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Enabling Fine-grainedRDF Data Completeness AssessmentFariz Darari, Simon Razniewski, Radityo E. Prasojo, Werner NuttKRDB, Free University of Bozen-Bolzano, ItalyICWE 2016Lugano, SwitzerlandJune 8, 2016Supported by the project MAGIC, funded by the province of BolzanoManaging Completeness over Web Data June 8, 2016 1 / 31

Quality of Web Data: CompletenessHow complete are Web data sources?Managing Completeness over Web Data June 8, 2016 2 / 31

How complete is Wikidata for Apollo 11’s crew?Managing Completeness over Web Data June 8, 2016 3 / 31

NASA says . . .Managing Completeness over Web Data June 8, 2016 4 / 31

Wikidata is complete for Apollo 11’s crew!Managing Completeness over Web Data June 8, 2016 5 / 31

Wikidata supports a special form ofcompleteness statementManaging Completeness over Web Data June 8, 2016 6 / 31

Completeness StatementsSyntax:Compl(s, p, ?o)Managing Completeness over Web Data June 8, 2016 7 / 31

Completeness StatementsSyntax:Compl(s, p, ?o)Semantics:Graph G has Compl(s, p, ?o)Managing Completeness over Web Data June 8, 2016 7 / 31

Completeness StatementsSyntax:Compl(s, p, ?o)Semantics:Graph G has Compl(s, p, ?o)↓G is complete for all p-values of s that exist in realityManaging Completeness over Web Data June 8, 2016 7 / 31

Usages of Completeness StatementsTracking data completion progress of KB contributorsManaging Completeness over Web Data June 8, 2016 8 / 31

Usages of Completeness StatementsTracking data completion progress of KB contributorsProviding statistics about completeness of KBsExample: For 25% of Swiss cantons, Wikidata is completefor their ofﬁcial languages.Managing Completeness over Web Data June 8, 2016 8 / 31

Usages of Completeness StatementsTracking data completion progress of KB contributorsProviding statistics about completeness of KBsExample: For 25% of Swiss cantons, Wikidata is completefor their ofﬁcial languages.Checking query completenessManaging Completeness over Web Data June 8, 2016 8 / 31

Checking Query CompletenessGA99: graph about the space mission A99Managing Completeness over Web Data June 8, 2016 9 / 31

Checking Query CompletenessGA99: graph about the space mission A99P1: query for schools of the children of A99’s crew{ (A99, crew, ?cr), (?cr, child, ?ch), (?ch, school, ?sc) }Managing Completeness over Web Data June 8, 2016 9 / 31

Checking Query CompletenessGA99: graph about the space mission A99P1: query for schools of the children of A99’s crew{ (A99, crew, ?cr), (?cr, child, ?ch), (?ch, school, ?sc) }Evaluating P1 over GA99 gives one answer mapping:{?cr → Chan, ?ch → Dani, ?sc → USI}Managing Completeness over Web Data June 8, 2016 9 / 31

Checking Query CompletenessGA99: graph about the space mission A99P1: query for schools of the children of A99’s crew{ (A99, crew, ?cr), (?cr, child, ?ch), (?ch, school, ?sc) }Evaluating P1 over GA99 gives one answer mapping:{?cr → Chan, ?ch → Dani, ?sc → USI}Is P1 complete over GA99?Managing Completeness over Web Data June 8, 2016 9 / 31

Checking Query CompletenessGA99: graph about the space mission A99P1: query for schools of the children of A99’s crew{ (A99, crew, ?cr), (?cr, child, ?ch), (?ch, school, ?sc) }Evaluating P1 over GA99 gives one answer mapping:{?cr → Chan, ?ch → Dani, ?sc → USI}Is P1 complete over GA99? We don’t know!Managing Completeness over Web Data June 8, 2016 9 / 31

Checking Query CompletenessP1 = { (A99, crew, ?cr), (?cr, child, ?ch), (?ch, school, ?sc) }CA99: set of completeness statements consisting ofC1 = Compl(A99, crew, ?o)Managing Completeness over Web Data June 8, 2016 10 / 31

