1. Ontology-Based Data Mediation for Semantic Environments PhD Thesis Defense Candidate: Adrian Mocan Supervisor: Prof. Dr. Manfred Hauswirth National University of Ireland, Galway, Ireland 3 rd of July, 2008

2. National University of Ireland, Galway 2 Overview Context and Motivation Formal Model for Mappings Creation Design-time Ontology Mapping Run-time Data Mediation Evaluation Conclusions

3. National University of Ireland, Galway 3 Motivation and Context Semantic Web Services Semantic Execution Environment Enable the discovery, selection, composition, invocation of Web Services Different ontologies might be used in describing services offered by different providers Mediation required during the discovery, invocation Data mediation solutions are required

4. National University of Ireland, Galway 4 Problem Definition Instance Transformation scenario

5. National University of Ireland, Galway 5 Solution Design-time / Run-time Separation Formal Model Software implementations have been developed

6. National University of Ireland, Galway 6 Formal Model Main Contributions Formal Model for the mapping creation Ontology language independent model Formalizing the main concepts behind both the design-time and run-time phases Algorithms and methods are expressed in terms of this model Can be applied to approaches targeting other ontology models/languages Inherited by the grounding of the model to the same ontology model

7. National University of Ireland, Galway 7 Abstract Elements Items Primitive Items Compound Items Description Items Relationships describes Description Item Compound Item successor Description Item Successor Item Primitive Item Compound Item Primitive Item Compound Item Description Item describes Successor Item successor Entities described by other entities is a Successor Items x.(ci(x) y.(di(y) ٨ describes(y, x))) (1) x. y.(describes(x, y) => ci(y) ٨ di(x)) (2) x.(di(x) y.(si(y) ٨ successor(y, x))) (3) x. y.(successor(x, y) => di(y) ٨ si(x)) (4) x.(si(x) => pi(x) ci(x))) (5) x.( (ci(x) ٨ pi(x))) (6) x.( (ci(x) ٨ di(x))) (7) x.( (pi(x) ٨ di(x))) (8) x.(ci(x) y.(di(y) ٨ describes(y, x))) (1) x. y.(describes(x, y) => ci(y) ٨ di(x)) (2) x.(di(x) y.(si(y) ٨ successor(y, x))) (3) x. y.(successor(x, y) => di(y) ٨ si(x)) (4) x.(si(x) => pi(x) ci(x))) (5) x.( (ci(x) ٨ pi(x))) (6) x.( (ci(x) ٨ di(x))) (7) x.( (pi(x) ٨ di(x))) (8)

8. National University of Ireland, Galway 8 Perspectives and Contexts [1] Perspectives Contexts

9. National University of Ireland, Galway 9 Perspectives and Contexts [2] successor CI_1 DI_11 CI_2 describes successor CI_2 DI_21 PI_2 describes successor DI_22 CI_3 describes successor CI_3 DI_31 PI_1 describes PI_2 PI_1 Perspective = Context 0 Context n

10. National University of Ireland, Galway 10 Mapping Operation Mapping Context: Operation: Contexts update Creation of mappings Depends on the chosen x and y Depends on the perspectives Depends on the current contexts

11. National University of Ireland, Galway 11 successor CI_1 DI_11 CI_2 describes successor CI_2 DI_21 PI_2 describes successor DI_22 CI_3 describes successor CI_3 DI_31 PI_1 describes PI_2 PI_1 Decomposition Context 0 successor CI_2 DI_21 PI_2 describes successor DI_22 CI_3 describes Decomposition Decomposition and Contexts Context 1 successor CI_3 DI_31 PI_1 describes Context 2 successor CI_2 DI_21 PI_2 describes successor DI_22 CI_3 describes Context 1 Decomposition

12. National University of Ireland, Galway 12 Design-time Ontology Mapping First phase of the mediation solution Human-driven activity Produces a set of mappings (i.e. an alignment between two ontologies)

