Querying Trust
in RDF Data with
    tSPARQL
                         Olaf Hartig
        http://olafhartig.de/foaf.rdf#olaf
●   The Semantic Web is a reality
     ●   Large amount of semantically interlinked data
     ●   Applications emerge




...
Is the data
                  trustworthy?

Olaf Hartig - Querying Trust in RDF Data with tSPARQL   3
SELECT ?hotel ?hotelName
     WHERE {
       ?hotel rdf:type   umbel:HotelBuilding ;
              p:location dbpedia:Hera...
SELECT ?hotelName ?reviewText
   WHERE {
      ?hotel rdf:type          umbel:HotelBuilding ;
                p:location d...
Outline

             Trust model
             for RDF data


                                                            ...
Trustworthiness of RDF Data
 ●   The trustworthiness of RDF statements is the subjective
     belief or disbelief in the t...
Atomic Trust
 ●   A trust function associates single RDF statements with a
     subjective trust value.
                  ...
Aggregated Trust
 ●   A trust aggregation function calculates an aggregated
     trust value for a trust weighted RDF grap...
Outline

             Trust model
             for RDF data


                                                            ...
Trust-aware query processing


 ●   SPARQL does not consider trust values
 ●   Basic idea:
     ●   Extend the notion of s...
Basic graph pattern matching

  <http://.../data/KnossosRoyal> rev:hasReview
                                             ...
Basic graph pattern matching

  <http://.../data/KnossosRoyal> rev:hasReview
                                             ...
Basic graph pattern matching

  <http://.../data/KnossosRoyal> rev:hasReview
                                             ...
Basic graph pattern matching

  <http://.../data/KnossosRoyal> rev:hasReview
                                             ...
Basic graph pattern matching

  <http://.../data/KnossosRoyal> rev:hasReview
                                             ...
Basic graph pattern matching

  <http://.../data/KnossosRoyal> rev:hasReview
                                             ...
Trust-aware query processing


 ●   SPARQL does not consider trust values
     Basic idea:
                               ...
Redefining the SPARQL algebra
 {
     {
         ?h rdf:type umbel:HotelBuilding ;
            p:location dbpedia:Heraklio...
Redefining the SPARQL algebra


                                                                                 µ
       ...
Redefining the SPARQL algebra


                                                                                  µ       ...
Redefining the SPARQL algebra
 ●   A trust merge function calculates a merged trust value for
     two trust weighted solu...
Basic idea


 ●   SPARQL does not consider trust values
     Basic idea:
                                      √
 ●


    ...
Evaluation
         ●         tSPARQL query engine (extension of SPARQL engine ARQ)
         ●         Berlin SPARQL Bench...
Evaluation
           ●            Simple provenance-based trust function
                      ●         Assumes existenc...
Outline

             Trust model
             for RDF data


                                                            ...
Evaluating trust requirements
 ●   Goal: ensuring a certain trustworthiness for the solutions
           of a specific gra...
Evaluating trust requirements
 ●   Goal: ensuring a certain trustworthiness for the solutions
           of a specific gra...
Evaluating trust requirements

                                                        Join

 {
     { ?h rdf:type umbel:H...
Evaluating trust requirements

                                                        Join

 {
     { ?h rdf:type umbel:H...
Evaluating trust requirementsµ                                                                           t
               ...
Evaluating trust requirementsµ                                                                           t
               ...
Evaluating trust requirementsµ                                                                              t
            ...
Evaluating trust requirementsµ
         µ         t                                                                       ...
Evaluating trust requirementsµ
         µ         t                                                                       ...
Accessing trust values
 ●   Goal: accessing the trust value for the solution of a
           specific graph pattern



   ...
Accessing trust values
 ●   Goal: accessing the trust value for the solution of a
           specific graph pattern
 ●   A...
Outline

             Trust model
             for RDF data


                                                            ...
Rewrite Rules
 ●   Rewriting algebra expressions to improve query execution
 ●   E.g., for join operators that employ
    ...
Evaluation
                   ●                     Equivalent BSBM-based setup with 6 tSPARQL queries
                   ...
Take-away summary
                                                         Trust model
                                   ...
These slides have been created by
                                      Olaf Hartig

                                     ...
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Querying Trust in RDF Data with tSPARQL

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With these slides I presented my paper on "Querying Trust in RDF Data with tSPARQL" at the European Semantic Web Conference 2009 (ESWC) in Heraklion, Crete. Actually, this slideset is an extended version of the slides I used for the talk (more examples and evaluation).

