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Property-based Access of RDF Data

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Property-based Access of RDF Data

  1. 1. Web Science & Technologies University of Koblenz ▪ Landau, GermanyProperty-based Typing for RDF-Access – A Vision – Stefan Scheglmann Gerd Gröner
  2. 2. Publishing Linked Data on the Web - Status1. Huge collections of openand governmental data arepublished as Linked Data representation formalism?2. Data enrichment  Meta data  Micro formatsfor semantic search andexplorationWeST Gerd Gröner PSW 2012 groener@uni-koblenz.de 2
  3. 3. … the Technology: RDF and Linked DataRDFData model with formal semantics Flexible data representation Extendable Deal with incomplete dataLinked DataBest practice to publish structured data on the web Observation: successful publishing and exploration of data on the WebWeST Gerd Gröner PSW 2012 groener@uni-koblenz.de 3
  4. 4. What is the problem?➔ The flexible data model makes it difficult for applications to access the data API • Type system Class • Fixed data schema - properties data access RDF • Missing type statements • Incomplete information • Changing data • Heterogeneous dataWeST Gerd Gröner PSW 2012 groener@uni-koblenz.de 4
  5. 5. Example - Scenario Users: (Accounts, available user data) Platform user data e-participation access platform Facebook LinkedIn ... - read user data - send news -…WeST Gerd Gröner PSW 2012 groener@uni-koblenz.de 5
  6. 6. Examplealice rdf:type ex:citizen. API with methods:bob rdf:type ex:citizen.dave rdf:type ex:citizen.eric rdf:type ex:citizen. Send mail to all citizen with name and mbox!alice foaf:name "Alice". → Candy?alice foaf:mbox "alice@home.com".alice foaf:interest<http://wikipedia.org/Literature>. Modify/read interest of allbob foaf:name "Bob". citizen!bob foaf:mbox "bob@mail.com". → Dave?bob foaf:interest<http://wikipedia.org/Cinema>.candy foaf:name "Candy".candy foaf:mbox "candy@coldmail.com".dave foaf:name "Dave".dave foaf:mbox "dave@online.com".WeST Gerd Gröner PSW 2012 groener@uni-koblenz.de 6
  7. 7. Example (2)alice rdf:type ex:citizen. API with methods:bob rdf:type ex:citizen.dave rdf:type ex:citizen.eric rdf:type ex:citizen.alice foaf:name "Alice".alice foaf:mbox "alice@home.com".alice foaf:interest<http://wikipedia.org/Literature>.eric foaf:name "Eric". Find interest oferic ex:member citizen!<http://cinemafriends.com>. → Eric?<http://cinemafriends.com> ex:interest <http://wikipedia.org/Cinema>.WeST Gerd Gröner PSW 2012 groener@uni-koblenz.de 7
  8. 8. How should a solution look like?API with methods: There might be missing type statements Send mail to all citizen ➔ access data based on properties with name and mbox! → Candy? (e.g., to define methods)s There might be missing properties Modify/read interest of all citizen! ➔ access data with → Dave?  Required and  optional properties There might be implicit properties. Find interest of citizen! ➔ access data with properties that are → Eric? derived (by reasoning or navigation) WeST Gerd Gröner PSW 2012 groener@uni-koblenz.de 8
  9. 9. OutlineHow to achieve a possible solution? 1. Object Triple mappingWeST Gerd Gröner PSW 2012 groener@uni-koblenz.de 9
  10. 10. Mapping Triples to ObjectsBackground: object relational mappingDesign patterns: Domain mapper RDB Model Application development language data Example: Class to table Citizen name mapper RDB mbox - class to table - table columns to attributes - foreign key to object relations - every tuple to an objectWeST Gerd Gröner PSW 2012 groener@uni-koblenz.de 10
  11. 11. Map Triples to Objects (2)Basic Idea1. Define a class for each type Citizen Topic2. Triples to objects alice - resources to objects bob cinema - predicates to attributes or relations citizen alice bob cinema WeST Gerd Gröner PSW 2012 groener@uni-koblenz.de 11
  12. 12. Map Triples to Objects (3)… but does this solve the problem? access1. We need types for classes. ? Citizen candy alice bob2. We can not state properties as optionalWeST Gerd Gröner PSW 2012 groener@uni-koblenz.de 12
  13. 13. Outline How to achieve a possible solution? 1. Object Triple mapping 2. Class definitions like in OWLWeST Gerd Gröner PSW 2012 groener@uni-koblenz.de 13
  14. 14. Expressive Class DefinitionsConstructs for property specifications of classes … does this solve our problem?➔ not possible in RDF➔ not realized in Linked DataWeST Gerd Gröner PSW 2012 groener@uni-koblenz.de 14
