Università degli studi Roma Tre
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Management of heterogeneity in the Semantic Web
Paolo Atzeni Pierluigi Del Nostro
Semantic Web and DatabasesAtlanta, Georgia, USAApril, 2006
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
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
OWLConstraints TMCL
RDFSchema
RDF Data models Topic maps
RDF/XML, N3 Syntaxes XTM, HyTM, LTM
ISOISOW3CW3C
RDF Topic maps
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 approachMeta-constructsSuper modelTranslation process
Management of heterogeneity in the Semantic Web
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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
Management of heterogeneity in the Semantic Web
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RDF (Resource Description Framework)
Based on three conceptsResource: 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
Management of heterogeneity in the Semantic Web
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Paolo Atzeni - Pierluigi Del Nostro 7
RDF (example)
Management of heterogeneity in the Semantic Web
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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 nameOccurrences: 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
Management of heterogeneity in the Semantic Web
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Topic Maps (example)
predation
associationrole role
predator prey
Cats are furry carnivorous animals…
Cats are furry carnivorous animals…
cats.doc
Birds are feathery animals…
Birds are feathery animals…
birds.doc
occurrence occurrence
birdscats
Management of heterogeneity in the Semantic Web
Università degli studi Roma Tre
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RDF vs Topic Maps
RDF Differences Topic maps
formal logic and mathematical graph theory
rootsfinding aids: indexes, glossaries, thesauri
machines perspectives humans
resource-centric points of view subject-centric
"lower-level" levels of semantic "higher-level"
addressable by URI subjectsmay be addressable or not
binary, have direction assertionsn-ary, bidirectional, participants with roles
Management of heterogeneity in the Semantic Web
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Our approach
Translation between Semantic Web models handled with a metamodel tecnique developed for translating schemas from a datamodel to another
Management of heterogeneity in the Semantic Web
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Constructs: a classification
Lexical typesSets of printable valuesThe domain
Abstract types Entity type, set of objects in the worldClass, set of objects in the system
Aggregationa construction based on (subsets of) cartesian productsRelationship in the E-R modelRelation in the relational model
Function Attribute in the E-R modelFunction 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)
Management of heterogeneity in the Semantic Web
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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
Management of heterogeneity in the Semantic Web
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Super modelSuper model
The translation process
SM_S1 SM_S2
copy copy
correspondencecorrespondence correspondencecorrespondence
S1
schema
Topic maps
model
RDF
model
SM_RDFSM_RDF SM_TMSM_TMtranslation
S2
schema
Management of heterogeneity in the Semantic Web
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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)
Management of heterogeneity in the Semantic Web
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Super modelSuper model
The translation process
SM_S1 SM_S2
copy copy
correspondencecorrespondence correspondencecorrespondence
S1
schema
Topic maps
model
RDF
model
SM_RDFSM_RDF SM_TMSM_TMtranslation
S2
schema
Management of heterogeneity in the Semantic Web
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Correspondences
RDF to SM
TM to SM
Management of heterogeneity in the Semantic Web
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Super modelSuper model
The translation process
SM_S1 SM_S2
copy copy
correspondencecorrespondence correspondencecorrespondence
S1
schema
Topic maps
model
RDF
model
SM_RDFSM_RDF SM_TMSM_TMtranslation
S2
schema
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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
Management of heterogeneity in the Semantic Web
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Schema representation inside the Super modeltype
John SmithJohn Smith AuthorAuthor
Home_JSHome_JS WebPageWebPagetype
predicateAuthorOfAuthorOf
RDF_AllResources
RDF_Resources
RDF_Statement
schemaOID resourceOID Name URI 1 1 John Smith www.peaple.com/#32500 1 2 Home_JS www.home_js.com 1 3 Author www.mine.com/classes#author 1 4 WebPage www.mine.com/classes#webpage 1 5 AuthorOf www.mine.com/properties#authorof
schemaOID resourceOID Name IsClass IsProperty 1 1 John Smith
1 2 Home_JS
1 3 Author
1 4 WebPage
1 5 AuthorOf
schemaOID statementOID Name subjectOID predicateOID objectOID 1 1 JS_AuthorOf_HP 1 5 2
Management of heterogeneity in the Semantic Web
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type
Schema representation inside the Super model
John SmithJohn Smith
AuthorAuthor
Home_JSHome_JSAuthorOfAuthorOf
associationrole role
AuthorAuthor WebPageWebPage
WebPageWebPage
instanceOf instanceOf
schemaOID topoicOID Name IsClass 2 1 John Smith
2 2 Home_JS
2 3 Author
2 4 WebPage
2 5 AuthorOf
2 22 Property
2 23 Subject
2 24 Object
TM_Topic
TM_Association
TM_ComponentOfAssociation
schemaOID assocOID Name 1 1 JS_AuthorOf_HP
schemaOID componentOID Name assocOID roleOID memberOID 2 4 C1_JS_AuthorOf_HP 1 3 1 2 5 C2_JS_AuthorOf_HP 1 4 2
John SmithJohn Smith AuthorAuthor
Home_JSHome_JS WebPageWebPagetype
predicateAuthorOfAuthorOf
Management of heterogeneity in the Semantic Web
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Conclusions
Model independent approach to the translationThought for database modelsExtended to embody Semantic Web formalisms
Work in progressCurrently developing the details of the translations by using the prototype ModelGen
Università degli studi Roma Tre
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Management of heterogeneity in the Semantic Web
Paolo Atzeni Pierluigi Del Nostro
Semantic Web and DatabasesAtlanta, Georgia, USAApril, 2006
Thank Thank youyou
Thank Thank youyou