Alexandra Cristea 1

 pronounced "sparkle“  recursive acronym for: ◦ SPARQL Protocol and RDF Query Language  a semantic query language  a query language for RDF(S)  W3C Recommendation 15 th January 2008 ◦ provides a standard format for writing queries that target RDF data ◦ and a set of standard rules for processing queries and returning the results  2

 New version: 21 st of March 2013:   Query language at:   Implemented in various programming languages 3

4 Subject Predicate author Object Jan Egil Refsnes SPARQL searches for all sub-graphs that match the graph described by the triples in the query. ?subject ?predicate ?object

SELECT ?student WHERE { ?student b:studies bmod:CS414 } ~ SQL – why? Which are the namespace prefixes? 5

In RDF: In SPARQL: PREFIX b: PREFIX bmod: <  The PREFIX keyword is SPARQL ’ s version of an xmlns:namespace declaration and works in basically the same way. 6

PrefixIRI rdf: rdfs: xsd: fn: sfn: 7 Prefixes are not optional in SPARQL!

 Capitals of Europe: 8

    9

    - Fluidops     

 OpenLink Query point ◦  Semanticweb.org data: ◦  Diseases: ◦  Country statistics: ◦  Nobelprize info: ◦  W3C’s list of endpoints: ◦

   ◦ make sure to allow at ‘Sponging’ to ‘Retrieve remote RDF data for all missing source graphs’ 

 Different syntax from XML  Variables: begin with ? or $  triples patterns enclosed within braces {}  Result: variables after SELECT (~SQL) 13

 PREFIX foo:  PREFIX bar:  SELECT …  FROM …  WHERE {…}  GROUP BY …  HAVING …  ORDER BY …  LIMIT …  OFFSET …  VALUES … 14 ~ SQL

 SELECT queries  CONSTRUCT queries  ASK queries  DESCRIBE queries 15

PREFIX foaf: SELECT ?x ?y ?z FROM WHERE { ?x ?y ?z } 16

PREFIX b: PREFIX bmod: PREFIX foaf: SELECT ?name WHERE { ?student b:studies bmod:CS328. ?student foaf:name ?name } 17

 FOAF (Friend Of A Friend)  experimental project using RDF, defining a standardised vocabulary.  Goal: make personal homepages machine- readable & understandable, create an internet- wide connected database of people. Defined at: 18

 Idea: most personal homepages contain similar info. ◦ E.g, person’s name, living place, work place, details on work of the moment, links to friends. ◦ define RDF predicates to represent them. ◦ So: Pages: understood/ manipulated by computers.  So a db can be queried for: ◦ “ what projects are my friends working on? ”, ◦ “ do any of my friends know the director of BigCorp? ” etc.. 19

Alexandra I. Cristea <foaf:mbox rdf:resource=" mailto: "/> 20

<rdf:RDF xmlns:rdf=" xmlns:rdfs=" xmlns:foaf=" Peter Brusilovsky Peter Brusilovsky 1fa1a097b3fae4594fa0ec18e2e3da11ac7e0349 Alexandra I. Cristea dba246a0d9ec4a f9a035a7a608ff227f8 sha1sum dba246a0d9ec4a f9a035a7a608ff227f8 21

PREFIX b: PREFIX bmod: PREFIX foaf: SELECT ?module ?name WHERE { ?student b:studies ?module. ?student foaf:name ?name } 22

PREFIX b: PREFIX bmod: terial/ PREFIX foaf: < SELECT ?module ?name WHERE { ?student b:studies ?module ; foaf:name ?name } 23

SELECT ?module ?name WHERE { ?student b:studies ?module. ?student b:studies bmod:CS328 ; foaf:name ?name } is identical to: SELECT ?module ?name WHERE { ?student b:studies ?module, bmod:CS328 ; foaf:name ?name } 24

SELECT ?student ? WHERE { ?student b:studies mod:CS328. ?student foaf:mbox ? }  PB: if a student does not have an address registered, with a foaf:mbox predicate, then the query will not match !! 25

SELECT ?student ? WHERE { ?student b:studies mod:CS328. OPTIONAL { ?student foaf:mbox ? } }  OPTIONAL: match it if it can, but otherwise not reject the overall pattern. 26

