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Öğe A Financial Cost Metric for Result Caching(Assoc Computing Machinery, 2013) Sazoglu, Fethi Burak; Cambazoglu, B. Barla; Ozcan, Rifat; Altingovde, Ismail Sengor; Ulusoy, OzgurWeb search engines cache results of frequent and/or recent queries. Result caching strategies can be evaluated using different metrics, hit rate being the most well-known. Recent works take the processing overhead of queries into account when evaluating the performance of result caching strategies and propose cost-aware caching strategies. In this paper, we propose a financial cost metric that goes one step beyond and takes also the hourly electricity prices into account when computing the cost. We evaluate the most well-known static, dynamic, and hybrid result caching strategies under this new metric. Moreover, we propose a financial-cost-aware version of the well-known LRU strategy and show that it outperforms the original LRU strategy in terms of the financial cost metric.Öğe A Suggested Picture of Web Search in Turkish(Assoc Computing Machinery, 2016) Sarigil, Erdem; Yilmaz, Oguz; Altingovde, Ismail Sengor; Ozcan, Rifat; Ulusoy, OzgurAlthough query log analysis provides crucial insights about Web users' search interests, conducting such analyses is almost impossible for some languages, as large-scale and public query logs are quite scarce. In this study, we first survey the existing query collections in Turkish and discuss their limitations. Next, we adopt a novel strategy to obtain a set of Turkish queries using the query autocompletion services from the four major search engines and provide the first large-scale analysis of Web queries and their results in Turkish.Öğe HandVR: a hand-gesture-based interface to a video retrieval system(Springer London Ltd, 2015) Genc, Serkan; Bastan, Muhammet; Gudukbay, Ugur; Atalay, Volkan; Ulusoy, OzgurUsing one's hands in human-computer interaction increases both the effectiveness of computer usage and the speed of interaction. One way of accomplishing this goal is to utilize computer vision techniques to develop hand-gesture-based interfaces. A video database system is one application where a hand-gesture-based interface is useful, because it provides a way to specify certain queries more easily. We present a hand-gesture-based interface for a video database system to specify motion and spatiotemporal object queries. We use a regular, low-cost camera to monitor the movements and configurations of the user's hands and translate them to video queries. We conducted a user study to compare our gesture-based interface with a mouse-based interface on various types of video queries. The users evaluated the two interfaces in terms of different usability parameters, including the ease of learning, ease of use, ease of remembering (memory), naturalness, comfortable use, satisfaction, and enjoyment. The user study showed that querying video databases is a promising application area for hand-gesture-based interfaces, especially for queries involving motion and spatiotemporal relations.Öğe How K-12 Students Search For Learning? Analysis of an Educational Search Engine Log(Assoc Computing Machinery, 2014) Usta, Arif; Altingovde, Ismail Sengor; Vidinli, Ibrahim Bahattin; Ozcan, Rifat; Ulusoy, OzgurIn this study, we analyze an educational search engine log for shedding light on K-12 students' search behavior in a learning environment. We specially focus on query, session, user and click characteristics and compare the trends to the findings in the literature for general web search engines. Our analysis helps understanding how students search with the purpose of learning in an educational vertical, and reveals new directions to improve the search performance in the education domain.Öğe Mobile Image Search Using Multi-Query Images(Ieee, 2015) Calisir, Fatih; Bastan, Muhammet; Gudukbay, Ugur; Ulusoy, OzgurRecent advances in mobile device technology have turned the mobile phones into powerfull devices with high resolution cameras and fast processing capabilities. Having more user interaction potential compared to regular PCs, mobile devices with cameras can enable richer content-based object image queries: the user can capture multiple images of the query object from different viewing angles and at different scales, thereby providing much more information about the object to improve the retrieval accuracy. The goal of this paper is to improve the mobile image retrieval performance using multiple query images. To this end, we use the well-known bag-of-visual-words approach to represent the images, and employ early and late fusion strategies to utilize the information in multiple query images. With extensive experiments on an object image dataset with a single object per image, we show that multi-image queries result in higher average precision performance than single image queries.Öğe Mobile multi-view object image search(Springer, 2017) Calisir, Fatih; Bastan, Muhammet; Ulusoy, Ozgur; Gudukbay, UgurHigh user interaction capability of mobile devices can help improve the accuracy of mobile visual search systems. At query time, it is possible to capture multiple views of an object from different viewing angles and at different scales with the mobile device camera to obtain richer information about the object compared to a single view and hence return more accurate results. Motivated by this, we propose a new multi-view visual query model on multi-view object image databases for mobile visual search. Multi-view images of objects acquired by the mobile clients are processed and local features are sent to a server, which combines the query image representations with early/late fusion methods and returns the query results. We performed a comprehensive analysis of early and late fusion approaches using various similarity functions, on an existing single view and a new multi-view object image database. The experimental results show that multi-view search provides significantly better retrieval accuracy compared to traditional single view search.Öğe Propagating Expiration Decisions in a Search Engine Result Cache(Assoc Computing Machinery, 2015) Sazoglu, Fethi Burak; Altingovde, Ismail Sengor; Ozcan, Rifat; Barla Cambazoglu, B.; Ulusoy, OzgurDetecting stale queries in a search engine result cache is an important problem. In this work, we propose a mechanism that propagates the expiration decision for a query to similar queries in the cache to re-adjust their time-to-live values.Öğe Second Chance: A Hybrid Approach for Dynamic Result Caching and Prefetching in Search Engines(Assoc Computing Machinery, 2013) Ozcan, Rifat; Altingovde, Ismail Sengor; Barla Cambazoglu, B.; Ulusoy, OzgurWeb search engines are known to cache the results of previously issued queries. The stored results typically contain the document summaries and some data that is used to construct the final search result page returned to the user. An alternative strategy is to store in the cache only the result document IDs, which take much less space, allowing results of more queries to be cached. These two strategies lead to an interesting trade-off between the hit rate and the average query response latency. In this work, in order to exploit this trade-off, we propose a hybrid result caching strategy where a dynamic result cache is split into two sections: an HTML cache and a docID cache. Moreover, using a realistic cost model, we evaluate the performance of different result prefetching strategies for the proposed hybrid cache and the baseline HTML-only cache. Finally, we propose a machine learning approach to predict singleton queries, which occur only once in the query stream. We show that when the proposed hybrid result caching strategy is coupled with the singleton query predictor, the hit rate is further improved.Öğe Strategies for Setting Time-to-Live Values in Result Caches(Assoc Computing Machinery, 2013) Sazoglu, Fethi Burak; Cambazoglu, B. Barla; Ozcan, Rifat; Altingovde, Ismail Sengor; Ulusoy, OzgurIn web query result caching, staleness of queries are often bounded via a time-to-live (TTL) mechanism, which expires the validity of cached query results at some point in time. In this work, we evaluate the performance of three alternative TTL mechanisms: time-based TTL, frequency-based TTL, and click-based TTL. Moreover, we propose hybrid approaches obtained by pair-wise combination of these mechanisms. Our results indicate that combining time-based TTL with frequency-based TTL yields superior performance (i.e., lower stale query traffic and less redundant computation) than using a particular mechanism in isolation.