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Querying Trust in RDF Data with tSPARQL

  1. 1. Querying Trust in RDF Data with tSPARQL Olaf Hartig http://olafhartig.de/foaf.rdf#olaf
  2. 2. ● The Semantic Web is a reality ● Large amount of semantically interlinked data ● Applications emerge Olaf Hartig - Querying Trust in RDF Data with tSPARQL 2
  3. 3. Is the data trustworthy? Olaf Hartig - Querying Trust in RDF Data with tSPARQL 3
  4. 4. SELECT ?hotel ?hotelName WHERE { ?hotel rdf:type umbel:HotelBuilding ; p:location dbpedia:Heraklion ; rdfs:label ?hotelName . TRUST AS ?t } ORDER BY ?t Returns a list of hotels in Heraklion ordered by the trustworthiness of the data. Olaf Hartig - Querying Trust in RDF Data with tSPARQL 4
  5. 5. SELECT ?hotelName ?reviewText WHERE { ?hotel rdf:type umbel:HotelBuilding ; p:location dbpedia:Heraklion ; rdfs:label ?hotelName . { ?hotel rev:hasReview ?review . ?review rev:text ?reviewText . SELECT ?hENSURE TRUST ( 0.7 , 1.0 ) ?name WHERE { ?h rdf:type umbel:HotelBuilding ; } p:location dbpedia:Heraklion ; } rdfs:label ?name . TRUST AS ?t } ORDER BY ?t Returns trustworthy reviews of hotels in Heraklion. Olaf Hartig - Querying Trust in RDF Data with tSPARQL 5
  6. 6. Outline Trust model for RDF data Trust-aware tSPARQL query processing Evaluating trust requirements Query optimization Olaf Hartig - Querying Trust in RDF Data with tSPARQL 6
  7. 7. Trustworthiness of RDF Data ● The trustworthiness of RDF statements is the subjective belief or disbelief in the truth of the statements. ● Represented by trust values in the interval [-1,1] rdfs:label <http://.../data/KnossosRoyal> Aldemar Knossos Royal Village ex: loc rd ate f:t d At t 5.5378 geo:la yp e geo:l umbel:HotelBuilding ong −0.2274 Olaf Hartig - Querying Trust in RDF Data with tSPARQL 7
  8. 8. Atomic Trust ● A trust function associates single RDF statements with a subjective trust value. <http://.../data/KnossosRoyal> TrustFct ( , ) = 0.8 rd f:t yp e umbel:HotelBuilding Trust weighted statement • Trust weighted RDF graph rdfs:label <http://.../data/KnossosRoyal> Aldemar Knossos Royal Village [0.9] ex: [0.1] loc rd ate [0.75] f:t [0.8] dA t 5.5378 t geo:la yp e geo:l umbel:HotelBuilding ong −0.2274 [0.75] Olaf Hartig - Querying Trust in RDF Data with tSPARQL 8
  9. 9. Aggregated Trust ● A trust aggregation function calculates an aggregated trust value for a trust weighted RDF graph. ● Minimum (cautious): tamin = 0.1 ● Median (more optimistic): tamedian = 0.75 rdfs:label <http://.../data/KnossosRoyal> Aldemar Knossos Royal Village [0.9] ex: [0.1] loc rd ate [0.75] f:t [0.8] dA t 5.5378 t geo:la yp e geo:l umbel:HotelBuilding ong −0.2274 [0.75] Olaf Hartig - Querying Trust in RDF Data with tSPARQL 9
  10. 10. Outline Trust model for RDF data Trust-aware tSPARQL query processing Evaluating trust requirements Query optimization Olaf Hartig - Querying Trust in RDF Data with tSPARQL 10
  11. 11. Trust-aware query processing ● SPARQL does not consider trust values ● Basic idea: ● Extend the notion of solutions ● Redefine the algebra operators Olaf Hartig - Querying Trust in RDF Data with tSPARQL 11