Checking Query CompletenessP1 = { (A99, crew, ?cr), (?cr, child, ?ch), (?ch, school, ?sc) }CA99: set of completeness statements consisting ofC1 = Compl(A99, crew, ?o)C2 = Compl(Bob, child, ?o)Managing Completeness over Web Data June 8, 2016 11 / 31

Checking Query CompletenessP1 = { (A99, crew, ?cr), (?cr, child, ?ch), (?ch, school, ?sc) }CA99: set of completeness statements consisting ofC1 = Compl(A99, crew, ?o)C2 = Compl(Bob, child, ?o)C3 = Compl(Chan, child, ?o)Managing Completeness over Web Data June 8, 2016 12 / 31

Checking Query CompletenessP1 = { (A99, crew, ?cr), (?cr, child, ?ch), (?ch, school, ?sc) }CA99: set of completeness statements consisting ofC1 = Compl(A99, crew, ?o)C2 = Compl(Bob, child, ?o)C3 = Compl(Chan, child, ?o)C4 = Compl(Dani, school, ?o)Managing Completeness over Web Data June 8, 2016 13 / 31

Checking Query CompletenessP1 = { (A99, crew, ?cr), (?cr, child, ?ch), (?ch, school, ?sc) }CA99: set of completeness statements consisting ofC1 = Compl(A99, crew, ?o)C2 = Compl(Bob, child, ?o)C3 = Compl(Chan, child, ?o)C4 = Compl(Dani, school, ?o)Is P1 complete over GA99 wrt. CA99?Managing Completeness over Web Data June 8, 2016 14 / 31

Checking Query CompletenessP1 = { (A99, crew, ?cr), (?cr, child, ?ch), (?ch, school, ?sc) }C1 matches the ﬁrst triple of P1

Checking Query CompletenessP1 = { (A99, crew, ?cr), (?cr, child, ?ch), (?ch, school, ?sc) }C1 matches the ﬁrst triple of P1 → Complete for Pc1 = (A99, crew, ?cr)

Checking Query CompletenessP1 = { (A99, crew, ?cr), (?cr, child, ?ch), (?ch, school, ?sc) }C1 matches the ﬁrst triple of P1 → Complete for Pc1 = (A99, crew, ?cr)Instantiating the rest of P1 with the answers of Pc1 gives:P2 = { (Bob, child, ?ch), (?ch, school, ?sc) }P3 = { (Chan, child, ?ch), (?ch, school, ?sc) }Managing Completeness over Web Data June 8, 2016 15 / 31

Checking Query CompletenessP2 = { (Bob, child, ?ch), (?ch, school, ?sc) }C2 matches the ﬁrst triple of P2

Checking Query CompletenessP2 = { (Bob, child, ?ch), (?ch, school, ?sc) }C2 matches the ﬁrst triple of P2 → Complete for Pc2 = (Bob, child, ?ch)

Checking Query CompletenessP2 = { (Bob, child, ?ch), (?ch, school, ?sc) }C2 matches the ﬁrst triple of P2 → Complete for Pc2 = (Bob, child, ?ch)Instantiating the rest of P2 with the answers of Pc2 gives: nothingComplete for P2Managing Completeness over Web Data June 8, 2016 16 / 31

Checking Query CompletenessP3 = { (Chan, child, ?ch), (?ch, school, ?sc) }C3 matches the ﬁrst triple of P3

Checking Query CompletenessP3 = { (Chan, child, ?ch), (?ch, school, ?sc) }C3 matches the ﬁrst triple of P3 → Complete forPc3 = (Chan, child, ?ch)

Checking Query CompletenessP3 = { (Chan, child, ?ch), (?ch, school, ?sc) }C3 matches the ﬁrst triple of P3 → Complete forPc3 = (Chan, child, ?ch)Instantiating the rest of P3 with the answers of Pc3 gives:P4 = { (Dani, school, ?sc) }Managing Completeness over Web Data June 8, 2016 17 / 31