 SPARQL basics  SPARQL endpoints: dbpedia, foaf, others  SPARQL type of queries: ◦ SELECT; CONSTRUCT; ASK; DESCRIBE  SQL-like constructs: ◦ SELECT; FROM; WHERE; GROUP BY; HAVING; ORDER BY; LIMIT; OFFSET; VALUES  Some specific constructs: ◦ PREFIX not optional; FROM not always used; OPTIONAL ◦ We are going to look at more specific constructs 27

 Try out at: PREFIX books: PREFIX dc: SELECT $book WHERE {$book title $title }  >> this gives an empty answer/ error.  Versus: PREFIX books: PREFIX dc: SELECT $book WHERE {$book dc:title $title } 28

 try out at : With or without optional PREFIX books: PREFIX dc: SELECT ?book ?author ?title ?date WHERE { ?book dc:creator ?author. ?book dc:title ?title. ?book dc:date ?date } PREFIX books: PREFIX dc: SELECT ?book ?author ?title ?date WHERE { ?book dc:creator ?author. ?book dc:title ?title. OPTIONAL { ?book dc:date ?date } } 29

 Try analysing RDF documents  e.g.:  (on or Protégé, or specific endpoints)  Using SPARQL to find Concepts  endpoints Dbpedia SNORQL query explorer ( the BBC Backstage SPARQL Editor ( or GeoSparql ( to analyse content.Dbpedia SNORQL query explorerBBC Backstage SPARQL EditorGeoSparql  Listing DISTINCT RDF Types  The following query lists the distinct rdf:types used in a dataset  PREFIX rdf: SELECT DISTINCT ?type WHERE { ?s rdf:type ?type }  Listing OWL Classes PREFIX owl: SELECT ?class WHERE { ?class a owl:Class } 30

SELECT ?module ?name ?phone WHERE { ?student b:studies ?module. ?student foaf:name ?name. OPTIONAL { ?student b:contactpermission true. ?student b:phone ?phone } SELECT ?module ?name ?age WHERE { ?student b:studies ?module. ?student foaf:name ?name. OPTIONAL { ?student b:age ?age. FILTER (?age > 25) } } 31

SELECT ?student ? ?home WHERE { ?student b:studies mod:CS328. OPTIONAL { ?student foaf:mbox ? . ?student foaf:homepage ?home } } SELECT ?student ? ?home WHERE { ?student b:studies mod:CS328. OPTIONAL { ?student foaf:mbox ? }. OPTIONAL { ?student foaf:homepage ?home } } 32

SELECT ?student WHERE { ?student foaf:mbox ? . { ?student b:studies mod:CS328 } UNION { ?student b:studies mod:CS909 } }  When patterns are combined using the UNION keyword, the resulting combined pattern will match if any of the subpatterns is matched. 33

 Consider A and B as graph patterns.  { A } UNION { B } ◦ Either / or graph patterns ◦ Disjunction; include both the results of solving A and the results of solving B  { A } MINUS { B } ◦ “subtracted” graph patterns (SPARQL 1.1) ◦ Negation; Solve A; Solve B; Include only those results from A that are not compatible with any of the results from B. 34

 All the previous queries: single RDF graphs.  Often: multiple RDF graphs.  RDF graphs: identified by IRI. ◦ Note: IRI that represents the graph does not have to be the actual IRI of the graph file ◦ although the program processing the query will need to somehow relate the IRI to an actual RDF graph stored somewhere. 35

SELECT ?student ? ?home FROM WHERE { ?student b:studies mod:CS414. OPTIONAL { ?student foaf:mbox ? . ?student foaf:homepage ?home } } By using several FROM declarations, you can combine several graphs in the dataset: SELECT ?student ? ?home FROM WHERE { ?student b:studies mod:CS414. OPTIONAL { ?student foaf:mbox ? . ?student foaf:homepage ?home } } 36

 one (optional) default graph  + any number of named graphs.  FROM specifies default graph. ◦ Many FROM keywords, the graphs are merged into the default graph.  Additionally: named graphs, w FROM NAMED. ◦ However, to match patterns you must use GRAPH keyword to state which graph ! 37

