05/01/2016 SPARQL SPARQL Protocol and RDF Query Language S. Garlatti

Computer Science DepartmentSemantic Web in Actionpage 1 Outline SPARQL

Computer Science DepartmentSemantic Web in Actionpage 2 SPARQL: SPARQL Protocol and RDF Query Language SPARQL pronounced "sparkle" [1]) is an RDF query language; its name is a recursive acronym that stands for SPARQL Protocol and RDF Query Language. It is standardized by the RDF Data Access Working Group (DAWG) of the World Wide Web Consortium, and is considered a component of the semantic web.sparkle[1]RDF query languagerecursive acronymWorld Wide Web Consortiumsemantic web Initially released as a Candidate Recommendation in April 2006, but returned to Working Draft status in October 2006, due to two open issues. [2] In June 2007, SPARQL advanced to Candidate Recommendation once again. [3] On 12th November 2007 the status of SPARQL changed into Proposed Recommendation. [4] On 15th January 2008, SPARQL became an official W3C Recommendation. [5][2][3][4][5]

Computer Science Department SPARQL: SPARQL Protocol and RDF Query Language SPARQL = A Query Language A Result Form An Access Protocol Linked Data & Social Webpage 3

Computer Science Department SPARQL: SPARQL Protocol and RDF Query Language The Query Language: query forms « Select » clause returns all or subset of the variables bound in a query pattern match « Construct » returns an RDF graph constructed by substituting variables in a set of triple templates « Ask » returns a boolean indicating whether a query pattern matches « Describe » returns an RDF graph that describe the resources found Linked Data & Social Webpage 4

Computer Science Department SPARQL: SPARQL Protocol and RDF Query Language « Select » equivalent to « SQL Select » returns a regular table Select … From … Identify data sources to query Where { … } The triple/graph pattern to be matched against the triple/graphs of RDF A conjunction of triples PREFIX to declare the schema used in the query Linked Data & Social Webpage 5

Computer Science Department SPARQL: SPARQL Protocol and RDF Query Language PREFIX foaf: SELECT ?name FROM WHERE { ?x foaf:name ?name } Result: Linked Data & Social Webpage 6 name « Alice »

Computer Science DepartmentSemantic Web in Actionpage 7 SPARQL: SPARQL Protocol and RDF Query Language PREFIX foaf: PREFIX : PREFIX dbpedia2: PREFIX dbpedia: SELECT distinct ?name ?birth ?person FROM WHERE { ?person dbpedia2:birthPlace. ?person dbpedia2:birth ?birth. ?person foaf:name ?name. }

Computer Science DepartmentSemantic Web in Actionpage 8 SPARQL: SPARQL Protocol and RDF Query Language SPARQL results: namebirthperson« ":Dru_Berrymore/birth/birth_date_and_age :Dru_Berrymore "Dru :Dru_Berrymore "Walter :Walter_Benjamin "Walter :Walter_Benjamin:Dru_Berrymore/birth/birth_date_and_age :Dru_Berrymore:Dru_Berrymore/birth/birth_date_and_age :Dru_Berrymore:Berlin :Walter_Benjamin :Germany :Walter_Benjamin NameBirthPerson « Dru Berrymore »

Computer Science DepartmentSemantic Web in Actionpage 9 SPARQL: SPARQL Protocol and RDF Query Language SELECT distinct ?name ?person FROM WHERE { ?person dbpedia2:birthPlace. ?person foaf:name ?name. } SELECT distinct ?name ?birth ?death ?person FROM WHERE { ?person dbpedia2:birthPlace. ?person dbpedia2:birth ?birth. ?person foaf:name ?name. ?person dbpedia2:death ?death. }

Computer Science Department SPARQL: SPARQL Protocol and RDF Query Language A constraint, expressed by the keyword “FILTER”, is a restriction on solutions over the whole group in which the filter appears PREFIX dc: PREFIX ns: SELECT ?title ?price WHERE { ?x ns:price ?price. FILTER (?price < 30.5) ?x dc:title ?title. } Linked Data & Social Webpage 10

Computer Science Department SPARQL: SPARQL Protocol and RDF Query Language “regex” matches only plain literals with no language tag { ?x foaf:name ?name. ?x foaf:mbox ?mbox. FILTER regex(?name, "Smith") } PREFIX dc: SELECT ?title WHERE { ?x dc:title ?title FILTER regex(?title, "web", "i" ) } Linked Data & Social Webpage 11