  12. 12. Basic graph pattern matching <http://.../data/KnossosRoyal> rev:hasReview <http://revyu.../R457> re v rd :ha rev sR :tex f:t e vie t yp w e What a lovely ... umbel:HotelBuilding <http://revyu.../R337> rev:te xt A surprisingly ... BGP <http://.../data/KnossosRoyal> rev:hasReview ?r rev:text ?t µ Solution mappings ?r ?t that are solutions: http://revyu.../R457 quot;What a lovely ...quot; http://revyu.../R337 quot;A surprisingly ...quot; Olaf Hartig - Querying Trust in RDF Data with tSPARQL 12
  13. 13. Basic graph pattern matching <http://.../data/KnossosRoyal> rev:hasReview <http://revyu.../R457> re v rd :ha rev sR :tex f:t e vie t yp w e What a lovely ... umbel:HotelBuilding <http://revyu.../R337> rev:te xt A surprisingly ... BGP <http://.../data/KnossosRoyal> rev:hasReview ?r rev:text ?t µ Solution mappings ?r ?t that are solutions: http://revyu.../R457 quot;What a lovely ...quot; http://revyu.../R337 quot;A surprisingly ...quot; Olaf Hartig - Querying Trust in RDF Data with tSPARQL 13
  14. 14. Basic graph pattern matching <http://.../data/KnossosRoyal> rev:hasReview <http://revyu.../R457> re v [0.86] rd :ha rev sR [0.86] :tex [0.7] f:t [0.8] evi t yp ew e What a lovely ... umbel:HotelBuilding <http://revyu.../R337> [0.2] rev:te xt A surprisingly ... BGP <http://.../data/KnossosRoyal> rev:hasReview ?r rev:text ?t Trust weighted µ t solution mappings ?r ?t that are solutions: http://revyu.../R457 quot;What a lovely ...quot; http://revyu.../R337 quot;A surprisingly ...quot; Olaf Hartig - Querying Trust in RDF Data with tSPARQL 14
  15. 15. Basic graph pattern matching <http://.../data/KnossosRoyal> rev:hasReview <http://revyu.../R457> re v [0.86] rd :ha rev sR [0.86] :tex [0.7] f:t [0.8] evi t yp ew e What a lovely ... umbel:HotelBuilding <http://revyu.../R337> [0.2] rev:te xt A surprisingly ... BGP <http://.../data/KnossosRoyal> rev:hasReview ?r rev:text ?t Trust weighted µ t solution mappings ?r ?t that are solutions: http://revyu.../R457 quot;What a lovely ...quot; http://revyu.../R337 quot;A surprisingly ...quot; Olaf Hartig - Querying Trust in RDF Data with tSPARQL 15
  16. 16. Basic graph pattern matching <http://.../data/KnossosRoyal> rev:hasReview <http://revyu.../R457> rev [0.86] rd :ha re v s Re[0.86] :tex [0.7] f:t [0.8] v t yp iew e What a lovely ... umbel:HotelBuilding <http://revyu.../R337> [0.2] rev:te xt A surprisingly ... BGP <http://.../data/KnossosRoyal> rev:hasReview ?r rev:text ?t Trust weighted µ t solution mappings ?r ?t that are solutions: http://revyu.../R457 quot;What a lovely ...quot; 0.7 http://revyu.../R337 quot;A surprisingly ...quot; Olaf Hartig - Querying Trust in RDF Data with tSPARQL 16
