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Contextualization: an Abstraction Mechanism for Conceptual Modeling

Contextualization: an Abstraction Mechanism for Conceptual Modeling. Joint work by: Manos Theodorakis Anastasia Analyti Nicolas Spyratos Panos Constantopoulos Institute of Computer Science FORTH-ICS Greece. Outline. Why we need contexts Context definition

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Contextualization: an Abstraction Mechanism for Conceptual Modeling

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  1. Contextualization:an Abstraction Mechanism for Conceptual Modeling Joint work by: Manos Theodorakis Anastasia Analyti Nicolas Spyratos Panos Constantopoulos Institute of Computer Science FORTH-ICS Greece

  2. Outline • Why we need contexts • Context definition • Structuring the contents of a context • Formal Theory • Operations on contexts • Applications • Future Work • Conclusions FORTH-ICS

  3. Different Perceptions Ontology of mechanic for house Different Perceptions Ontology of family for house FORTH-ICS

  4. Other examples of context • Distributed databases • Travel agencies • Anatomical map • Natural language • Ambiguity resolution • Organization of large databases FORTH-ICS

  5. Context features • Viewingthe information from different viewpoints • Support for context-dependent meaning • Viewinginformation at different levels of detail • Modular design • context-dependent reachability • Support for synonyms, homonyms FORTH-ICS

  6. Contextual Ontologies • Organize in a single framework, several contextual representations • Reasoning based on contextual representations FORTH-ICS

  7. Our Definition of Context Context names of o object o reference of o (another context) . . . A context is a set of objects, in which each object is associated with a set of names and (possibly) a reference to an other context. FORTH-ICS

  8. c8 c9 c8 Mountains: o14 Cities: o15 Example c3 Greeece: o0 c1 Dining: o8 Crete, Kriti: o3 Hotels: o9 c0 Athens, Athina: o5 Transportation: o10 c10 Tourist Guide: o1 History: o16 Geography: o2 Map: o4 Geography: o2 c5 c2 c14 Crete: o3 c15 Attiki: o6 c6 Map: o7 • Support for synonyms, homonyms • Object Sharing • Context-dependent naming, referencing • Viewing the information from different viewpoints • Viewing information at different level of detail FORTH-ICS

  9. c2 c1 Crete: o4 15th century: o2 . . . 20th century: o3 Structuring the contents of a context c4 • attr(attr_obj,from,to) • in(in_obj,from,to) • isa(isa_obj,from,to) City: o6 Village: o7 : o11 A: o10 Chandax: o8 Fortification: o9 c5 c3 City: o6 Village: o7 Crete: o4 : o14 . . . B: o12 A: o10 Heraklion: o8 in Airport: o13 FORTH-ICS

  10. Attribution - Contextualization Demographic Data: o1 c1 related to: o4 Persons: o2 Places: o3 c4 c3 c2 born in: o11 Place: o3 Person: o2 Company: o13 located in: o14 Student: o6 Foreign Country: o6 works for: o12 Employee: o7 Domestic Location: o7 no of years: o16 Integer: o15 isa FORTH-ICS

  11. c' name: o6 String: o7 Employee: o3 c name: o6 String: o7 Employee: o3 has dep: o6 Department: o9 Doctor: o4 Nurse: o5 Generalization - Contextualization c0 Organization: o1 Hospital: o2 isa Refinement Relation FORTH-ICS

  12. Classification - Contextualization cd . . . c1 Schema 2: o2 Schema 1: o1 cin . . . . . . Instance 2: o4 Instance 1: o c • The same set of objects can be classified under different schemas • Several set of objects can be classified under the same schema in FORTH-ICS

  13. Context theory • Formal definitions • Model theory • Set of sound & complete inference rules. FORTH-ICS

  14. Formal Definitions Basic Sets O: set of Objects CXT: set of Contexts N : set of Names Reference Paths RPc: set of reference paths starting from the objects of c Contents of a context: cnts(c) Contextualized IB FORTH-ICS

  15. Predicates - Functions Predicates Functions FORTH-ICS

  16. Inference System 1. ISA Reflexivity: 2. ISA Transitivity: 3. Context Refinement: 4. Refinement Reflexivity: 5. Refinement Transitivity: 6. Instance Upward Inheritance: FORTH-ICS

  17. Inference System 7. Inheritance of Built-in Information: 8. Interaction between Generalization-Contextualization: 9. Interaction between Classification-Generalization-Contextualization: FORTH-ICS

  18. Refinement, Equivalence Relations Refinement Relation Equivalence Relation FORTH-ICS

  19. Operations for Creating and Maintaining Contexts • CreateCxt(<contents>) • insert( o, N, c ) • deleteObj( o, c ) • deleteName( o, n, c ) • copyCxt( c ) • deepCopyCxt( c ) • Union • Intersection • Difference FORTH-ICS

  20. c5 Dinos: o1 Head: o2 Nick, Nikos:o4 Context Union InfSys DSS InfSys: o10 Dinos, Xulouris:o1 Head:o2 Nick, Nikos:o4 Dinos: o6 c4 DSS: o20 c5 InfSys: o10 Dinos: o6 c4 DSS: o20 Head:o2 Xilouris:o1 FORTH-ICS

  21. c5 Dinos: o1 Head: o2 Nick, Nikos:o4 Context Intersection InfSys: o10 InfSys DSS Dinos, Xilouris: o1 Head:o2 InfSys: o10 c/5 c4 DSS: o20 Dinos:o1 Dinos : o6 DSS: o20 Head:o2 Head:o2 Xilouris:o1 c/4 Head:o2 Xilouris:o1 FORTH-ICS

  22. Context Difference c4 c4 . . . . . . c5 Dinos: o1 Head: o2 Nick, Nikos:o4 c2 Dinos: o1 InfSys:o10 c'5 AVG: o21 c'1 c6 . . . Nick, Nikos:o4 : o4 DSS: o20 InfSys:o10 c1 Manos View: o1 Dr_Xilouris: o1 : o4 DSS: o20 InfSys:o10 Nicolas View: o2 Manos View y Nicolas View : o4 DSS: o20 InfSys:o10 Manos View: o1 FORTH-ICS

  23. Properties of and A B = B A A B = B A • Commutativity: • Associativity: • Distributivity: (A B) C = A (B C) (A B) C = A (B C) (A B) C = (A C) (B C) (A B) C = (A C) (B C) FORTH-ICS

  24. Constraint: Well-definedness c2 A: o1 c1 A, B: o1 G: o3 A: o2 C: o6 : o3 D: o4 c3 B: o1 E: o5 C: o2 A: o6 • A context is called Well-defined iff: • There is a name path that uniquely identifies each object • recursively contained in the context • Acyclicity Theorem: Closure of well-definedness under Union, Intersection and Difference FORTH-ICS

  25. Applications • Partial View Support • Different people have different views of the same resources • Different applications have different (goal-oriented) models of the same resources • Cooperative work • Workspaces: Private, Group, Public • Ontology Integration/Merging • Web search • Modelling of user interests/Reply based on query context FORTH-ICS

  26. Applications (cont.)Pervasive computing • Agent context • Redefined contexts of agent situations • Central Manager • Collects Agent Contexts • Reasons about them • Maintains consistency FORTH-ICS

  27. Future Work • Extension of the web ontology languages RDF and OWL with contexts • Querying and reasoning with: • contextualized RDF • contextualized OWL FORTH-ICS

  28. Conclusions • A formal notion of context in information modeling • Formal definition • Core axioms • Operations • Supported features • Partial views • Relative semantics • Modular design FORTH-ICS

  29. Thank you! FORTH-ICS

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