MIRROR is a tool that automatically generates R2RML mappings from relational databases. It extracts tables and relationships from the database schema and generates two sets of mappings: 1) mappings that produce direct mapping triples, and 2) mappings that encode the relationships between tables as additional triples. The tool was tested on W3C direct mapping test cases and an extension of the D011 test case to include one-to-many, many-to-many relationships and subclass relationships.

1. MIRROR: Automatic R2RML Mapping
Generation from Relational
Databases
Luciano
Frontino de
Medeiros
Freddy Priyatna
Oscar Corcho
The 15th International Conference on Web Engineering
June 25th, 2015
Rotterdam, the Netherlands

2. Outline
1. Background & Motivation
2. Patterns Extraction
3. Mappings Generation
4. Experimentation
5. Conclusion
2

3. RDB2RDF
3
● Two worlds
o Relational Database (RDB) for storing information
 rows, tables
o Resource Description Framework (RDF) for sharing
information
 triples, graphs
● RDB2RDF and W3C

4. Direct Mapping
● Table URIs
o <ex.com/Student>
● Row nodes
o <Student/ID=10>
● Row type triples
o <Student/ID=10> <rdf:type> Student
● Literal triples
o <Sport/ID=110> <Sport#Description> “Tennis”.
● Reference triples
o <Student_Sport/ID_Student=10;ID_Sport=110> <Student_Sport#ref-ID_Student>
<Student/ID=10> .
4
http://www.w3.org/TR/rdb-direct-mapping/

5. Direct Mapping Example
Student
ID
(PK)
FirstName LastName
10 Venus Williams
11 Fernando Alonso
12 David Villa
Sport
ID
(PK)
Description
110 Tennis
111 Football
112 Formula1
Student_Sport
ID_Student
(PFK)
ID_Sport
(PFK)
10 110
11 111
11 112
12 111
5
<Student/ID=11>
<Student>
11
Fernando Alonso
rdf:type
<Student/ID>
<Student/LastName>
<Student/FirstName>

6. R2RML
● Customized mappings
● Triples Map
o Logical Table
o Subject Map
o Predicate Object Map
 Predicate Map
 Object Map
 Reference Object Map
● Term Map
o constant
o column
o template
6
http://www.w3.org/TR/r2rml/

7. R2RML Example
Student
ID
(PK)
FirstName LastName
10 Venus Williams
11 Fernando Alonso
12 David Villa
7
<Estudiante/11>
<Estudiante>
Fernando Alonso
rdf:type
ex:fullName
<#TriplesMap1>
rr:logicalTable [ rr:tableName "Student" ];
rr:subjectMap [
rr:template "http://data.example.com/Estudiante/{ID}";
rr:class ex:Estudiante;
];
rr:predicateObjectMap [
rr:predicate ex:fullName;
rr:objectMap [ rr:template "{FirstName} {LastName}" ];
].

8. Background: M-N Relationship
Expected Triples
Student
ID
(PK)
FirstName LastName
10 Venus Williams
11 Fernando Alonso
12 David Villa
Sport
ID
(PK)
Description
110 Tennis
111 Football
112 Formula1
Student_Sport
ID_Student
(PFK)
ID_Sport
(PFK)
10 110
11 111
11 112
12 111
8
<Student/ID=11>
<Sport/ID=111>
<Sport/ID=112>
<Student#hasSport>
<Student#hasSport>

9. Background: 1-N Relationship
Expected Triples
Student
ID
(PK)
FirstName LastName
10 Venus Williams
11 Fernando Alonso
12 David Villa
Sport
ID
(PK)
Description
110 Tennis
111 Football
112 Formula1
Student_Sport
ID_Student
(PFK)
ID_Sport
(PFK)
10 110
11 111
11 112
12 111
Contact
CID
(PK)
SID
(FK)
Email
1 10 venus@hotmail.com
2 10 venus@gmail.com
3 11 fernando@yahoo.com
4 12 david@msn.com
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<Student/ID=10>
<Contact/ID=2>
<Student#hasContact> <Contact/ID=1>
<Student#hasContact>