  17. 17. Basic graph pattern matching <http://.../data/KnossosRoyal> rev:hasReview <http://revyu.../R457> re v [0.86] rd :ha rev sR [0.86] :tex [0.7] f:t [0.8] evi t yp ew e What a lovely ... umbel:HotelBuilding <http://revyu.../R337> [0.2] rev:te xt A surprisingly ... BGP <http://.../data/KnossosRoyal> rev:hasReview ?r rev:text ?t Trust weighted µ t solution mappings ?r ?t that are solutions: http://revyu.../R457 quot;What a lovely ...quot; 0.7 http://revyu.../R337 quot;A surprisingly ...quot; 0.2 Olaf Hartig - Querying Trust in RDF Data with tSPARQL 17
  18. 18. Trust-aware query processing ● SPARQL does not consider trust values Basic idea: √ ● ● Extend the notion of solutions ● Redefine the algebra operators Olaf Hartig - Querying Trust in RDF Data with tSPARQL 18
  19. 19. Redefining the SPARQL algebra { { ?h rdf:type umbel:HotelBuilding ; p:location dbpedia:Heraklion . } { ?h rev:hasReview [ rev:text ?txt1 ] } } Join BGP BGP ?h rdf:type umbel:HotelBuilding . ?h rev:hasReview [ rev:text ?r ] ?h p:location dbpedia:Heraklion . Olaf Hartig - Querying Trust in RDF Data with tSPARQL 19
  20. 20. Redefining the SPARQL algebra µ ?h ?r ex:KnossosRoyal quot;What a lovely …quot; ex:KnossosRoyal quot;A surprisingly …quot; ex:SheratonTenerife quot;Located direct...quot; Join µ µ ?h ?r ?h ex:KnossosRoyal quot;What a lovely …quot; ex:KnossosRoyal ex:KnossosRoyal quot;A surprisingly …quot; ex:SheratonTenerife ex:SheratonTenerife quot;Located direct...quot; BGP BGP ?h rdf:type umbel:HotelBuilding . ?h rev:hasReview [ rev:text ?r ] ?h p:location dbpedia:Heraklion . Olaf Hartig - Querying Trust in RDF Data with tSPARQL 20
  21. 21. Redefining the SPARQL algebra µ t ?h ?r ex:KnossosRoyal quot;What a lovely …quot; ex:KnossosRoyal quot;A surprisingly …quot; ex:SheratonTenerife quot;Located direct...quot; Join µ t µ t ?h ?r ?h ex:KnossosRoyal quot;What a lovely …quot; 0.9 ex:KnossosRoyal 0.7 ex:KnossosRoyal quot;A surprisingly …quot; 0.2 ex:SheratonTenerife 0.1 ex:SheratonTenerife quot;Located direct...quot; 0.8 BGP BGP ?h rdf:type umbel:HotelBuilding . ?h rev:hasReview [ rev:text ?r ] ?h p:location dbpedia:Heraklion . Olaf Hartig - Querying Trust in RDF Data with tSPARQL 21
  22. 22. Redefining the SPARQL algebra ● A trust merge function calculates a merged trust value for two trust weighted solution mappings. µ t ● Minimum: tmmin ?h ?r ex:KnossosRoyal quot;What a lovely …quot; 0.7 ex:KnossosRoyal quot;A surprisingly …quot; 0.2 ex:SheratonTenerife quot;Located direct...quot; 0.1 Join µ t µ t ?h ?r ?h ex:KnossosRoyal quot;What a lovely …quot; 0.9 ex:KnossosRoyal 0.7 ex:KnossosRoyal quot;A surprisingly …quot; 0.2 ex:SheratonTenerife 0.1 ex:SheratonTenerife quot;Located direct...quot; 0.8 BGP BGP ?h rdf:type umbel:HotelBuilding . ?h rev:hasReview [ rev:text ?r ] ?h p:location dbpedia:Heraklion . Olaf Hartig - Querying Trust in RDF Data with tSPARQL 22
  23. 23. Basic idea ● SPARQL does not consider trust values Basic idea: √ ● ● Extend the notion of solutions ● Redefine the algebra operators √ What is the impact of processing trust values on query execution times ? Olaf Hartig - Querying Trust in RDF Data with tSPARQL 23
