PAUSANIAS: Final activity report

Search engines, such as Google and Yahoo!, provide efficient retrieval and ranking of web pages based on queries consisting of a set of given keywords. Recent studies show that 20% of all Web queries also have location constraints, i.e., also refer to the location of a geotagged web page. An increasing number of applications support location-based keyword search, including Google Maps, Bing Maps, Yahoo! Local, and Yelp. Such applications depict points of interest on the map and combine their location with the keywords provided by the associated document(s). The posed queries consist of two conditions: a set of keywords and a spatial location. The goal is to find points of interest with these keywords close to the location. We refer to such a query as spatial-keyword query. Moreover, mobile devices nowadays are enhanced with built-in GPS receivers, which permits applications (such as search engines or yellow page services) to acquire the location of the user implicitly, and provide location-based services. For instance, Google Mobile App provides a simple search service for smartphones where the location of the user is automatically captured and employed to retrieve results relevant to her current location. As an example, a search for pizza results in a list of pizza restaurants nearby the user. In this research project, we studied how preference queries can be extended for supporting also keywords. To this end we first studied preference queries in order to establish techniques that can be extended for supporting keywords (Chapter 1). Moreover, we proposed Top-k Spatio-Textual Preference Queries and proposed a novel indexing scheme and two algorithms for supporting efficient query processing (Chapter 2). We also studied the problem of maximizing the influence of spatio-textual objects based on reverse top-k queries and keyword selection (Chapter 3). Finally, we analyze the properties of geotagged photos of Flickr, and propose novel location-aware tag recommendation methods (Chapter 4). In summary, this research project lead to the following publications: • George Tsatsanifos, Akrivi Vlachou: On Processing Top-k Spatio-Textual Preference Queries, in Proceedings of 18th International Conference on Extending Database Technology (EDBT), Brussels, Belgium, March 23-27, 2015. • Orestis Gkorgkas, Akrivi Vlachou, Christos Doulkeridis and Kjetil Nørvåg: Finding the Most Diverse Products using Preference Queries, in Proceedings of 18th International Conference on Extending Database Technology (EDBT), Brussels, Belgium, March 23-27, 2015. • Ioanna Miliou, Akrivi Vlachou: Location-Aware Tag Recommendations for Flickr, DEXA (1) 2014: 97-104. • Orestis Gkorgkas, Akrivi Vlachou, Christos Doulkeridis and Kjetil Nørvåg: Efficient Processing of Exploratory Top-k Joins, in Proceedings of 26th International Conference on Scientific and Statistical Database Management (SSDBM), Aalborg, Denmark, June 30 July 2, 2014. • Akrivi Vlachou, Christos Doulkeridis, Kjetil Nørvåg and Yannis Kotidis: Branch-and-Bound Algorithm for Reverse Top-k Queries, in Proceedings of ACM International Conference on Management of Data (SIGMOD), New York, USA, June 22-27, 2013. • Orestis Gkorgkas, Akrivi Vlachou, Christos Doulkeridis and Kjetil Nørvåg: Discovering Influential Data Objects over Time, in Proceedings of 13th International Symposium on Spatial and Temporal Databases (SSTD), Munich, Germany, August 21-23, 2013. • Orestis Gkorgkas, Akrivi Vlachou, Christos Doulkeridis, Kjetil Nørvåg: Maximizing Influence of Spatio-Textual Objects through Keyword Selection submitted for publication. • Orestis Gkorgkas, Akrivi Vlachou, Christos Doulkeridis, Kjetil Nørvåg: Exploratory product search using top-k join queries. submitted for journal publication. The research project is implemented within the framework of the Action Supporting Postdoctoral Researchers of the Operational Program ”Education and Lifelong Learning” (Actions Beneficiary: General Secretariat for Research and Technology), and is co-financed by the European Social Fund (ESF) and the Greek State.