Web searchers frequently transition from desktop computers and laptops to mobile devices, and vice versa. Little is known about the nature of cross-device search tasks, yet they represent an important opportunity for search engines to help their users, especially those on the target (post-switch) device. For example, the search engine could save the current session and re-instate it post switch, or it could capitalize on down-time between devices to proactively re-trieve content on behalf of the searcher. In this paper, we present a log-based study to define and characterize cross-device search be-havior and predict the resumption of cross-device tasks. Using data from a large commercial search engine, we show that there are dis-cernible and noteworthy patterns of search behavior associated with device transitions. We also develop learned models for predicting task resumption on the target device using behavioral, topical, geo-spatial, and temporal features. Our findings show that our models can attain strong prediction accuracy and have direct implications for the development of tools to help people search more effectively in a multi-device world.

Latent topic analysis has emerged as one of the most effective methods for classifying, clustering and retrieving textual data. However, existing models such as Latent Dirichlet Allocation (LDA) were developed for static corpora of relatively large documents. In contrast, much of the textual content on the web, and especially social media, is temporally sequenced, and comes in short fragments, including microblog posts on sites such as Twitter and Weibo, status updates on social networking sites such as Facebook and LinkedIn, or comments on content sharing sites such as YouTube. In this paper we propose a novel topic model, Temporal-LDA or TM-LDA, for efficiently mining text streams such as a sequence of posts from the same author, by modeling the topic transitions that naturally arise in these data. TM-LDA learns the transition parameters among topics by minimizing the prediction error on topic distribution in subsequent postings. After training, TM-LDA is thus able to accurately predict the expected topic distribution in future posts. To make these predictions more efficient for a realistic online setting, we develop an efficient updating algorithm to adjust the topic transition parameters, as new documents stream in. Our empirical results, over a corpus of over 30 million microblog posts, show that TM-LDA significantly outperforms state-of-the-art static LDA models for estimating the topic distribution of new documents over time. We also demonstrate that TM-LDA is able to highlight interesting variations of common topic transitions, such as the differences in the work-life rhythm of cities, and factors associated with area-specific problems and complaints.

Latent semantic analysis (LSA) has been intensively studied because of its wide application to Information Retrieval and Natural Language Processing. Yet, traditional models such as LSA only examine one (current) version of the document. However, due to the recent proliferation of collaboratively generated content such as threads in online forums, Collaborative Question Answering archives, Wikipedia, and other versioned content, the document generation process is now directly observable. In this study, we explore how this additional temporal information about the document evolution could be used to enhance the identification of latent document topics. Specifically, we propose a novel hidden-topic modeling algorithm, temporal Latent Semantic Analysis (tLSA), which elegantly extends LSA to modeling document revision history using tensor decomposition. Our experiments show that tLSA outperforms LSA on word relatedness estimation using benchmark data, and explore applications of tLSA for other tasks.

The generative process underlies many information retrieval models, notably statistical language models. Yet these models only examine one (current) version of the document, effectively ignoring the actual document generation process. We posit that a considerable amount of information is encoded in the document authoring process, and this information is complementary to the word occurrence statistics upon which most modern retrieval models are based. We propose a new term weighting model, Revision History Analysis (RHA), which uses the revision history of a document (e.g., the edit history of a page in Wikipedia) to redefine term frequency - a key indicator of document topic/relevance for many retrieval models and text processing tasks. We then apply RHA to document ranking by extending two state-of-the-art text retrieval models, namely, BM25 and the generative statistical language model (LM). To the best of our knowledge, our paper is the first attempt to directly incorporate document authoring history into retrieval models. Empirical results show that RHA provides consistent improvements for state-of-the-art retrieval models, using standard retrieval tasks and benchmarks.