13. National University of Ireland, Galway 13 Design-time Ontology Mapping Main Contributions Design-time Ontology Mapping Based on the Formal Model New techniques able to enhance the semi- automatic aspect of ontology mapping Ontology perspectives Decomposition and Mapping Contexts Top-down and Bottom-up mapping strategies Implementation of these techniques as part of a mapping tool

14. National University of Ireland, Galway 14 Ontology Perspectives [1] Semi-automatic methods involve graphical tools and techniques for ontology visualization Depending of the visualization technique on the ontology certain mismatches become easier/harder to address The perspectives or the view-points adopted to visualize the source and the target ontologies play a crucial role

15. National University of Ireland, Galway 15 Ontology Perspectives [2] Each ontology perspective involves one instantiation of the model

16. National University of Ireland, Galway 16 Ontology Perspectives [3] concept person name ofType _string age ofType _integer hasGender ofType gender hasChild ofType person marriedTo ofType person concept gender value ofType _string instance male memberOf gender value hasValue "male instance female memberOf gender value hasValue "female" concept human name ofType _string age ofType _integer noOfChildren ofType _integer concept man subConceptOf human concept woman subConceptOf human concept marriage hasParticipant ofType human date ofType _date Source Ontology Target Ontology

17. National University of Ireland, Galway 17 Ontology Perspectives [3] string integer date human name string age integer noOfChildren integer man name string age integer noOfChildren integer woman name string age integer noOfChildren integer marriage hasParticipant human date date Source Ontology Target Ontology string integer person name string age integer hasGender gender hasChild person marriedTo person gender value string PartOf pi data types, concepts without attributes ci concepts with attributes di attributes

18. National University of Ireland, Galway 18 Ontology Perspectives [3] string integer person hasGender male:gender hasGender female:gender gender string integer human man woman marriage Source OntologyTarget Ontology InstanceOf di attributes that can be filled by constants (afc) included in the ontology ci concepts with at least one afc pi data types, concepts without any afc-s

19. National University of Ireland, Galway 19 Ontology Perspectives [3] string integer date person gender name hasDomain person hasRange string age hasDomain person hasRange integer... marriedTo hasDomain person hasRange person value hasDomain gender hasRange string string integer date human name string age integer noOfChildren integer man name string age integer noOfChildren integer woman name string age integer noOfChildren integer marriage hasParticipant human date date Source Ontology Target Ontology RelatedBy PartOf pi concepts ci attributes di {hasDomain, hasRange}

20. National University of Ireland, Galway 20 Implementing Perspectives Each role (i.e. items) have to be filled by an ontological entity Each relationship has to be defined (i.e. describes, successor) Define what kind mappings can be created using combination of these perspectives Three perspectives defined in this thesis PartOf, InstanceOf, RelatedBy Two of them fully implemented in the mapping tool

21. National University of Ireland, Galway 21 Decomposition and Context [1] Not all the information contained in the perspective is needed in a given step By isolating the domain experts from the unnecessary information they can better concentrate on their tasks

22. National University of Ireland, Galway 22 Decomposition and Context [2]

23. National University of Ireland, Galway 23 Top-Down and Bottom-Up Mapping Strategies Bottom-Up Start from the simple entities to be mapped Continue with more complex ones Top-Down Start from what is of interest to be mapped in the two ontologies The semi-automatic support guides the next steps Employ two aspects of the semi-automatic support Suggestion Algorithms Decomposition and context These two strategies can be combined

24. National University of Ireland, Galway 24 Ontology Mappings Abstract representation of mappings Alignment format developed as part of the KW [ESS06] Schema elements (e.g. concepts, attributes) Restriction on the schema elements (e.g. allowed values for an attribute) Concept2Concept ( C2C ) Attribute2Attribute ( A2A ) Concept2Attribute ( C2A ) Attribute2Concept ( A2C ) mapping(sourceEntity; [sourceEntityRestriction]; targetEntity; [targetEntityRestriction]; typeOfMapping) [ESS06] J. Euzenat, F. Scharffe, and L. Serafini. Specification of the alignment format. Knowledge Web Deliverable D2.2.6, 2006.

