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
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Paolo Atzeni - Pierluigi Del Nostro
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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
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Paolo Atzeni - Pierluigi Del Nostro
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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
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Paolo Atzeni - Pierluigi Del Nostro
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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
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Paolo Atzeni - Pierluigi Del Nostro
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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
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Paolo Atzeni - Pierluigi Del Nostro
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Management of heterogeneity in the Semantic Web
RDF (example)
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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
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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…
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birds.doc
Birds are
feathery
animals…
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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
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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
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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
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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
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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
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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
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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)
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Paolo Atzeni - Pierluigi Del Nostro
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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
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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
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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
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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.
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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
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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
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subjectOID
predicateOID objectOID
1
5
2
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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
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assocOID
1
1
roleOID memberOID
3
1
4
2
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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
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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