Computer Science Department SPARQL: SPARQL Protocol and RDF Query Language Optional parts of the graph pattern may be specified syntactically with the “OPTIONAL” keyword applied to a graph pattern SELECT distinct ?name ?birth ?death ?person FROM WHERE { ?person dbpedia2:birthPlace. ?person dbpedia2:birth ?birth. ?person foaf:name ?name. OPTIONAL {?person dbpedia2:death ?death} } Linked Data & Social Webpage 12

Computer Science Department SPARQL: SPARQL Protocol and RDF Query Language Matching alternative Pattern alternatives are syntactically specified with the UNION keyword SELECT distinct ?name ?birth ?death ?person WHERE { {?person dbpedia2:birthPlace } UNION {?person dbpedia2:death ?death} ?person foaf:name ?name. ?person dbpedia2:birth ?birth. } Linked Data & Social Webpage 13

Computer Science Department SPARQL: SPARQL Protocol and RDF Query Language Sequence & Modify « Order By » to sort, « LIMIT » result number, « OFFSET » rank of first result SELECT distinct ?name ?person WHERE { ?person dbpedia2:birthPlace. ?person foaf:name ?name. } ORDER BY ?name LIMIT 20 OFFSET 20 Linked Data & Social Webpage 14

Computer Science Department SPARQL: SPARQL Protocol and RDF Query Language « Construct » The CONSTRUCT query form returns a single RDF graph specified by a graph template. -The result is an RDF graph formed by taking each query solution in the solution sequence, substituting for the variables in the graph template, and combining the triples into a single RDF graph by set union. Useful for aggregating data from multiple sources and merging it into a local store (from Ingenta) Linked Data & Social Webpage 15

Computer Science Department SPARQL: SPARQL Protocol and RDF Query Language PREFIX foaf: FROM ; foaf:knows ?friend. ?friend foaf:name ?name; foaf:homepage ?home.} Linked Data & Social Webpage 16

Computer Science Department SPARQL: SPARQL Protocol and RDF Query Language ASK Returns a true/false value: test whether or not a query pattern has a solution. No information is returned about the possible query solutions, just whether or not a solution exists Is there data that looks like this? Do you have any information about that? (from Ingenta) PREFIX foaf: ASK WHERE { ?person a foaf:Person; foaf:mbox. } Semantic Web in Actionpage 17

Computer Science Department SPARQL: SPARQL Protocol and RDF Query Language DESCRIBE The DESCRIBE form returns a single result RDF graph containing RDF data about resources. CONSTRUCT but with less control -Tell me about this or things that look like this … but you decide what’s relevant (from Ingenta) PREFIX foaf: DESCRIBE ?friend WHERE { ?person foaf:mbox foaf:knows ?friend.} Semantic Web in Actionpage 18

Computer Science Department SPARQL: SPARQL Protocol and RDF Query Language Applied uses (from Ingenta) DESCRIBE for Prototyping - DESCRIBE -Quickly assembling Uis, Web APIs SELECT for Indexing -Building an ordering over some data ORDER BY, LIMIT Semantic Web in Actionpage 19

Computer Science Department SPARQL: SPARQL Protocol and RDF Query Language Applied uses (from Ingenta) CONSTRUCT for transformation and also simple inferencing -CONSTRUCT could be the XSLT of RDF -Currently limited by lack of expressions in CONSTRUCT triple templates ASK for validation ASK – DESCRIBE – CONSTRUCT Pattern: -Probe endpoint, Grab default view of data, Refine data extraction and/or apply transformation Semantic Web in Actionpage 20

Computer Science Department SPARQL: SPARQL Protocol and RDF Query Language SPARQL Protocol (from F. Gandon, INRIA) Sending queries and their results accross the web Example with HTTP binding GET /sparql/?query= HTTP/1.1 Host: User-agent: my-sparql-client/0.1 Semantic Web in Actionpage 21

Computer Science Department SPARQL: SPARQL Protocol and RDF Query Language Example with SOAP binding (from F. Gandon) SELECT ?x ?p ?y WHERE {?x ?p ?y} Semantic Web in Actionpage 22

Computer Science Department SPARQL: SPARQL Protocol and RDF Query Language Access to Data on the web Etc. Twinkle : a sparql query tool Linked Data & Social Webpage 23

Computer Science DepartmentSemantic Web in Actionpage 24 SPARQL: SPARQL Protocol and RDF Query Language Resources