DartGrid Browser-based mapping tool of SQL to RDF Point Template Zhejiang University & OpenLink Software

DartGrid Contents Identifies and records the SQL2RDF mapping issues 2 Browser-based mapping tool of SQL to RDF is developed. 4 Why need semantic mapping? 31 Identify a set of mapping cases 33

DartGrid Why need semantic mapping tool? 1. Semantic mapping from Relational databases to RDF is the key problem in RDF-based databases integration. 2 Defining semantic mapping manually is a burdensome and error- prone work. 3 So far, there is none full-automatic mapping tool of SQL to RDF, most of which is defined manually..

DartGrid 2. Mapping cases W3C Banff life scienece demo W3C Banff life scienece demo also has public available SQL versions. Mapping cases THALIA Testbed THALIA Testbed provides a collection of 40 relational database tables representing course information. More:

DartGrid 2.1 Representation and notation 1 Graphical representation: each case is graphically represented for documentation purpose. 3 Syntax level: for implementation purpose, the mappings are finally stored as virtuoso meta- schema language MDL 2 Abstract level: a mapping is abstractly described as a rule that has rule head and rule body.

DartGrid 2.1 Representation and notation(2) 1 Variables : a,b are original column names of the relational table. 3 Uri function : it may be implemented as either generating a blank node ID (internal id) or global URI. 2 uri : It is a function used to generate universal resource identifiers. R(?a,?b,?c,…)-: (uri, rdf:type, thalia:Course), (uri, foaf:name,?b), (uri, thalia:hasInstructor, uri ), (uri, rdf:type, thalia:Instructor)

DartGrid kinds of mapping cases 1 The simplest situation of mapping cases is a single table exactly maps to one single class in the ontology. 2 More complex situation is mapping from one table to four ontological classes 3 Most complex situation is self-join that is three or above tables are connected by foreign key, or one table has foreign key relationship with itself.

DartGrid 2.3 THALIA Testbed 1 The tested relational databases are taken from the THALIA Testbed benchmark.THALIA Testbed 2 It provides a collection of 40 relational database tables representing university course catalogs. 3 The data in the testbed provide a rich source of syntactic and semantic heterogeneities.

DartGrid Description as a rule  Case 1 Arizona State University  The asu table stores CS course information of the Arizona State University.  This mapping case is that a single table exactly maps to one single ontology class.

DartGrid mapping mechanism Fig.1 mapping case 1 of THALIA

DartGrid Brown University case 1 The normal mapping systems often separately consider the schema-level mapping and instance-level mapping. 2 Thialia:hasInstructor should be considered as a property (schema) in RDF, but is stored in a relational tuple(instance). 3 This use case illustrates the mapping from one table to four ontological classes.

DartGrid Description as a rule  The brown table stores CS course information of the Brown University.  This use case illustrates the mapping from one table to four ontological classes: Course, Instructor, Event, Point.

DartGrid mapping mechanism Fig.2 mapping mechanism of Brown case

DartGrid 3. Browser-based mapping tool 1 This mapping tool is developed based on OAT (OpenLink Ajax Toolkit) 3 This mapping tool provides a lot of easy-to-use functionalities and has some special technical features. 2 This mapping tool is developed to help domain experts to define the semantic mapping

DartGrid 3.1 Functional components Display databases and ontology schema structure Define instance-level mappings such as table-to-class or column-to-property Define schema-level mappings (for complex joins between tables) Mapping Tool

DartGrid Instance-level mapping  Instance-level mapping is always simple and easy to understand.  Generally speaking, instance-level mapping has two types:  From tables to ontology classes  From one column to one ontology property  3 situations of mapping tables to classes  From one table to one ontology class  From one table to many ontology classes  From many tables to one ontology class

DartGrid Schema-level mapping  It is more complicated than instance-level mapping, which is based on foreign key relation and relativity defined in ontology schema.

DartGrid 3.2 Technical Features Drag-and-drop mapping Web browser-based tool Visualization mapping Data source annotation semi-auto mapping for complex joins Browser-based Mapping tool Browser-based

DartGrid 3.3 mapping tool pictures Fig.2 DbView/OntoViewFig.3 drag-and-drop mapping

DartGrid 4. Future work Automate Automate mapping process as far as possible by adding some heuristic rules to automate the semantic mapping task. MDL Adopt Virtuoso's SPARQL based Meta schema Language as the syntax mapping rule.

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