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Ontology-based data integration

Ontology-based data integration. Maurizio Lenzerini Dipartimento di Informatica e Sistemistica “A. Ruberti” Università di Roma “La Sapienza”. DASI ’06: Phd School on Data and Service Integration Bertinoro, December 11–15, 2006. Data integration architecture. Parameters.

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Ontology-based data integration

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  1. Ontology-based data integration Maurizio Lenzerini Dipartimento di Informatica e Sistemistica “A. Ruberti” Università di Roma “La Sapienza” DASI ’06: Phd School on Data and Service Integration Bertinoro, December 11–15, 2006

  2. Data integration architecture

  3. Parameters • Which Description Logic for the ontology • We will mention different possibilites • Which language for user queries • Unions of conjunctive queries • Which type of mapping • We will consider mappings of type GAV • Which sources • Relational sources

  4. OWL-DL OWL concept constructors:

  5. OWL-DL Types of axioms:

  6. The Description Logic DL-lite

  7. DL-lite

  8. DL-lite - example Manages Manages

  9. Dl-lite - semantics

  10. Results on data complexity

  11. A note on mappings • In Ontology-based integration we have to deal with the “impedence mismatch” problem • Sources store data, while instances of concepts and relations in the ontologies are objects • The solution is to define a mapping language that allows specifying how to transform data into objects • Basic idea: use “Skolem functions” in the head of the mapping • Semantics: objects are denoted by “terms” (of exaclty one level of nesting), and different terms are different objects (unique name assumption on terms)

  12. Mappings: example Three sources on students: • s1 uses code for identifying students • s3 uses number for identifying • s2 stores (incomplete) correspondences between code and number Student(sbc(code)) :- s1(code,dob,addr,city) Student(sbc(code)) :- s2(number,code) Student(sbn(number)) :- s3(number,addr,city), not s2(number,code) LivesIn(sbc(code),c(city)) :-s1(code,dob,addr,city), city is not null LivesIn(sbc(code),c(city3)) :- s1(code,dob,addr,city1), city1 is null, s2(number,code), s3(number,addr,city3), city3 is not null LivesIn(sbc(code),c(city3)) :- not s1(code,dob,addr,city1), s2(number,code), s3(number,addr,city3), city3 is not null LivesIn(sbn(number),c(city)) :- s3(number,address,city), city is not null, not s2(number,code)

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