1. Università degli studi Roma Tre 1 Management of heterogeneity in the Semantic Web Paolo Atzeni Pierluigi Del Nostro Semantic Web and Databases Atlanta, Georgia, USA April, 2006

2. Management of heterogeneity in the Semantic Web Università degli studi Roma Tre Paolo Atzeni - Pierluigi Del Nostro 2 Semantic Web Many languages and models exist Interoperability is the challenge, with a generic approach

3. Management of heterogeneity in the Semantic Web Università degli studi Roma Tre Paolo Atzeni - Pierluigi Del Nostro 3 Semantic Web tecnologies Two families of standards OWL ConstraintsTMCL RDFSchema RDFData modelsTopic maps RDF/XML, N3SyntaxesXTM, HyTM, LTM ISOW3C RDF Topic maps

4. Management of heterogeneity in the Semantic Web Università degli studi Roma Tre Paolo Atzeni - Pierluigi Del Nostro 4 Outline 1)RDF and Topic maps : what they share 2)RDF definition 3)Topic maps definition 4)RDF vs Topic maps : differences 5)Model independent approach Meta-constructs Super model Translation process

5. Management of heterogeneity in the Semantic Web Università degli studi Roma Tre Paolo Atzeni - Pierluigi Del Nostro 5 RDF and Topic Maps Both RDF and Topic Maps : consist of standard family attempt to apply knowledge representation techniques to information management define abstract models and interchange syntaxes based on XML have models that are simple and elegant at one level but extremely powerful at another

6. Management of heterogeneity in the Semantic Web Università degli studi Roma Tre Paolo Atzeni - Pierluigi Del Nostro 6 RDF (Resource Description Framework) Based on three concepts Resource: all it is possible to describe. Each resource is identified by an URI (not only web resources) Property: an attribute associated with the resource. Statement: all is it possible to say about resources. It has the form of the triple where: Subject: resource Predicate: property Object: resource/literal

7. Management of heterogeneity in the Semantic Web Università degli studi Roma Tre Paolo Atzeni - Pierluigi Del Nostro 7 RDF (example)

8. Management of heterogeneity in the Semantic Web Università degli studi Roma Tre Paolo Atzeni - Pierluigi Del Nostro 8 Topic Maps A standard for defining knowledge structures and associating them with information resources Topic maps are organized around the concept of Topic, which is used to represent some real-world thing Three constructs are provided for describing the subjects represented by the topics: Names: multiple base names to a single topic and variants of each base name Occurrences: a topic may be linked to one or more information resources that are deemed to be relevant to the topic Associations: have a type, can be n-ary and each topic participate with a specific role

9. Management of heterogeneity in the Semantic Web Università degli studi Roma Tre Paolo Atzeni - Pierluigi Del Nostro 9 Topic Maps (example) predation association role predator prey Cats are furry carnivorous animals… cats.doc Birds are feathery animals… birds.doc occurrence birds cats

10. Management of heterogeneity in the Semantic Web Università degli studi Roma Tre Paolo Atzeni - Pierluigi Del Nostro 10 RDF vs Topic Maps RDFDifferencesTopic maps formal logic and mathematical graph theory roots finding aids: indexes, glossaries, thesauri machinesperspectiveshumans resource-centricpoints of viewsubject-centric "lower-level"levels of semantic"higher-level" addressable by URIsubjects may be addressable or not binary, have directionassertions n-ary, bidirectional, participants with roles

11. Management of heterogeneity in the Semantic Web Università degli studi Roma Tre Paolo Atzeni - Pierluigi Del Nostro 11 Our approach Translation between Semantic Web models handled with a metamodel tecnique developed for translating schemas from a datamodel to another

12. Management of heterogeneity in the Semantic Web Università degli studi Roma Tre Paolo Atzeni - Pierluigi Del Nostro 12 Constructs: a classification Lexical types Sets of printable values The domain Abstract types Entity type, set of objects in the world Class, set of objects in the system Aggregation a construction based on (subsets of) cartesian products Relationship in the E-R model Relation in the relational model Function Attribute in the E-R model Function in a functional data model Grouping Hierarchies A model can be defined in terms of the meta-constructs its constructs refer to E.g., the E-R model: Abstract (called Entity) Function from Abstract to Lexical (Attribute) Aggregation of abstracts (Relationship)

13. Management of heterogeneity in the Semantic Web Università degli studi Roma Tre Paolo Atzeni - Pierluigi Del Nostro 13 The supermodel A model that includes all the meta-constructs (in their most general forms) Each model is subsumed by the supermodel Each schema for any model is also a scheme for the supermodel Translations are realized within the supermodel It needs to be extended to properly represent Semantic Web formalisms The separation between schemas and instances is not strong

