™ Suggestions for Semantic Web Interfaces to Relational Databases Mike Dean W3C Workshop on RDF Access to Relational Databases Cambridge, MA 26 October 2007

™ 2 Outline  Our Experience  Desirable Semantic Web Characteristics  Support for Common Patterns  Other Issues  Potential Areas for Standardization

™ 3 Asio Scout Architecture SOAP WS RDBMS Query Decomposition Query: SPARQL Data Access 3 Generation of Sub Queries 6 Query Result Set 5 Semantic Bridge Database Semantic Bridge Web Service Backwards Rule Chaining Snoggle KB Semantic Query Decomposition (SQD) Semantic Bridge SPARQL Endpoint Automapper

™ 4 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

™ 5 Evolution of Approaches  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 DBMS Custom Data source ontology Custom servlet Domain ontology SWRL Translation rules translationapplication

™ 6 Evolution of Approaches  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? DBMS Generic Data source ontology Generic servlet Data source ontology SWRL Translation rules translation “Nice” SW data AutoMapper Domain ontology SWRL Translation rules translationapplication Optional mapping directives

™ 7 Evolution of Approaches  Domain ontology is often augmented with domain- specific business rules  A domain ontology may become someone else’s data source  N-level approach DBMS Generic Data source ontology Generic servlet Data source ontology SWRL Translation rules translation “Nice” SW data AutoMapper Domain ontology SWRL Translation rules translationapplication Optional mapping directives “Busness Rules” inferenceapplication

™ 8 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

™ 9 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

™ 10 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)

™ 11 More Information  –SemTech 2007 presentation/demo