10. Background: IsA Relationship
Expected Triples
Student
ID
(PFK)
FirstName LastName
10 Venus Williams
11 Fernando Alonso
12 David Villa
Sport
ID
(PK)
Description
110 Tennis
111 Football
112 Formula1
Student_Sport
ID_Student
(PFK)
ID_Sport
(PFK)
10 110
11 111
11 112
12 111
Person
ID
(PK)
SSN
10 1234510
11 1234511
12 1234512
10
<Student/ID=10>
1234510
rdf:type
<Student#SSN>
<Person>

11. Goal
● To automatically generate R2RML mappings
that:
o simulate DM rules
o encodes relationship in database
11
PINKEL, Christoph, et al.
RODI: A Benchmark for Automatic Mapping Generation in
Relational-to-Ontology Data Integration.
Extended Semantic Web Conference 2015

12. MIRROR: Overview
1. Extraction of tables and its relationship
2. Mappings generation
12

13. Pruning Relationship
Types
1 2 3 4 5 6 7 8
Parent (Mand, 1) (Mand, 1) (Mand, 1) (Mand, 1) (Mand, N) (Mand, N) (Mand, N) (Mand, N)
Child (Mand, 1) (Mand, N) (Opt,1) (Opt, N) (Mand, 1) (Mand, N) (Opt,1) (Opt, N)
9 10 11 12 13 14 15 16
Parent (Opt, 1) (Opt, 1) (Opt, 1) (Opt, 1) (Opt, N) (Opt, N) (Opt, N) (Opt, N)
Child (Mand, 1) (Mand, N) (Opt,1) (Opt, N) (Mand, 1) (Mand, N) (Opt,1) (Opt, N)
Reflexive Property
● 2 = 5
● 3 = 9
● 4 = 13
● 7 = 10
● 8 = 14
● 12 = 15
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Primary key is not null
and unique

14. Correspondences between
models
14

15. Mappings Generation
15

16. Implementation & Experimentation
● Implementation
o https://github.com/oeg-upm/MIRROR
o morph-RDB integration
 https://github.com/oeg-upm/morph-rdb
o Any R2RML engine
● Goal
o 1st set mappings -> DM triples
o 2nd mappings -> relationship triples
● Dataset
o W3C DM Testcases
 26 databases (D000 - D025)
o Extension of D011
 1-N
 M-N relationship
 ISA relationship 16

17. D011 Extension
● 1-N
o Student - Contact
● IsA
o Student - Person
17

18. D011: Generated Mappings
1st Set -> DM Triples
18

19. D011 Outputs
DM
19
MIRROR + morph-RDB

20. D011: Generated Mappings
2nd Set -> M-N Relationship
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<Sport/110> <SportHasStudent> <Student/10> .
<Sport/111> <SportHasStudent> <Student/11> .
<Sport/111> <SportHasStudent> <Student/12> .
<Sport/112> <SportHasStudent> <Student/11> .

21. D011 Extension: Generated Mappings
2nd Set -> 1-N Relationship
<Student/10> <StudenthasContact> <Contact/1> .
<Student/10> <StudenthasContact> <Contact/2> .
<Student/11> <StudenthasContact> <Contact/3> .
<Student/12> <StudenthasContact> <Contact/4> .
21

22. D011 Extension: Generated Mappings
2nd Set -> IsA & inherited properties
<Student/10> <rdf:type> <Person> .
<Student/10> <Student#ssn> 1234510 .
<Student/11> <rdf:type> <Person> .
<Student/11> <Student#ssn> 1234511 .
<Student/12> <rdf:type> <Person> .
<Student/12> <Student#ssn> 1234512 . 22

23. Conclusion
● R2RML Mappings Generator
o Implemented as MIRROR
o Integrated with morph-RDB
● 2 Sets of Generated Mappings
o Direct Mapping Triples
o Encoded Relationship in a Database Schema
● Evaluation
o Direct Mapping Test Cases
o Extension of D011
23

24. MIRROR: Automatic R2RML Mapping
Generation from Relational
Databases
Luciano
Frontino de
Medeiros
Freddy Priyatna
Oscar Corcho