25. National University of Ireland, Galway 25 Design-time Ontology Mapping Summary Allows the semi-automatic creation of mappings between a Source and a Target Ontology Goals Graphical interface Set of mechanisms towards semi-automatic creation of mappings Capturing the semantic relationships identified in the process Storing these mappings in a persistent storage Output Abstract representation of the mappings

26. National University of Ireland, Galway 26 Run-time Data Mediation Second phase of the mediation solution Once the mappings are available they can be used to do data mediation Mappings need to be prepared for a mediation scenario and executed

27. National University of Ireland, Galway 27 Run-time Data Mediation Main Contributions Main Contributions Engine implemented on top of a generic rule-reasoner Decoupling between abstract representation of mappings and their executable representation Grounding of the abstract representation 1 to F-Logic Dynamic generation of rules based on the heterogeneous data to be mediated 1 The abstract representation of mappings is not part of the work in this thesis

28. National University of Ireland, Galway 28 Run-time Phase [1] Grounding the abstract mappings Associate a formal semantics to the mappings Obtain rules in a concrete language Why not at design time? Offers a grater flexibility Different groundings for the same mappings set Different execution environments for the grounded mappings Easier to maintain the abstract mappings Important point of alignment Caching mechanism can be used

29. National University of Ireland, Galway 29 Run-time Phase [2] Main Mediation Scenario: Instance Transformation Inputs Mappings Incoming data Source ontology instances Features Completely automatic process Grounding of the abstract mappings to a concrete language F-Logic, WSML-Rule Relies on reasoner to evaluate the mapping rules Outputs Mediated data Target ontology instances

30. National University of Ireland, Galway 30 Evaluation Implicit evaluation Tools have been implemented based on the conceptual ideas Applied on show-cases in European projects (DIP, SemanticGov, SEEMP, SUPER)

31. National University of Ireland, Galway 31 Evaluation SEEMP Project 3 ontology sets ARL: 323 Concepts, 296 Axioms EURES: 425 Concepts, 395 Axioms Reference Ontology: 485 Concepts, 13 Axioms Total No. of Rules Required No. of Rules Grounding Time Creating KB Time Querying KB Time Cleaning Results Time Total Time EURES RO (22 Inst) 1048499172ms7828ms78ms15ms8140ms RO TELMI (23 Inst) 91334447ms5453ms94ms15ms5609ms EURES TELMI (20 Inst) 167715746ms3454ms109ms16ms3657ms Simple Ex. (7 inst) 29270ms266ms31ms0ms297ms

32. National University of Ireland, Galway 32 Evaluation Implicit evaluation Tools have been implemented based on the conceptual ideas Applied on show-cases in European projects (DIP, SemanticGov, SEEMP, SUPER) Explicit evaluation Ontology Mapping Tool Comparison MAFRA, PROMPT Formal Model evaluation Measures from conceptual and reference modeling

33. National University of Ireland, Galway 33 Conclusions Ontology-based Data Mediation Solution New methods for enhancing the machine support during the mapping process Focuses on Instance transformation scenario Provides on ontology language independent formal model Formal and reusable definition of several strategies and methods for semi-automatic mappings creation Software implementation of the main conceptual ideas

34. National University of Ireland, Galway 34 Thank you for your attention! Q&A

35. National University of Ireland, Galway 35 Back-up Slides

36. National University of Ireland, Galway 36 Formal Model

37. National University of Ireland, Galway 37 The Formal model can be used in assessing the quality of mappings From the Instance Transformation scenario point of view Completeness of Mappings Complete Mappings for the Source Data Complete Mappings for the Target Data Quality Analysis of Mappings [1]

38. National University of Ireland, Galway 38 Quality Analysis of Mappings [2] Containment of Mappings Maximality of Data Structures

