1. ESWC'08 - Tutorial 3 - Transitioning Applications to Ontologies - June, 1st - Tenerife Transitioning Relational Databases to Ontologies Farid Cerbah Dassault Aviation farid.cerbah@dassault-aviation.fr

2. 2 ESWC'08 - Tutorial 3 - Transitioning Applications to Ontologies - June, 1st - Tenerife Outline  Problem statement  Previous work  The RDBToOnto tool and the RTAXON method  Improving the process through database optimisation  A case study in aircraft maintenance  Extending RDBToOnto  Conclusion

3. 3 ESWC'08 - Tutorial 3 - Transitioning Applications to Ontologies - June, 1st - Tenerife Problem statement  Relational databases are valuable heterogeneous sources for ontology learning  Better accuracy can be expected than from text corpora  Ontology learning from relational databases is not a new research issue  Limitations of existing support  Problem often restricted to finding automated ways to import “tables” into ontologies  Derivation of ontologies with flat structure that look like the source databases

4. 4 ESWC'08 - Tutorial 3 - Transitioning Applications to Ontologies - June, 1st - Tenerife Our contribution  RDBToOnto Platform  A comprehensive software support to learn fine- tuned ontologies  A framework that eases the development and the experimentation of transitioning methods  RTAXON Method  To find out taxonomies hidden in the data

5. 5 ESWC'08 - Tutorial 3 - Transitioning Applications to Ontologies - June, 1st - Tenerife A motivating example Typical mappings covered by several methods Specific to RTAXON

6. 6 ESWC'08 - Tutorial 3 - Transitioning Applications to Ontologies - June, 1st - Tenerife Previous work (1)  RDB -> Ontology Transformation  Database Reverse Engineering  Many transformation rules from this domain are reused for ontology learning  [Behm et al. 1997], [Ramanathan & Hodges 1997], …  Approaches mostly based on an analysis of the RDB schema  Data correlations are considered but  with the restriction "Data ≡ Key Values"  Key inclusion may express inheritance  Exploiting null values semantics [Lammari et al. 2007]  Partitioning of a table on the basis of null values may reveal concept hierarchies  Involves data from non-key attributes

7. 7 ESWC'08 - Tutorial 3 - Transitioning Applications to Ontologies - June, 1st - Tenerife Previous work (2)  Mapping languages and tools  D2RQ  RDB to OWL/RDF mapping  Ontology-based access to relational databases  Rewriting SPARQL queries into SQL  Relational.OWL  A minimal ontology of ‘tables’ and ‘column’ and a processor to populate this ontology with data from relational databases  Can be used to exchange data between databases  Triplify  Plugin for web applications  Converts the result of SQL queries into RDF  KAON Reverse  Software support to interactively map an RDB schema to a predefined ontology  DataMaster  Protégé Plugin to import table data into ontologies

8. 8 ESWC'08 - Tutorial 3 - Transitioning Applications to Ontologies - June, 1st - Tenerife RDBToOnto  A user-oriented tool with a full-fledged user interface  Supports an extensive process from the access to the data to ontology generation  Includes the RTAXON converter  Though automated to a large extent, local constraints can be interactively included to progressively refine the ontologies  Types of local constraints  Table and column exclusion  Naming patterns for classes and instances  Categorisation patterns

9. 9 ESWC'08 - Tutorial 3 - Transitioning Applications to Ontologies - June, 1st - Tenerife The RTAXON method  Major improvement over existing methods  Further refine the classes derived from the schema with subclasses found in the content of the relations  Focus on reliable categorisation patterns Demo Access Zones (X 516) A/CCodesDescriptionType F7X2103nose coneDOOR F7X281FLwindshield retainersPANEL F7X300ZZumbrella access panel No.1PANEL F7X243DFservicing compartment floor No.1FLOOR F7X342EZrear under pylon fairingFAIRG Access Zone Door PanelFairing Floor  Two sources involved in the identification of categ. attributes  Attribute names  Revealed by lexical clues  Redundancy in attribute extensions  Entropy-based approach to find good profiles Formal definitionFormal definition of RTAXON Categorising attribute

10. 10 ESWC'08 - Tutorial 3 - Transitioning Applications to Ontologies - June, 1st - Tenerife Optimising the source databases  Another key improvement is the inclusion of a database optimisation step  Many input databases suffer from data duplication problems  Optimisation -> eliminate data duplication through the processing of inclusion dependencies Dassault-AviationF0214 Messier-DowtyF564 ParkerF0086 Name Cage_Code (PKEY) Companies (X 105) Data Duplication eels, Brakes and Braking Landing Gear Emergency Control System Landing Gears Hydraulic Power WP Title ABSB45335 Dassault-AviationF021434A Messier-DowtyF56434 ParkerF008633 Company NameCompany CodeWP Number WorkPackages (X 82) Companies (X 106) eels, Brakes and Braking Landing Gear Emergency Control System Landing Gears Hydraulic Power WP Title B45335 F021434A F56434 F008633 Company CodeWP Number WorkPackages (X 82) Foreign Key Relationship Inclusion dependency