SELECT ?student ? ?home FROM NAMED FROM NAMED WHERE { GRAPH { ?student b:studies mod:CS909 }. GRAPH { OPTIONAL { ?student foaf:mbox ? . ?student foaf:homepage ?home } } 38

PREFIX brdf: SELECT ?student ? ?home FROM NAMED FROM NAMED WHERE { GRAPH brdf:student { ?student b:studies mod:CS909 }. GRAPH brdf:foaf{ OPTIONAL { ?student foaf:mbox ? . ?student foaf:homepage ?home } } 39

PREFIX brdf: SELECT ?student ? ?home FROM FROM NAMED WHERE { ?student b:studies mod:CS909. GRAPH brdf:foaf{ OPTIONAL { ?studentfoaf:mbox? . ?studentfoaf:homepage ?home } } 40

 the GRAPH can also be a variable. ◦ to query which graph in the dataset holds a particular relationship, ◦ or which graph to search based on data in another graph.  not mandatory to declare all graphs ◦ even if specified, the dataset can be overridden on a per-query basis. 41

PREFIX brdf: SELECT ?student ?graph WHERE { ?student b:studies mod:CS909. GRAPH ?graph { ?student foaf:mbox ? }  output var graph holds graph URL (matching student to address).  Presumption: query processor has knowledge of a finite set of graphs + their locations 42

PREFIX brdf: SELECT ?student ? WHERE { ?student b:studies mod:CS909. ?student rdfs:seeAlso ?graph. GRAPH ?graph { ?student foaf:mbox ? }  Note: if student doesn’t have a rdfs:seeAlso property which points to a graph holding their address, they will not appear in the result at all. 43

 Specific SPARQL constructs: ◦ Revisited OPTIONAL, PREFIX, FROM - single ◦ New ones: FILTER, UNION, MINUS, FROM –multiple, FROM NAMED, GRAPH, GRAPH with prefix, GRAPH as (query-able + reusable) variable  More online/ offline queries: ◦ Endpoints ◦ Sparql.com ◦ Protégé  Next: other SQL-like constructs; non-SQL-like behaviour: ASK, DESCRIBE, CONSTRUCT 44

SELECT ?name ?module WHERE { ?student b:studies ?module. ?student foaf:name ?name } ORDER BY ?name SELECT ?name ?age WHERE { ?student b:age ?age. ?student foaf:name ?name } ORDER BY DESC (?age) ASC (?name) 45

SELECT ?name ?module WHERE { ?student b:studies ?module. ?student foaf:name ?name } LIMIT 20 46

SELECT ?name ?module WHERE { ?student b:studies ?module. ?student foaf:name ?name } ORDER BY ?name OFFSET 10 LIMIT 20 47

SELECT ?student WHERE { ?student b:studies ?module } versus: SELECT DISTINCT ?student WHERE { ?student b:studies ?module } 48

 Is any student studying any module? ASK { ?student b:studies ?module }  Is any student studying CS909? ASK { ?student b:studies bmod:CS909 }  Is student studying CS909? ASK { bstu: b:studies bmod:CS909 }  Is anyone whom knows, studying CS909? ASK {bstu: foaf:knows ?x. ?x b:studies bmod: CS909 }  Is any student aged over 30 studying CS909? ASK { ?student b:studies bmod:CS909. ?student b:age ?age. FILTER { ?age > 30 } } 49

CONSTRUCT { ?student b:studyFriend ?friend } WHERE { ?student b:studies ?module. ?student foaf:knows ?friend. ?friend b:studies ?module } }  If there is more than one search result, the triples from each result are combined. 50

 DESCRIBE ?country  Result is in RDF triples, in any RDF serialization 51

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 [1] Dean Allemang & Jim Hendler Semantic Web for the working ontologist. Morgan Kaufmann publishers. ISBN  [2] Eric Prud'hommeaux ; & Andy Seaborne SPARQL Query Language for RDF, [Online]

 Download Jena from  Prot é g é 3.4 and above  Fuseki: x.html x.html 56

 SPARQL language is used for querying RDF.  SPARQL is not based on XML, but on SQL- like syntax.  Building blocks of SPARQL queries are graph patterns that include variables. The result of the query will be the values the vars must take to match the RDF graph.  A SPARQL query can return results in several different ways, as determined by the query.  SPARQL queries can also be used for OWL querying. 57

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