39. National University of Ireland, Galway 39 Design-time Phase

40. National University of Ireland, Galway 40 primitive_concept (data type) compound_concept attribute1 primitive_concept attribute2 compound_concept PartOf Perspective primitive_item compound_item hasDescription1 primitive_item hasDescription2 compound_item primitive_item compound_item hasDescription1 primitive_item hasDescription2 compound_item primitive_concept (data type) compound_concept attribute1 primitive_concept attribute2 compound_concept

41. National University of Ireland, Galway 41 primitive_concept (data type) compound_concept attribute1 primitive_concept attribute2 compound_concept PartOf to PartOf Mappings primitive_item compound_item hasDescription1 primitive_item hasDescription2 compound_item primitive_item compound_item hasDescription1 primitive_item hasDescription2 compound_item primitive_concept (data type) compound_concept attribute1 primitive_concept attribute2 compound_concept class to class mapping (classMapping)

42. National University of Ireland, Galway 42 primitive_concept (data type) compound_concept attribute1 primitive_concept attribute2 compound_concept PartOf to PartOf Mappings primitive_item compound_item hasDescription1 primitive_item hasDescription2 compound_item primitive_item compound_item hasDescription1 primitive_item hasDescription2 compound_item primitive_concept (data type) compound_concept attribute1 primitive_concept attribute2 compound_concept class to class mapping (classMapping) attribute to attribute mapping (attributeMapping)

43. National University of Ireland, Galway 43 primitive_concept (data type) compound_concept attribute1 primitive_concept attribute2 compound_concept PartOf to PartOf Mappings primitive_item compound_item hasDescription1 primitive_item hasDescription2 compound_item primitive_item compound_item hasDescription1 primitive_item hasDescription2 compound_item primitive_concept (data type) compound_concept attribute1 primitive_concept attribute2 compound_concept class to class mapping (classMapping) class to attribute mapping (classAttributeMapping)

44. National University of Ireland, Galway 44 primitive_concept (data type) compound_concept attribute1 primitive_concept attribute2 compound_concept PartOf to PartOf Mappings primitive_item compound_item hasDescription1 primitive_item hasDescription2 compound_item primitive_item compound_item hasDescription1 primitive_item hasDescription2 compound_item primitive_concept (data type) compound_concept attribute1 primitive_concept attribute2 compound_concept class to class mapping (classMapping) class to attribute mapping (classAttributeMapping)

45. National University of Ireland, Galway 45 InstanceOf Perspective primitive_item compound_item hasDescription1 primitive_item hasDescription2 compound_item primitive_item compound_item hasDescription1 primitive_item hasDescription2 compound_item regular_concept instance_concept attribute1 regular_concept attribute2 instance_concept regular_concept instance_concept attribute1 regular_concept attribute2 instance_concept

46. National University of Ireland, Galway 46 InstanceOf to InstanceOf Mappings primitive_item compound_item hasDescription1 primitive_item hasDescription2 compound_item primitive_item compound_item hasDescription1 primitive_item hasDescription2 compound_item regular_concept instance_concept attribute1 regular_concept attribute2 instance_concept regular_concept instance_concept attribute1 regular_concept attribute2 instance_concept class to class mapping (classMapping)

47. National University of Ireland, Galway 47 InstanceOf to InstanceOf Mappings primitive_item compound_item hasDescription1 primitive_item hasDescription2 compound_item primitive_item compound_item hasDescription1 primitive_item hasDescription2 compound_item regular_concept instance_concept attribute1 regular_concept attribute2 instance_concept regular_concept instance_concept attribute1 regular_concept attribute2 instance_concept class to class mapping (classMapping) attribute to attribute mapping (attributeMapping) 2*attributeValueCondition(valueCondition)