11. 11 ESWC'08 - Tutorial 3 - Transitioning Applications to Ontologies - June, 1st - Tenerife Effect of inclusion dependency processing  Inclusion dependencies  more inter-class relations (i.e. object properties). Without ID identification With ID identification

12. 12 ESWC'08 - Tutorial 3 - Transitioning Applications to Ontologies - June, 1st - Tenerife Identification of inclusion dependencies  RDBToOnto includes an editor to interactively define inclusion dependencies  Automated identification of inclusion dependencies  A data mining approach Based on LATINO  See presentation in this tutorial on ontology learning by Miha Grčar (JSI)  Dependencies discovered by LATINO are exported in RDBToOnto and can be validated in the ID editor

13. 13 ESWC'08 - Tutorial 3 - Transitioning Applications to Ontologies - June, 1st - Tenerife Mining inclusion dependencies with LATINO

14. 14 ESWC'08 - Tutorial 3 - Transitioning Applications to Ontologies - June, 1st - Tenerife A case study in aircraft maintenance KCIT(GATE-based annotator) RDBToOnto + LATINO Radiant OWLIM

15. 15 ESWC'08 - Tutorial 3 - Transitioning Applications to Ontologies - June, 1st - Tenerife The ontology acquisition process  The legacy data  LSA database: an heterogeneous relational database that gathers all information related to maintenance activity  Required logistic resources  Aircraft parts (Product tree)  Scheduling data  Standards: Documents including widely shared conceptual models  The ontology acquisition process  A multi-step transitioning process that favours modular design

16. 16 ESWC'08 - Tutorial 3 - Transitioning Applications to Ontologies - June, 1st - Tenerife Model Boostrapping + Ontology Normalisation <>… …. <> … Reusable Ontologies Ontology Learning Tools MSG-3SNS/ATAFOAF Model Bootstrapping Ontology Normalisation ATA  imports Legacy Data OWLIM/HKS Repository

17. 17 ESWC'08 - Tutorial 3 - Transitioning Applications to Ontologies - June, 1st - Tenerife The defined RDBToOnto conversion project  75 constraints  Mostly naming patterns and inclusion dependencies  Resulting ontology  Ontology model  115 classes, 334 datatypes, 54 object properties  Population  49617 class instances, 51449 object property instances  No constraints for categorisation  The ten discovered hierarchies by RTAXON are relevant  Good behaviour when faced with categorisation conflicts

18. 18 ESWC'08 - Tutorial 3 - Transitioning Applications to Ontologies - June, 1st - Tenerife The generated class hierarchy

19. 19 ESWC'08 - Tutorial 3 - Transitioning Applications to Ontologies - June, 1st - Tenerife Identified object properties

20. 20 ESWC'08 - Tutorial 3 - Transitioning Applications to Ontologies - June, 1st - Tenerife RDBToOnto extension capabilities  RDBToOnto is a user-oriented tool but it is also a framework  Written in Java  OWL as target language (exploiting Jena 2.5 API)  Two types of components can be added  Database readers to cover more database formats  Converters to implement new learning methods  New converters can have their specific global options, local constraints and GUI

21. 21 ESWC'08 - Tutorial 3 - Transitioning Applications to Ontologies - June, 1st - Tenerife Structure of RDBToONTO DBReader Database getDatabase() Table ReadData(String name) … MSAccessReader DB2Reader Database RDBToOntoConverter OntModel Convert(Database db) OntClass CreateClass(TableDef) … RTAXONBasicConverter can be extended by the users

22. 22 ESWC'08 - Tutorial 3 - Transitioning Applications to Ontologies - June, 1st - Tenerife The neutral database model DatabaseDBSchema TableDef Key PrimaryKey ForeignKey Attribute Table Column String friendlyNamesValues * ** * * * * Input to any converter

23. 23 ESWC'08 - Tutorial 3 - Transitioning Applications to Ontologies - June, 1st - Tenerife Conclusion  We presented a significant support for transitioning relational databases to ontologies  RDBToOnto and RTAXON method have been evaluated on significant databases  RTAXON is just a first step as many extensions can be studied  Learning two-level hierarchies  Automatically generating local constraints (e.g. naming patterns)  More resources are available on TAO project web site, including  User Guide and demos  Development Guide  A fully implemented sample showing how to extend the tool