Management of heterogeneity in the Semantic Web
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Management of heterogeneity in the Semantic Web
Semantic Web and Databases Atlanta, Georgia, USA April, 2006 Management of heterogeneity in the Semantic Web Paolo Atzeni Università degli studi Roma Tre Pierluigi Del Nostro 1 Management of heterogeneity in the Semantic Web Semantic Web Many languages and models exist Interoperability is the challenge, with a generic approach Università degli studi Roma Tre Paolo Atzeni - Pierluigi Del Nostro 2 Management of heterogeneity in the Semantic Web Semantic Web tecnologies Two families of standards W3C OWL ISO Constraints TMCL RDF Data models Topic maps RDF/XML, N3 Syntaxes XTM, HyTM, LTM RDFSchema Università degli studi Roma Tre Paolo Atzeni - Pierluigi Del Nostro 3 Management of heterogeneity in the Semantic Web 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 Università degli studi Roma Tre Paolo Atzeni - Pierluigi Del Nostro 4 Management of heterogeneity in the Semantic Web 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 Università degli studi Roma Tre Paolo Atzeni - Pierluigi Del Nostro 5 Management of heterogeneity in the Semantic Web 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 <subject, predicate, object> where: Subject: resource Predicate: property Object: resource/literal Università degli studi Roma Tre Paolo Atzeni - Pierluigi Del Nostro 6 Management of heterogeneity in the Semantic Web RDF (example) Università degli studi Roma Tre Paolo Atzeni - Pierluigi Del Nostro 7 Management of heterogeneity in the Semantic Web 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 Università degli studi Roma Tre Paolo Atzeni - Pierluigi Del Nostro 8 Management of heterogeneity in the Semantic Web Topic Maps (example) cats predator role predation association prey birds role occurrence occurrence cats.doc Cats are furry carnivorous animals… Università degli studi Roma Tre birds.doc Birds are feathery animals… Paolo Atzeni - Pierluigi Del Nostro 9 Management of heterogeneity in the Semantic Web RDF vs Topic Maps RDF formal logic and mathematical graph theory machines resource-centric "lower-level" addressable by URI binary, have direction Università degli studi Roma Tre Differences roots perspectives Topic maps finding aids: indexes, glossaries, thesauri humans points of view subject-centric levels of semantic "higher-level" subjects may be addressable or not assertions n-ary, bidirectional, participants with roles Paolo Atzeni - Pierluigi Del Nostro 10 Management of heterogeneity in the Semantic Web Our approach Translation between Semantic Web models handled with a metamodel tecnique developed for translating schemas from a datamodel to another Università degli studi Roma Tre Paolo Atzeni - Pierluigi Del Nostro 11 Management of heterogeneity in the Semantic Web 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 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) Function Attribute in the E-R model Function in a functional data model Grouping Hierarchies Università degli studi Roma Tre Paolo Atzeni - Pierluigi Del Nostro 12 Management of heterogeneity in the Semantic Web 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 Università degli studi Roma Tre Paolo Atzeni - Pierluigi Del Nostro 13 Management of heterogeneity in the Semantic Web The translation process Super model SM_RDF correspondence SM_TM correspondence translation SM_S1 SM_S2 model RDF Università degli studi Roma Tre model copy copy schema schema S1 S2 Paolo Atzeni - Pierluigi Del Nostro Topic maps 14 Management of heterogeneity in the Semantic Web 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) Università degli studi Roma Tre Paolo Atzeni - Pierluigi Del Nostro 15 Management of heterogeneity in the Semantic Web The translation process Super model SM_RDF correspondence SM_TM correspondence translation SM_S1 SM_S2 model RDF Università degli studi Roma Tre model copy copy schema schema S1 S2 Paolo Atzeni - Pierluigi Del Nostro Topic maps 16 Management of heterogeneity in the Semantic Web Correspondences RDF to SM TM to SM Università degli studi Roma Tre Paolo Atzeni - Pierluigi Del Nostro 17 Management of heterogeneity in the Semantic Web The translation process Super model SM_RDF correspondence SM_TM correspondence translation SM_S1 SM_S2 model RDF Università degli studi Roma Tre model copy copy schema schema S1 S2 Paolo Atzeni - Pierluigi Del Nostro Topic maps 18 Management of heterogeneity in the Semantic Web 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. Università degli studi Roma Tre 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 Paolo Atzeni - Pierluigi Del Nostro 19 Management of heterogeneity in the Semantic Web Schema representation inside the Super model John Smith RDF_AllResources schemaOID resourceOID 1 1 1 2 1 3 1 4 1 5 Name URI John Smith www.peaple.com/#32500 Home_JS www.home_js.com Author www.mine.com/classes#author WebPage www.mine.com/classes#webpage AuthorOf www.mine.com/properties#authorof type predicate Home_JS Author AuthorOf type WebPage RDF_Resources schemaOID resourceOID 1 1 Name John Smith 1 2 Home_JS 1 3 Author 1 4 WebPage 1 5 AuthorOf IsClass IsProperty RDF_Statement schemaOID statementOID Name 1 1 JS_AuthorOf_HP Università degli studi Roma Tre subjectOID predicateOID objectOID 1 5 2 Paolo Atzeni - Pierluigi Del Nostro 20 Management of heterogeneity in the Semantic Web Schema representation inside the Super model John Smith type predicate TM_Topic schemaOID 2 topoicOID 1 Name John Smith 2 2 Home_JS 2 3 Author 2 4 WebPage 2 5 AuthorOf 2 22 Property 2 23 Subject 2 24 Object IsClass Home_JS Author John Smith role assocOID association AuthorOf type Home_JS role instanceOf Author Name 1 JS_AuthorOf_HP WebPage WebPage instanceOf TM_Association schemaOID 1 AuthorOf Author WebPage TM_ComponentOfAssociation schemaOID componentOID Name 2 4 C1_JS_AuthorOf_HP 2 5 C2_JS_AuthorOf_HP Università degli studi Roma Tre assocOID 1 1 roleOID memberOID 3 1 4 2 Paolo Atzeni - Pierluigi Del Nostro 21 Management of heterogeneity in the Semantic Web 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 Università degli studi Roma Tre Paolo Atzeni - Pierluigi Del Nostro 22 Semantic Web and Databases Atlanta, Georgia, USA April, 2006 Thank you Management of heterogeneity in the Semantic Web Paolo Atzeni Università degli studi Roma Tre Pierluigi Del Nostro 23