  24. 24. Evaluation ● tSPARQL query engine (extension of SPARQL engine ARQ) ● Berlin SPARQL Benchmark (BSBM) ● Simulates e-commerce scenario ● Mix of 12 SPARQL queries ● Generates datasets of different sizes (scaling factor) 3 avg. execution time (in sec.) per query mix ARQ SPARQL tSPARQL engine 2,5 engine with 2 precomputed trust values 1,5 1 0,5 0 0 100 (31800) 200 (60424) 300 (92337) 400 (124305) 500 BSBM Scaling Factor (# of triples) Olaf Hartig - Querying Trust in RDF Data with tSPARQL 24
  25. 25. Evaluation ● Simple provenance-based trust function ● Assumes existence of trust assessments for RDF graphs ● Adopts these trust values for all triples in the graph ARQ SPARQL tSPARQL engine tSPARQL engine avg. execution time (in sec.) per query mix engine with + determining precomputed trust values trust values 10 8 6 4 2 0 0 100 (31800) 200 (60424) 300 (92337) 400 (124305) 500 BSBM Scaling Factor (# of triples) Olaf Hartig - Querying Trust in RDF Data with tSPARQL 25
  26. 26. Outline Trust model for RDF data Trust-aware tSPARQL query processing Evaluating trust requirements Query optimization Olaf Hartig - Querying Trust in RDF Data with tSPARQL 26
  27. 27. Evaluating trust requirements ● Goal: ensuring a certain trustworthiness for the solutions of a specific graph pattern SELECT ?hotelName ?reviewText WHERE { ?hotel rdf:type umbel:HotelBuilding ; p:location dbpedia:Heraklion ; rdfs:label ?hotelName . { ?hotel rev:hasReview ?review . ?review rev:text ?reviewText . ENSURE TRUST ( 0.7 , 1.0 ) } } Olaf Hartig - Querying Trust in RDF Data with tSPARQL 27
  28. 28. Evaluating trust requirements ● Goal: ensuring a certain trustworthiness for the solutions of a specific graph pattern µ t ?h ?r ex:KnossosRoyal quot;What a lovely …quot; 0.9 ex:SheratonTenerife quot;Located direct...quot; 0.8 EnTrust 0.5 , 1.0 µ t ?h ?r ex:KnossosRoyal quot;What a lovely …quot; 0.9 ex:KnossosRoyal quot;A surprisingly …quot; 0.2 ex:SheratonTenerife quot;Located direct...quot; 0.8 EnTrust l , u ,  = {  , t  ∣ , t ∈ ∧ lt u } * * Olaf Hartig - Querying Trust in RDF Data with tSPARQL 28
  29. 29. Evaluating trust requirements Join { { ?h rdf:type umbel:HotelBuilding ; p:location dbpedia:Heraklion . } { ?h rev:hasReview [ rev:text ?txt1 ] ENSURE TRUST ( 0.5 , 1.0 ) } } EnTrust 0.5 , 1.0 BGP BGP ?h rdf:type umbel:HotelBuilding . ?h rev:hasReview [ rev:text ?r ] ?h p:location dbpedia:Heraklion . Olaf Hartig - Querying Trust in RDF Data with tSPARQL 29
  30. 30. Evaluating trust requirements Join { { ?h rdf:type umbel:HotelBuilding ; p:location dbpedia:Heraklion . } { ?h rev:hasReview [ rev:text ?txt1 ] ENSURE TRUST ( 0.5 , 1.0 ) } } EnTrust 0.5 , 1.0 µ t µ t ?h ?r ?h ex:KnossosRoyal quot;What a lovely …quot; 0.9 ex:KnossosRoyal 0.7 ex:KnossosRoyal quot;A surprisingly …quot; 0.2 ex:SheratonTenerife 0.1 ex:SheratonTenerife quot;Located direct...quot; 0.8 BGP BGP ?h rdf:type umbel:HotelBuilding . ?h rev:hasReview [ rev:text ?r ] ?h p:location dbpedia:Heraklion . Olaf Hartig - Querying Trust in RDF Data with tSPARQL 30
