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This presentation discusses the desirable characteristics of a semantic web interface for relational databases, including support for common patterns, query decomposition, semantic bridge, data access, and more.
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Suggestions forSemantic Web Interfacesto Relational Databases Mike Dean mdean@bbn.com W3C Workshop on RDF Access to Relational Databases Cambridge, MA 26 October 2007
Outline • Our Experience • Desirable Semantic Web Characteristics • Support for Common Patterns • Other Issues • Potential Areas for Standardization
SOAP WS RDBMS Asio Scout Architecture 1 Query: SPARQL Snoggle 6 Query Result Set Query Decomposition 2 Semantic Query Decomposition (SQD) Backwards Rule Chaining 5 Generation ofSub Queries 3 Automapper Semantic Bridge Database Semantic Bridge Web Service Semantic Bridge SPARQL Endpoint 4 Data Access KB
Semantic Web Characteristics • Publishing each data model as an OWL ontology • Use of resolvable URIs • Favoring the use of object properties over datatype properties • Use of datatypes • Use of accepted conventions such as camelCaseNames and singular class names • Reuse of or mappings to existing vocabularies such as FOAF and Dublin Core
Evolution of Approaches Custom Data source ontology SWRL Translation rules Domain ontology DBMS Custom servlet translation application • Expose each data source with an OWL representation of its native data model • Use SWRL to represent structural transformations, unit conversions, etc. • Support cross-product of producers and consumers • Gold standard in terms of output quality • Labor-intensive
Evolution of Approaches Optional mapping directives AutoMapper Generic Data source ontology SWRL Translation rules Data source ontology SWRL Translation rules Domain ontology DBMS Generic servlet translation “Nice” SW data translation application • Get the data into Semantic Web format quickly and then apply Semantic Web tools • Much less labor to achieve similar results • How “nice” can we make the first stage output?
Evolution of Approaches Optional mapping directives AutoMapper Generic Data source ontology SWRL Translation rules Data source ontology SWRL Translation rules Domain ontology “Busness Rules” DBMS Generic servlet translation “Nice” SW data translation application inference application • Domain ontology is often augmented with domain-specific business rules • A domain ontology may become someone else’s data source • N-level approach
Support for Common Patterns • Most databases are now designed from an ER or OO model – this higher-level model should be exposed • Parent and child tables for inheritance • Implicit class hierarchies (“type” column) • N-ary relations
Other Issues • Use of resolvable URIs • Support HTTP GET as well as SPARQL • Ensure that returned URIs can be used in subsequent SPARQL queries • “External foreign keys” – links to open data • Security • Non-public data sources require authentication • Performance • Update
Potential Areas for Standardization • Table and column to class and property mappings • SQL datatype to XML Schema datatype mappings • SPARQL to SQL translation • Web service interfaces (including authentication)
More Information • http://asio.bbn.com • SemTech 2007 presentation/demo