DBpedia Mobile: A Location-Enabled Linked Data Browser Christian Becker Christian Bizer Freie Universität Berlin Freie Universität Berlin Germany Germany chris@beckr.org chris@bizer.de ABSTRACT In this demonstration, we present DBpedia Mobile, a location-centric DBpedia client application for mobile de- vices consisting of a map view and a Fresnel-based Linked Data browser. The DBpedia project extracts structured information from Wikipedia and publishes this informa- tion as Linked Data on the Web. The DBpedia dataset contains information about 2.18 million things, including almost 300,000 geographic locations. DBpedia is interlinked with various other location-related datasets. Based on the current GPS position of a mobile device, DBpedia Mobile renders a map indicating nearby locations from the DBpedia dataset. Starting from this map, users can explore background information about locations and can navigate Figure 1: DBpedia Mobile’s map view of resources into interlinked datasets. DBpedia Mobile demonstrates in the user’s proximity. that the DBpedia dataset can serve as a useful starting point to explore the Geospatial Semantic Web using a mobile device. these locations is interlinked with various other location- related datasets, such as the GeoNames, US Census, CIA Factbook, and EuroStat datasets. Altogether there are Categories and Subject Descriptors around 185,000 external RDF links into other RDF datasets H.3.3 [Information Search and Retrieval]: Information on the Web, making DBpedia an important interlinking- filtering; H.5.4 [Hypertext/Hypermedia]: Navigation hub. The DBpedia resources are classified within three different classification hierarchies. These classifications Keywords provide for the filtering of locations according to their type, which is especially important on mobile devices with limited Semantic Web, Linked Data, Geospatial Web, DBpedia, screen space in order to prevent maps from overpopulating. Location Based Applications 1. INTRODUCTION 2. THE APPLICATION DBpedia Mobile allows users to access information about Mobile phones feature increasingly powerful hardware, DBpedia resources located in their physical vicinity, from software and data connectivity, and more and more phones where they can explore links to other resources on the are shipped with built-in GPS receivers, whose positioning Semantic Web. DBpedia Mobile is accessed using a mobile capabilities are exposed to third party applications. In phone’s web browser; a supplemental launcher application parallel, the Semantic Web is populated with an increasing may be used to initialize DBpedia Mobile with the user’s amount of location-related data. current location as retrieved from a built-in or externally A Semantic Web data source which provides information connected GPS receiver. that could be useful for a tourist exploring a city is DBpedia Mobile’s initial view is an area map that in- DBpedia [1]. The DBpedia dataset1 has been extracted from dicates the user’s position and nearby DBpedia resources Wikipedia. For currently more than 2.18 million “things”, it with appropriate labels and icons. The icons are mapped features labels and short abstracts in 14 different languages, to selected YAGO categories [3]. Figure 1 shows DBpedia 489,000 links to images and 2,715,000 links to external Mobile’s map view running under Opera Mobile 8 on a GPS- web pages. The DBpedia dataset contains information equipped Windows Mobile 6 handset. The map view can be about almost 300,000 locations. DBpedia data about panned by dragging it on the touch screen, or zoomed using 1 the provided controls. In a settings pane, the display may http://dbpedia.org/ be limited to specific resource types such as Museums or Copyright is held by the author/owner(s). Train Stations. Also, the preferred language for labels and LDOW2008, April 22, 2008, Beijing, China. abstracts may be selected from the 14 languages supported Figure 2: A Fresnel-generated summary view of Figure 3: Interlinked data from GeoNames dis- a resource that includes a review obtained from played in the full details view. Revyu. and filter settings to the server, where they are rewritten by DBpedia. Clicking on a resource brings up a Fresnel [2]- as a SPARQL query and issued to a Virtuoso server based Linked Data browser displaying a summary view of that hosts DBpedia’s geocoordinates, article label and the selected item. This view includes a short text describing YAGO classification datasets. The Linked Data browser is the resource and optionally an image, a link to the resource’s implemented as a Java Servlet that generates XHTML views foaf:homepage and reviews from the Revyu2 rating site for given resource URIs and display purposes (summary, if existent. Figure 2 shows an exemplary summary view photo or full details view ). It uses the SIMILE fresnel containing a review obtained from Revyu. engine and the Saxon XSLT processor. The underlying Links at the bottom of the abstract allow the user to data is obtained by dereferencing the resource’s URI and switch to a photo view with depictions of the resource and by following known predicates (owl:sameAs, rdfs:seeAlso, to a full details view of all properties available for the p:hasPhotoCollection) found in that data. Review data resource. These views incorporate information from other is retrieved by issuing a SPARQL CONSTRUCT query against Linked Data sources. For example, geographic resources Revyu’s public SPARQL endpoint. are enriched with information from GeoNames3 and photos are provided by the flickrTM wrappr4 . Figure 3 shows 4. CONCLUSIONS AND FUTURE WORK a DBpedia resource’s full details view that incorporates We have introduced a mobile, location-centric DBpedia linked data from GeoNames. If the displayed data contains client that features a Linked Data browser and generates RDF links into other datasets, the user may click them suitable data views using Fresnel. We have shown that the to obtain a full details view of the referenced resource. DBpedia dataset is well-suited for use as a starting point to In this manner, the user can navigate from the DBpedia explore the Geospatial Semantic Web. dataset into other interlinked datasets. For instance, he As future work, we would like to include resources from could traverse GeoNames’ parentFeature link hierarchy to other Linked Data sources such as GeoNames into the find out more about the city, state and country in which a map display and extend DBpedia Mobile to support the resource is located. publication of Linked Data. For instance, it could be interesting to enable users to tag photos, which they have taken with the phone’s camera, with DBpedia URIs before 3. TECHNICAL BACKGROUND publishing them on the Web. DBpedia Mobile is realized as a client-server applica- More information about DBpedia Mobile is available from tion with searches, data retrieval and storage as well as http://wiki.dbpedia.org/DBpediaMobile. formatting activities performed on the server side. This architecture provides the application with high bandwidth, 5. REFERENCES processing and storage resources, allowing search requests as [1] S. Auer, C. Bizer, J. Lehmann, G. Kobilarov, well as the Fresnel-based view generation to touch on large R. Cyganiak, and Z. Ives. DBpedia: A nucleus for a amounts of data. web of open data. In Proceedings of the 6th The client application is written in JavaScript and can be International Semantic Web Conference and 2nd Asian accessed with web browsers that feature adequate Document Semantic Web Conference (ISWC/ASWC2007), Object Model (DOM) Level 1 and 2 support to host the volume 4825 of LNCS, pages 715–728, Springer, 2007. underlying Google Maps API, such as Opera Mobile 8. [2] E. Pietriga, C. Bizer, D. Karger, and R. Lee. Fresnel: A It is designed for displays with at least QVGA (320 × browser-independent presentation vocabulary for RDF. 240 pixels) resolution. The supplemental GPS launcher In International Semantic Web Conference application is currently available for Windows Mobile 6. (ISWC2006), volume 4273 of of LNCS, pages 158–171, The map view is built from RDF triples obtained by Springer, 2006. sending the currently visible area as well as language [3] F. M. Suchanek, G. Kasneci, and G. Weikum. Yago: A 2 http://revyu.com core of semantic knowledge. 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