Checking Query CompletenessP4 = { (Dani, school, ?sc) }C4 matches the only triple of P4

Checking Query CompletenessP4 = { (Dani, school, ?sc) }C4 matches the only triple of P4 → Complete for the whole P4Managing Completeness over Web Data June 8, 2016 18 / 31

Checking Query CompletenessP4 = { (Dani, school, ?sc) }C4 matches the only triple of P4 → Complete for the whole P4Conclusion: We found complete matchesfor all query instantiations from P1Managing Completeness over Web Data June 8, 2016 18 / 31

Checking Query CompletenessP4 = { (Dani, school, ?sc) }C4 matches the only triple of P4 → Complete for the whole P4Conclusion: We found complete matchesfor all query instantiations from P1→ P1 is complete over GA99 wrt. CA99Managing Completeness over Web Data June 8, 2016 18 / 31

Algorithm for Checking Query CompletenessInput: P query, G graph, C set of completeness statementsOutput: true iff P is complete wrt. G and CP ← {P}while P = ∅ dochoose and remove P0 ∈ PPc0 ← FindMatch(P0, C)if Pc0 = ∅return falseelsePrest0 ← P0 Pc0P ← P ∪ {µPrest0 | µ ∈ Pc0 G}return trueManaging Completeness over Web Data June 8, 2016 19 / 31

Experimental QuestionsWhat is the relationship between the number of query answersand completeness checking time?How do query evaluation time and completeness checkingtime compare?Is there a difference between completeness checking timefor complete and incomplete cases?Managing Completeness over Web Data June 8, 2016 20 / 31

Experimental SetupGraph: WikidataManaging Completeness over Web Data June 8, 2016 21 / 31

Experimental SetupGraph: WikidataQueries: Three sets of path queries with an increasing number ofquery results (3 sets x 40 queries)Pmot = { ($c$, mother, ?w), (?w, mother, ?x), (?x, mother, ?y) }Pcre = { ($c$, crew, ?w), (?w, mission, ?x), (?x, operator, ?y) }Pdiv = { ($c$, division, ?w), (?w, division, ?x), (?x, area, ?y) }Managing Completeness over Web Data June 8, 2016 21 / 31

Experimental SetupGraph: WikidataQueries: Three sets of path queries with an increasing number ofquery results (3 sets x 40 queries)Pmot = { ($c$, mother, ?w), (?w, mother, ?x), (?x, mother, ?y) }Pcre = { ($c$, crew, ?w), (?w, mission, ?x), (?x, operator, ?y) }Pdiv = { ($c$, division, ?w), (?w, division, ?x), (?x, area, ?y) }Completeness statements:Complete case: generated by traversing the query structure(1.7 mio statements)Incomplete case: drop randomly 20% of the statementsin the complete caseManaging Completeness over Web Data June 8, 2016 21 / 31

Experimental SetupImplementation: Java with the Apache Jena libraryCompleteness statement matching = standard Java HashMapTriple store = Jena-TDBMachine: 2.4 GHz laptop with 8 GB memoryManaging Completeness over Web Data June 8, 2016 22 / 31

Experimental ResultsThe more the query results, the longer the completeness checksManaging Completeness over Web Data June 8, 2016 23 / 31

Experimental ResultsThe more the query results, the longer the completeness checksThough slower than query evaluation, in an absolute scalecompleteness checking performs reasonably well (at most 35 ms)Managing Completeness over Web Data June 8, 2016 23 / 31

Experimental ResultsThe more the query results, the longer the completeness checksThough slower than query evaluation, in an absolute scalecompleteness checking performs reasonably well (at most 35 ms)Complete cases are slower than incomplete casesManaging Completeness over Web Data June 8, 2016 23 / 31

Practical Applications of Completeness StatementsHow complete are Web data sources?To answer the question, we need to provideA way to annotate complete parts of a data source usingcompleteness statementsWays to utilize the completeness statements to give insightson how complete the data source isManaging Completeness over Web Data June 8, 2016 24 / 31

