università degli studi roma tre 1 management of heterogeneity in the semantic web paolo atzeni...

Università degli studi Roma Tre

1

Management of heterogeneity in the Semantic Web

Paolo Atzeni Pierluigi Del Nostro

Semantic Web and DatabasesAtlanta, Georgia, USAApril, 2006



Paolo Atzeni - Pierluigi Del Nostro 2

Semantic Web

Many languages and models exist

Interoperability is the challenge, with a generic approach




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




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




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




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




RDF (example)




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




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




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




Our approach

Translation between Semantic Web models handled with a metamodel tecnique developed for translating schemas from a datamodel to another




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)




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




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




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)






SM_S1 SM_S2

copy copy


S1

schema

Topic maps

model

RDF

model


S2

schema




Correspondences

RDF to SM

TM to SM






SM_S1 SM_S2

copy copy


S1

schema

Topic maps

model

RDF

model


S2

schema




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




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




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




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


23


Paolo Atzeni Pierluigi Del Nostro

Semantic Web and DatabasesAtlanta, Georgia, USAApril, 2006

Thank Thank youyou

Thank Thank youyou

università degli studi roma tre 1 management of heterogeneity in the semantic web paolo atzeni...

Documents

nostro semantic web

management of heterogeneity

semantic web tecnologies

topic maps definition

rdf vs topic maps

single topic

topic associations

concept of topic