14. Management of heterogeneity in the Semantic Web Università degli studi Roma Tre Paolo Atzeni - Pierluigi Del Nostro 14 Super model The translation process SM_S1 SM_S2 copy correspondencecorrespondence S1 schema Topic maps model RDF model SM_RDFSM_TM translation S2 schema

15. Management of heterogeneity in the Semantic Web Università degli studi Roma Tre Paolo Atzeni - Pierluigi Del Nostro 15 The extended supermodel SM_Abstract(schemaOID, abstractOID, name, class/instance, isProperty) SM_Collection(schemaOID, collectionOID, name, type) SM_ComponentOfCollection(schemaOID, componentOID, name, objectOID, collectionOID, position, lexicalValue) SM_Identity(schemaOID, identityOID, name, type, value, objectOID, idObjectOID, idAssertionOID) SM_AttributeOfAbstract(schemaOID, attributeOID, name, subjectOID, predicateOID, objectOID) SM_AggregationOfAbstract(schemaOID, aggregationOID, name) SM_ComponentOfAggregation(schemaOID, componentOID, name, aggregationOID, roleOID, memberOID) SM_Assertion(schemaOID, assertionOID, name) SM_InstanceOf(schemaOID, attributeOID, name, instanceOID, classOID) SM_SubClassOf(schemaOID, attributeOID, name, subclassOID, superclassOID) SM_Scope(schemaOID, attributeOID, name, assertionOID, scopeOID) SM_Type(schemaOID, attributeOID, name, assertionOID, typeOID) SM_AssertionAboutAssertion(schemaOID, assOID, name, assSubjOID, objectOID, lexicalValue) SM_Domain(schemaOID, attributeOID, name, propertyOID, domainOID) SM_Range(schemaOID, attributeOID, name, propertyOID, rangeOID)

16. Management of heterogeneity in the Semantic Web Università degli studi Roma Tre Paolo Atzeni - Pierluigi Del Nostro 16 Super model The translation process SM_S1 SM_S2 copy correspondencecorrespondence S1 schema Topic maps model RDF model SM_RDFSM_TM translation S2 schema

17. Management of heterogeneity in the Semantic Web Università degli studi Roma Tre Paolo Atzeni - Pierluigi Del Nostro 17 Correspondences RDF to SM TM to SM

18. Management of heterogeneity in the Semantic Web Università degli studi Roma Tre Paolo Atzeni - Pierluigi Del Nostro 18 Super model The translation process SM_S1 SM_S2 copy correspondencecorrespondence S1 schema Topic maps model RDF model SM_RDFSM_TM translation S2 schema

19. Management of heterogeneity in the Semantic Web Università degli studi Roma Tre Paolo Atzeni - Pierluigi Del Nostro 19 Translation rules Datalog variant with: OID invention, Skolem functions are used to generate new identifiers when needed Elementary rules are composed in order to obtain complex translation. SM_AttributeOfAbstract ( sOID, assOID(cOID1, cOID2), N(agN, cN1, cN2), ‘null’, mOID1, mOID2) ← SM_AggregationOfAbstract(sOID, agOID, agN), SM_ComponentOfAggregation(sOID, cOID1, cN1, agOID, mOID1, rOID1), SM_ComponentOfAggregation(sOID, cOID2, cN2, agOID, mOID2, rOID2), cOID1<>cOID2

20. Management of heterogeneity in the Semantic Web Università degli studi Roma Tre Paolo Atzeni - Pierluigi Del Nostro 20 Schema representation inside the Super model type John Smith Author Home_JS WebPage type predicate AuthorOf RDF_AllResources RDF_Resources RDF_Statement

21. Management of heterogeneity in the Semantic Web Università degli studi Roma Tre Paolo Atzeni - Pierluigi Del Nostro 21 type Schema representation inside the Super model John Smith Author Home_JS AuthorOf association role Author WebPage instanceOf TM_Topic TM_Association TM_ComponentOfAssociation John Smith Author Home_JS WebPage type predicate AuthorOf

22. Management of heterogeneity in the Semantic Web Università degli studi Roma Tre Paolo Atzeni - Pierluigi Del Nostro 22 Conclusions Model independent approach to the translation Thought for database models Extended to embody Semantic Web formalisms Work in progress Currently developing the details of the translations by using the prototype ModelGen

23. Università degli studi Roma Tre 23 Management of heterogeneity in the Semantic Web Paolo Atzeni Pierluigi Del Nostro Semantic Web and Databases Atlanta, Georgia, USA April, 2006 Thank you Thank you