COOL-WD: COmpleteness toOL for WikiDataWe have developeda demo of completeness management tool for WikidataCOOL-WD provides ways toannotate complete parts of Wikidatautilize completeness statements to do completenessaggregation and query completeness assessmentManaging Completeness over Web Data June 8, 2016 25 / 31

COOL-WD: Detailed FeaturesManagement of completeness statementsAdding or removing completeness statements of any property of aWikidata entityViewing an entity page with its completeness annotationsAggregation of completeness statementsAssessment of query completenessManaging Completeness over Web Data June 8, 2016 26 / 31

COOL-WD: ArchitectureSPARQLEndpoint MediaWiki APICOOL-WDEngineCOOL-WDUserInterfaceHTTP RequestsData Access Web BrowsingSPARQL Queries API CallsCompleteness DBManaging Completeness over Web Data June 8, 2016 27 / 31

COOL-WD: Demohttp://cool-wd.inf.unibz.it/Managing Completeness over Web Data June 8, 2016 28 / 31

ConclusionsWe developed a sound and complete algorithmfor query completeness checking wrt. an RDF graph andcompleteness statementsManaging Completeness over Web Data June 8, 2016 29 / 31

ConclusionsWe developed a sound and complete algorithmfor query completeness checking wrt. an RDF graph andcompleteness statementsThe algorithm can be generalized to consider a more general formof completeness statements: Compl(P) where P is a basic graphpattern (BGP)Managing Completeness over Web Data June 8, 2016 29 / 31

ConclusionsWe developed a sound and complete algorithmfor query completeness checking wrt. an RDF graph andcompleteness statementsThe algorithm can be generalized to consider a more general formof completeness statements: Compl(P) where P is a basic graphpattern (BGP)We evaluated completeness checking performanceManaging Completeness over Web Data June 8, 2016 29 / 31

ConclusionsWe developed a sound and complete algorithmfor query completeness checking wrt. an RDF graph andcompleteness statementsThe algorithm can be generalized to consider a more general formof completeness statements: Compl(P) where P is a basic graphpattern (BGP)We evaluated completeness checking performanceWe developed COOL-WD, a completeness tool for WikidataManaging Completeness over Web Data June 8, 2016 29 / 31

Ongoing WorkWe plan to leverage completeness statements for checkingthe soundness of queries with negation1We plan to develop fast completeness checks for arbitrarycompleteness statements11Darari et al. Ensuring Soundness for SPARQL with Negation UsingCompleteness Statements. Submitted to a conference.Managing Completeness over Web Data June 8, 2016 30 / 31

Ongoing WorkWe plan to leverage completeness statements for checkingthe soundness of queries with negation1We plan to develop fast completeness checks for arbitrarycompleteness statements1We plan to exploit the potential of natural language completenessstatements already available on the Web: 14K in Wikipedia,24K in IMDb, 2200 in OpenStreetMap1Darari et al. Ensuring Soundness for SPARQL with Negation UsingCompleteness Statements. Submitted to a conference.Managing Completeness over Web Data June 8, 2016 30 / 31

Ongoing WorkWe plan to leverage completeness statements for checkingthe soundness of queries with negation1We plan to develop fast completeness checks for arbitrarycompleteness statements1We plan to exploit the potential of natural language completenessstatements already available on the Web: 14K in Wikipedia,24K in IMDb, 2200 in OpenStreetMapWe plan to extend COOL-WD with new cool featuresCompleteness analyticsQuery completeness diagnosticsLinked data publication of completeness statementsCompleteness gadget for tighter integration with Wikidata1Darari et al. Ensuring Soundness for SPARQL with Negation UsingCompleteness Statements. Submitted to a conference.Managing Completeness over Web Data June 8, 2016 30 / 31

Thank you!Questions? Just drop Fariz an email: fadirra@gmail.comBig thanks to Springer for the travel grant!Have a look at the paper:http://dx.doi.org/10.1007/978-3-319-38791-8_10And ﬁnally, a completeness statement for all the slides :-)Compl(thisSlideset, hasSlide, ?o)Managing Completeness over Web Data June 8, 2016 31 / 31

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