Browser-based Semantic Mapping Tool for Linked Data in Semantic Web Chunying Zhou Chengli Xu, Huajun Chen Kingsley Idehen College of Computer Science, College of Computer Science, OpenLink Software Inc Zhejiang University, China Zhejiang University, China 10 Burlington Mall Road Suite 265 Hangzhou, 310027, China Hangzhou, 310027, China Burlington, MA 01803, U.S.A zcy1982@zju.edu.cn superekcah@gmail.com kidehen@openlinksw.com huajunsir@zju.edu.cn ABSTRACT semantic mapping from relational schema to RDF schema. With the ever growing need of semantically linking data across In this paper, we present a well developed browser-based different domain, organizational and diplomacy boundaries using mapping tool for converting linked data from Web to Semantic RDF and OWL, one of the major obstacles impeding the Web. Before developing the tool, we verified fundamental model advancement of Semantic Web is the data availability. This paper difference between relational schema and the RDF schema and presents a browser-based semantic mapping tool for converting specified a set of mapping issues and mapping cases based on the linked data on the Web to be available for Semantic Web THALIA 2 Testbed. Based on these advance work, we developed applications. It is aiming at helping users define semantic this browser-based mapping engine to help users to define mapping from relational databases to RDF schemas. This tool semantic mapping. It provides a lot of powerful functionalities to provides much easy-to-use functionality to facilitate users in this facilitate domain experts in defining semantic mappings. In definition work, such as drag-and-drop mapping, visualization particular, the tool is able to deal with complex relational schema mapping, data source annotation, database server independent, with complex joins. Besides, it also provides a functionality of standard mapping language and shared ontology management. transforming relational data to RDF data. Categories and Subject Descriptors 2. Browser-based Semantic Mapping Tool H.4.m [Information Systems Applications]: Miscellaneous This semantic mapping tool is developed based on the OAT (OpenLink Ajax Toolkit) framework and Virtuoso Universal General Terms Server 3 . This tool is a web engine defining semantic mapping Management, Design, Reliability, Languages, Theory, Aspects. from heterogeneous databases to shared ontology namely from relational schema to RDF schema. Keywords Ontology, Semantic Mapping, Relational Database, RDF, Linked 2.1 Architecture Data, Semantic Web. This tool aims at helping users to define semantic mapping from relational schema to RDF schema, which needs additional components to support such as data source annotation, shared 1. INTRODUCTION ontology management, and file management. As the figure 2.1 With the fast development of Web, millions of linked document shows, it is composed of three main components: and linked data are stored in online web applications. As a result, the Web becomes a global information center with not only linked z Mapping tool for linked data: This component is the main documents, but also linked data. In particular, most of linked data functional part of this tool, which provides much are stored in relational databases that are always adopted as the functionality to define semantic mappings from relational data storing space by online web applications. Nowadays, one of schema to RDF schema by drag-and-drop. In the end, it also the major obstacles impeding the development of Semantic Web supports saving the defined mappings as Meta Schema is the data availability. It is an opportunity to convert these linked Language, which is defined as script to transform relational data into Semantic Web as the data sources for semantic data to RDF data executed on Virtuoso Universal Server. applications. However, one problem is how to integrate z Virtuoso Universal Server: This component is charge of heterogeneous and distributed relational databases. One of the interactions with databases, including obtaining Meta mature solutions of this problem is integrating heterogeneous data schema information, executing queries, and transform sources using ontology based on semantic mapping, which are relational data to RDF data. mappings from database schema to RDF 1 [1]. Therefore, it calls for powerful mapping mechanism and mapping tools to define Copyright is held by the author/owner(s). 2 LDOW2008, April 22, 2008, Beijing, China.Conference’04, Month 1–2, THALIA:http://esw.w3.org/topic/TaskForces/CommunityProject s/LinkingOpenData/THALIATestbed 1 3 RDF: http://www.w3.org/TR/1999/REC-rdf-syntax-19990222/ OpenLink: http://www.openlinksw.com/virtuoso/ z Physical databases: The physical databases stores millions z Database server independent – The mapping tool is of linked data on the Web. able to support many usual databases, such as Oracle, Mysql and so on. Browser-based Mapping Tool for Linked Data z Drag-and-drop mapping – Users are able to just drag and drop items to complete the process of defining semantic mappings. Data Ontology Other File Resource Resource Resource Registery Viewer Management Management z Mapping Visualization – After user dragging and dropping, the items and semantic mappings are visualized and displayed in the edit domain. And this feature makes the engine easier to extend. Ajax Database Connection RDF componet Http/WebDAV component of OAT of OAT z Data source annotation – Structures of data sources are displayed in the view on the left side, on the other hand, ontology schema are displayed in the view on Virtuoso Universal Server the right side. Physical Databases z Semi-automatic mapping for complex join – Based on table-to-class mappings, it can semi-automatically Figure 2.1 shows the architecture of the mapping tool define mappings for complex joins. 2.2 Functionalities and Features The browser-based mapping tool is well developed to help 1. Display domain experts define semantic mapping from relational schema relational tables to RDF schema. In particular, it provides much easy-to-use 4. Indicate the 3.Drops tables and classes and existence of establishs their functionality and has some special technical features. In this joins bewteen tables mappings. section, we describe these functionalities and features in details. 2.2.1 Functionalities Figure 2.2 depicts the browser-based mapping tool, including resource views, editing domains, and mapping visualization. It consists of three primary functional components as follows: 2. Display ontologies. — Building table-to-class mappings: At first, “table” items are dragged from DbResView and dropped under the edit domain; then ontology classes are dragged from OntoView and dropped under the “table” area. Secondly, users drag properties from OntoView and drop them under ontology class, then drag columns of the “table” from DbResView Figure 2.2 shows display of browser-based mapping tool. and drop them under the property areas. 3. Conclusion and future work — Building complex join mappings: Taking table-to-class This paper presents a browser-based semantic mapping tool for mappings as the inputs, the tool determines whether there linked data in Semantic Web. It has been well designed and are joins between the tables based on semantic relationships accomplished to facilitate users in defining mappings. At present, defined in the shared ontology. this tool is under testing stage accessed in http://ec2-67-202-22- 44.compute-1.amazonaws.com:8890/demo/mapper. — Meta Schema Language: This tool use Meta Schema In our plan, the tool will be enhanced with some heuristic rules Language as semantic mapping description language. After to automate the semantic mapping task as far as possible, just like defining the mapping from relational schema to RDF the approach proposed by Yuan An and colleagues [2]. schema, it provides a functionality to save mappings in Meta Schema Language, which is able to be directly 4. REFERENCES executed on Virtuoso Universal Server to transform [1] Chen,H., Wu,Z., Wang,H., Mao,Y.: Rdf/rdfs - based relational data to RDF data. relational database integration. In International Conference on Data Engineering (ICDE). Pages 94 2.2.2 Technical Functionalities [2] An,Yuan., Borgida,A., Mylopoulos,J. Inferring complex The browser-based mapping tool has many special technical semantic mappings between relational tables and ontologies features, which make it outstanding among the other existing from simple correspondences. In International Semantic Web semantic mapping tools, such as: Conference. Pages 6-20.