48. National University of Ireland, Galway 48 InstanceOf to InstanceOf Mappings primitive_item compound_item hasDescription1 primitive_item hasDescription2 compound_item primitive_item compound_item hasDescription1 primitive_item hasDescription2 compound_item regular_concept instance_concept attribute1 regular_concept attribute2 instance_concept regular_concept instance_concept attribute1 regular_concept attribute2 instance_concept class to class mapping (classMapping) class to attribute mapping (classAttributeMapping) AttributeTypeCondition

49. National University of Ireland, Galway 49 concept attribute hasDomain concept hasRange concept RelatedBy Perspective primitive_item compound_item hasDescription1 primitive_item hasDescription2 compound_item primitive_item compound_item hasDescription1 primitive_item hasDescription2 compound_item concept attribute hasDomain concept hasRange concept

50. National University of Ireland, Galway 50 concept attribute hasDomain concept hasRange concept RelatedBy to RelatedBy Mappings primitive_item compound_item hasDescription1 primitive_item hasDescription2 compound_item primitive_item compound_item hasDescription1 primitive_item hasDescription2 compound_item concept attribute hasDomain concept hasRange concept attribute to attribute mapping (attributeMapping)

51. National University of Ireland, Galway 51 concept attribute hasDomain concept hasRange concept RelatedBy to RelatedBy Mappings primitive_item compound_item hasDescription1 primitive_item hasDescription2 compound_item primitive_item compound_item hasDescription1 primitive_item hasDescription2 compound_item concept attribute hasDomain concept hasRange concept attribute to attribute mapping (attributeMapping) class to class mapping (classMapping)

52. National University of Ireland, Galway 52 Top-Down and Bottom-Up Mapping Strategies [2] Bottom-Up Advantages Better suggestions since the lexical algorithms tend to return better results when no structure is present Disadvantages Domain experts has to discover by themselves the elements to be mapped Top-Down Advantages Decomposition and contexts offer guidance and support in identifying the elements that need to be mapped Disadvantages Lower suggestions quality Structural algorithms rely on the already created mappings These two strategies can be combined

53. National University of Ireland, Galway 53 Implementation http://sourceforge.net/projects/wsmt/ http://sourceforge.net/projects/wsmx/

54. National University of Ireland, Galway 54 Implementation [2] WSMO ooMediator ooMediator _"http://.../ontologyMediator … source _"http://.../sourceOntology target _"http://.../targetOntology hasMediationService _"http://.../datamediator webService _"http://.../datamediator … capability … interface … … WSDL Web Service WSMO Semantic Web Service

55. National University of Ireland, Galway 55 Run-time Phase

56. National University of Ireland, Galway 56 Running Examples concept Person hasChristianName ofType _string hasSurname ofType _string hasGender ofType Gender dateOfBirth ofType Date concept Date day ofType _integer month ofType _integer year ofType _integer concept Gender instance _1 memberOf Gender instance _2 memberOf Gender instance _ memberOf Gender concept Citizen hasName ofType Name hasSex ofType Sex hasBirthday ofType Date concept Name hasFirstName ofType _string hasSurname ofType _string concept Date day ofType _integer month ofType _integer year ofType _integer concept Sex instance M memberOf Sex instance F memberOf Sex instance N memberOf Sex Source Ontology Target Ontology

57. National University of Ireland, Galway 57 Mapping Rules in WSML Class to Class Mapping mapping(o1#Person, o2#Citizen, C2C) mediated(?x, o2#Citizen) memberOf o2#Citizen and mapped(o1#Person, o2#Citizen,?x):- ?x memberOf o1#Person instance johnS memberOf o1#Person mediated(johnS, o2#Citizen) memberOf o2#Citizen mapped(o1#Person, o2#Citizen, johnS)

58. National University of Ireland, Galway 58 Mapping Rules in WSML Class to Attribute Mappings mapping( o1#Person, o2#Citizen.hasName, C2A) mediated(?x,o2#Citizen)[hasName hasValue mediated(?x, o2#Name)] memberOf o2#Citizen:- ?x memberOf o1#Person and mediated(?x,o2#Name)[?anAttribute hasValue ?aValue] memberOf o2#Name. instance johnS memberOf o1#Person mediated(?x,o2#Name)[…] memberOf o2#Name mediated(johnS,o2#Citizen)[hasName hasValue mediated(johnS, o2#Name)] memberOf o2#Citizen