  31. 31. Evaluating trust requirementsµ t ?h ?r ex:KnossosRoyal quot;What a lovely …quot; 0.7 ex:SheratonTenerife quot;Located direct...quot; 0.8 Join { µ t { ?h rdf:type umbel:HotelBuilding ; ?h ?r p:location dbpedia:Heraklion . } ex:KnossosRoyal { ?h rev:hasReview [ rev:text ?txt1 ] quot;What a lovely …quot; 0.9 ENSURE TRUST ( 0.5 , 1.0 ) }ex:SheratonTenerife quot;Located direct...quot; 0.8 } EnTrust 0.5 , 1.0 µ t µ t ?h ?r ?h ex:KnossosRoyal quot;What a lovely …quot; 0.9 ex:KnossosRoyal 0.7 ex:KnossosRoyal quot;A surprisingly …quot; 0.2 ex:SheratonTenerife 0.1 ex:SheratonTenerife quot;Located direct...quot; 0.8 BGP BGP ?h rdf:type umbel:HotelBuilding . ?h rev:hasReview [ rev:text ?r ] ?h p:location dbpedia:Heraklion . Olaf Hartig - Querying Trust in RDF Data with tSPARQL 31
  32. 32. Evaluating trust requirementsµ t ?h ?r ex:KnossosRoyal quot;What a lovely …quot; 0.7 ex:SheratonTenerife quot;Located direct...quot; 0.8 EnTrust 0.5 , 1.0 { { ?h rdf:type umbel:HotelBuilding ; p:location dbpedia:Heraklion . } { ?h rev:hasReview [ rev:text ?txt1 ] ENSURE TRUST ( 0.5 , 1.0 ) } ENSURE TRUST ( 0.5 , 1.0 ) } Join BGP BGP ?h rdf:type umbel:HotelBuilding . ?h rev:hasReview [ rev:text ?r ] ?h p:location dbpedia:Heraklion . Olaf Hartig - Querying Trust in RDF Data with tSPARQL 32
  33. 33. Evaluating trust requirementsµ t ?h ?r ex:KnossosRoyal quot;What a lovely …quot; 0.7 ex:SheratonTenerife quot;Located direct...quot; 0.8 EnTrust 0.5 , 1.0 { { ?h rdf:type umbel:HotelBuilding ; p:location dbpedia:Heraklion . } { ?h rev:hasReview [ rev:text ?txt1 ] ENSURE TRUST ( 0.5 , 1.0 ) } ENSURE TRUST ( 0.5 , 1.0 ) } Join µ t µ t ?h ?r ?h ex:KnossosRoyal quot;What a lovely …quot; 0.9 ex:KnossosRoyal 0.7 ex:KnossosRoyal quot;A surprisingly …quot; 0.2 ex:SheratonTenerife 0.1 ex:SheratonTenerife quot;Located direct...quot; 0.8 BGP BGP ?h rdf:type umbel:HotelBuilding . ?h rev:hasReview [ rev:text ?r ] ?h p:location dbpedia:Heraklion . Olaf Hartig - Querying Trust in RDF Data with tSPARQL 33
  34. 34. Evaluating trust requirementsµ µ t t ?h ?r ?h ?r ex:KnossosRoyal quot;What a lovely …quot; 0.7 ex:KnossosRoyal quot;What a lovely …quot; 0.7 ex:SheratonTenerife quot;Located direct...quot; 0.8 EnTrust 0.5 , 1.0 { { ?h rdf:type umbel:HotelBuilding ; µ t p:location dbpedia:Heraklion . ?h } ?r { ?h rev:hasReview [ rev:text ?txt1 ] ex:KnossosRoyal quot;What a lovely …quot; 0.7 ENSURE TRUST ( 0.5 , 1.0 ) }ex:KnossosRoyal quot;A surprisingly …quot; 0.2 ENSURE TRUST ( 0.5 , 1.0 ) ex:SheratonTenerife quot;Located direct...quot; 0.1 } Join µ t µ t ?h ?r ?h ex:KnossosRoyal quot;What a lovely …quot; 0.9 ex:KnossosRoyal 0.7 ex:KnossosRoyal quot;A surprisingly …quot; 0.2 ex:SheratonTenerife 0.1 ex:SheratonTenerife quot;Located direct...quot; 0.8 BGP BGP ?h rdf:type umbel:HotelBuilding . ?h rev:hasReview [ rev:text ?r ] ?h p:location dbpedia:Heraklion . Olaf Hartig - Querying Trust in RDF Data with tSPARQL 34
