to determine the class of the documents, but usually retrieves unrelated web pages. In order to effectively classify web pages solving the synonymous keyword problem, we propose a web page classification based on support vector machine using a weighted vote schema for various features. The system uses both latent semantic analysis and web page feature selection training and recognition by the SVM model. Latent semantic analysis is used to find the semantic relations between keywords, and between documents. The latent semantic analysis method projects terms and a document into a vector space to find latent information in the document. At the same time, we also extract text features from web page content. Through text features, web pages are classified into a suitable category. These two features are sent to the SVM for training and testing respectively. Based on the output of the SVM, a voting schema is used to determine the category of the web page. Experimental results indicate our method is more effective than traditional methods.

In this paper, a new semantic learning method for content-based image retrieval using the analytic hierarchical process (AHP) is proposed. AHP proposed by Satty used a systematical way to solve multi-criteria preference problems involving qualitative data and was widely applied to a great diversity of areas. In general, the interpretations of an image are multiple and hard to describe in terms of low-level features due to the lack of a complete image understanding model. The AHP provides a good way to evaluate the fitness of a semantic description used to interpret an image. According to a predefined concept hierarchy, a semantic vector, consisting of the fitness values of semantic descriptions of a given image, is used to represent the semantic content of the image. Based on the semantic vectors, the database images are clustered. For each semantic cluster, the weightings of the low-level features (i.e. color, shape, and texture) used to represent the content of the images are calculated by analyzing the homogeneity of the class. In this paper, the values of weightings setting to the three low-level feature types are diverse in different semantic clusters for retrieval. The proposed semantic learning scheme provides a way to bridge the gap between the high-level semantic concept and the low-level features for content-based image retrieval. Experimental results show that the performance of the proposed method is excellent when compared with that of the traditional text-based semantic retrieval techniques and content-based image retrieval methods.