  15. 15. OutlineHow to achieve a possible solution? 1. Object Triple mapping 2. Class definitions like in OWL 3. Extract schemaWeST Gerd Gröner PSW 2012 groener@uni-koblenz.de 15
  16. 16. Schema Extraction and Type Provider➔ 1. Step: Derive schemaSchema is based on property statements group instances that share some properties schema extraction RDF dataWeST Gerd Gröner PSW 2012 groener@uni-koblenz.de 16
  17. 17. Schema Extraction and Type Provider2. Step: Use Type Provider component that provides types, properties, and methods in programs • i.e., programmers get type information of entities (like databases) they work with F# offers built-in type providers and allows user defined providers … does this solve our problem?➔ Schema is a snapshotWeST Gerd Gröner PSW 2012 groener@uni-koblenz.de 17
  18. 18. Outline How to achieve a possible solution? 1. Object Triple mapping 2. Class definitions like in OWL 3. Extract schema How should a solution look like?WeST Gerd Gröner PSW 2012 groener@uni-koblenz.de 18
  19. 19. Requirements for a solutionProperty-based Types: - name - mbox - hierarchies - specialization - name - name - mbox - mbox - interest - phone - name - mbox - interest - memberWeST Gerd Gröner PSW 2012 groener@uni-koblenz.de 19
  20. 20. Requirements for a solution (2)Flexible Type System - name - mbox➔ Extendable - name - name - mbox OR - mbox web - phone - interest - skypeWeST Gerd Gröner PSW 2012 groener@uni-koblenz.de 20
  21. 21. Requirements for a solution (3)Inference:➔ Derive properties➔ Derive type - name - mbox - interest Group - name member - interest - mboxWeST Gerd Gröner PSW 2012 groener@uni-koblenz.de 21
  22. 22. Current Status … or the trade-off between persistent data access and flexible representation Build on types and Incomplete and flexible extracted schema RDF data representation • Object Triple mapping • Missing type statements • Class specifications (for • Property-centric incomplete data) • Extendable • Schema extraction and type provider (e.g., F#) … how to bring these “worlds” together?WeST Gerd Gröner PSW 2012 groener@uni-koblenz.de 22
  23. 23. Outline How to achieve a possible solution? 1. Object Triple mapping 2. Class definitions like in OWL 3. Extract schema How should a solution look like? Our vision / statementWeST Gerd Gröner PSW 2012 groener@uni-koblenz.de 23
  24. 24. Statement New Programming Paradigm: “Property-based typing for RDF data access” Basic idea: API - specify operations Data “Typing” Traits: Types (incomplete) + Set of propertiesWeST Gerd Gröner PSW 2012 groener@uni-koblenz.de 24
  25. 25. Example (Property-based Access)alice rdf:type ex:citizen.bob rdf:type ex:citizen.dave rdf:type ex:citizen. Traits: - foaf:mboxalice foaf:name "Alice". - foaf:namealice foaf:mbox "alice@home.com".alice foaf:interest <http://wikipedia.org/Literature>bob foaf:name "Bob".bob foaf:mbox "bob@mail.com".bob foaf:interest <http://wikipedia.org/Cinema>candy foaf:name "Candy".candy foaf:mbox "candy@coldmail.com".dave foaf:name "Dave".dave foaf:mbox "dave@online.com".WeST Gerd Gröner PSW 2012 groener@uni-koblenz.de 25
  26. 26. Conclusion … Discussion New Programming Paradigm: “Property-based typing for RDF data access”  What are the challenges in a property-based approach for programming the semantic Web? Which are the implications that solutions of these challenges could have?WeST Gerd Gröner PSW 2012 groener@uni-koblenz.de 26
  27. 27. Discussion: ChallengesType hierarchies (property-based):1. How to build a reliable type hierarchy based on property sets? i. Schema extraction ii. Formal concept analysis (for occurring property combinations)2. How to combine property-based types and type statements (rdf:type)?WeST Gerd Gröner PSW 2012 groener@uni-koblenz.de 27
  28. 28. Discussion: Challenges (2)Incompleteness1. How to interpret a missing property? ➔ Missing or unknown?2. How to achieve type inference (like in RDFS)?WeST Gerd Gröner PSW 2012 groener@uni-koblenz.de 28
  29. 29. Discussion: Challenges (3)Contracts➔ Method and type contracts (based on property sets)1. How to declare optional and required properties?2. Can we support global and local contracts?WeST Gerd Gröner PSW 2012 groener@uni-koblenz.de 29

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