  35. 35. Evaluating trust requirementsµ µ t t ?h ?r ?h ?r ex:KnossosRoyal quot;What a lovely …quot; 0.7 ex:KnossosRoyal quot;What a lovely …quot; 0.7 ex:SheratonTenerife quot;Located direct...quot; 0.8 EnTrust 0.5 , 1.0 ● Position of the µ t ENSURE TRUST ?h ?r clause matters! ex:KnossosRoyal quot;What a lovely …quot; 0.7 ex:KnossosRoyal quot;A surprisingly …quot; 0.2 ex:SheratonTenerife quot;Located direct...quot; 0.1 Join µ t µ t ?h ?r ?h ex:KnossosRoyal quot;What a lovely …quot; 0.7 ex:KnossosRoyal 0.9 ex:KnossosRoyal quot;A surprisingly …quot; 0.2 ex:SheratonTenerife 0.1 ex:SheratonTenerife quot;Located direct...quot; 0.8 BGP BGP ?h rdf:type umbel:HotelBuilding . ?h rev:hasReview [ rev:text ?r ] ?h p:location dbpedia:Heraklion . Olaf Hartig - Querying Trust in RDF Data with tSPARQL 35
  36. 36. Accessing trust values ● Goal: accessing the trust value for the solution of a specific graph pattern SELECT ?hotel ?hotelName WHERE { ?hotel rdf:type umbel:HotelBuilding ; p:location dbpedia:Heraklion ; rdfs:label ?hotelName . TRUST AS ?t } ORDER BY ?t Olaf Hartig - Querying Trust in RDF Data with tSPARQL 36
  37. 37. Accessing trust values ● Goal: accessing the trust value for the solution of a specific graph pattern ● Again: position of the µ t TRUST AS clause ?h ?r ?t matters! ex:KnossosRoyal quot;What a lovely …quot; 0.9 0.9 ex:SheratonTenerife quot;Located direct...quot; 0.8 0.8 PrTrust ?t µ t ?h ?r ex:KnossosRoyal quot;What a lovely …quot; 0.9 ex:SheratonTenerife quot;Located direct...quot; 0.8 PrTrust v , * = {  ' , t  ∣  , t ∈* ∧  '=∪{  v , lt   } } Olaf Hartig - Querying Trust in RDF Data with tSPARQL 37
  38. 38. Outline Trust model for RDF data Trust-aware tSPARQL query processing Evaluating trust requirements Query optimization Olaf Hartig - Querying Trust in RDF Data with tSPARQL 38
  39. 39. Rewrite Rules ● Rewriting algebra expressions to improve query execution ● E.g., for join operators that employ the trust merge function tmmin holds: EnTrust EnTrust l,u l,u Join Equivalence Join EnTrust EnTrust l , 1.0 l , 1.0 Olaf Hartig - Querying Trust in RDF Data with tSPARQL 39
  40. 40. Evaluation ● Equivalent BSBM-based setup with 6 tSPARQL queries 100 avg. exec.time (in sec.) per query mix tSPARQL engine tSPARQL engine 90 without rewriting with rewriting 80 70 60 50 40 30 20 10 0 0 100 (31800) 200 (60424) 300 (92337) 400 (124305) 500 BSBM Scaling Factor (# of triples) Olaf Hartig - Querying Trust in RDF Data with tSPARQL 40
  41. 41. Take-away summary Trust model for RDF data ● Trust model ● Trust function tSPARQL Trust-aware query processing ● Trust aggregation function Evaluating trust requirements ● Trust in SPARQL query processing Query optimization ● Trust weighted solutions ● Trust-aware algebra ● SPARQL extension for trust requirements ● ENSURE TRUST ● TRUST AS ● tSPARQL query engine available: http://trdf.sourceforge.net Olaf Hartig - Querying Trust in RDF Data with tSPARQL 41
  42. 42. These slides have been created by Olaf Hartig http://olafhartig.de This work is licensed under a Creative Commons Attribution-Share Alike 3.0 License (http://creativecommons.org/licenses/by-sa/3.0/) Olaf Hartig - Querying Trust in RDF Data with tSPARQL 42

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