59. National University of Ireland, Galway 59 Mapping Rules in WSML Attribute to Attribute Mappings (1) mapping(o1#Person.hasSurname, o2#Name.hasSurname, A2A) mediated(?x,o2#Name)[hasSurname hasValue ?v] memberOf o2#Name:- ?x[hasSurname hasValue ?v] memberOf ?subCs and ?subCs subConceptOf o1#Person and mapped(?subCs,o2#Name,?x). instance johnS[hasSurname hasValue Smith] memberOf o1#Person mapped(o1#Person, o2#Name, johnS) mediated(johnS,o2#Name)[hasSurname hasValue Smith] memberOf o2#Name mapping(o1#Person, o2#Name, C2C )

60. National University of Ireland, Galway 60 Mapping Rules in WSML Attribute to Attribute Mappings (2) mapping(o1#Person.dateOfBirth, o2#Citizen.hasBirthDay, A2A) mediated(?x,o2#Citizen)[hasBirthDay hasValue mediated(?i, o2#Date)] memberOf o2#Citizen:- ?x[dateOfBirth hasValue ?i] memberOf ?subCs and ?subCs subConceptOf o1#Person and mapped(?subCs, o2#Citizen) mediated(?i,o2#Date)[?anAttribute hasValue ?aValue]. instance johnS[dateOfBirth hasValue johnS_birthdate] memberOf o1#Person mapped(o1#Person, o2#Citizen, johnS) mediated(johnS_birthdate, o2#Date)[...] mediated(johnS,o2#Citizen)[hasBirthDay hasValue mediated(johnS_birthdate, o2#Date)] memberOf o2#Citizen

61. National University of Ireland, Galway 61 Mapping Rules in WSML Attribute to Class Mappings

62. National University of Ireland, Galway 62 Mapping Conditions Conditions that have to hold for the mapping to apply Three main types Attribute occurrence conditions Attribute type conditions Attribute value conditions Source Target

63. National University of Ireland, Galway 63 Querying and Retrieving the Mediated Instances ?- ?x memberOf o2#Citizen Found result to the query: (1) -- ?x = mediated(johnS, o2#Citizen) ?- mediated(johnS, o2#Citizen)[?y hasValue ?z] memberOf o2#Citizen and ?z memberOf ?avC. Found results to the query: (1) -- ?z = o2#M, ?avC = o2#Sex, ?y=o2#hasSex (2) -- ?z = mediated(johnS,o2#Name), ?avC = o2#Name, ?y= o2#hasName (3) -- ?z = mediated(johnS_birthDate, o2#Date), ?avC = o2#Date, ?y = o2#hasBirthday ?- mediated(johnS, o2#Name)[?y hasValue ?z] memberOf o2#Name and ?z memberOf ?avC. Found results to the query : (1) -- ?z = John, ?avC = string, ?y = o2#hasFirstName (2) -- ?z = Smith, ?avC = string, ?y = o2#hasSurname...

64. National University of Ireland, Galway 64 Evaluation

65. National University of Ireland, Galway 65 Evaluation [2] Explicit evaluation Design-time Ontology Mapping and Run-time Data Mediation By comparing the tools with MAFRA and PROMPT

66. National University of Ireland, Galway 66 Evaluation [2]

67. National University of Ireland, Galway 67 Evaluation [2]

68. National University of Ireland, Galway 68 Evaluation [3] Measurements of the suggestion algorithms in conjunction with decomposition and context updates

69. National University of Ireland, Galway 69 Evaluation [5] Formal Model Evaluations Conceptual Modeling Reference Modeling Completeness, Adaptability, Extensibility, Usability, Re-usability, Acceptance