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SPARQL Query Language for RDF

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1 SPARQL Query Language for RDF
충남대학교 컴퓨터공학과 데이터베이스 시스템 연구실 2017년 3월 25일 토요일

2 Contents SPARQL Status SPARQL Overview SPARQL Feature Summary
References Appendix

3 SPARQL Status SPARQL Query Language for RDF SPARQL Protocol for RDF
W3C, Published W3C Working Draft 26 March 2007 SPARQL Protocol for RDF W3C, Published W3C Candidate Recommendation 6 April 2006 SPARQL Query Results XML Format W3C,

4 SPARQL Overview RDF SPARQL Resource Description Framework
Flexible and extensible way to represent information about WWW resources SPARQL SPARQL Protocol And RDF Query Language Query Language + Protocol + XML Results Format Product of the RDF Data Access Working Group A query language for access and query RDF graphs A protocol for issuing queries via HTTP GET, HTTP POST, or SOAP Perfect for mashing up disparate data sources representable as RDF

5 SPARQL Overview It provides facilities to: Feature
Extract information in the form of URIs, blank nodes, plain and typed literals Extract RDF subgraphs Construct new RDF graphs based on information in the queried graphs Feature Matching graph patterns Variables – global scope; indicated by ‘?‘ or ‘$‘ Query terms – based on Turtle syntax Terms delimited by "<>" are relative URI references Data description format - Turtle

6 Listing 1. SPARQL query to find the URL of a contributor's blog
SPARQL Query Example Figure 1. Basic graph structure for a single contributor in bloggers.rdf Find the URL of the blog by the person named Jon Foobar Listing 1. SPARQL query to find the URL of a contributor's blog PREFIX foaf: < SELECT ?url FROM <bloggers.rdf> WHERE { ?contributor foaf:name "Jon Foobar" . ?contributor foaf:weblog ?url . } Result

7 SPARQL Features Graph Patterns RDF Dataset Result Forms Testing Values
Inference Data Virtualization Access Multiple Sources SPARQL Protocol Walkthrough

8 Graph Patterns Set of Triple Patterns
Triple Pattern – similar to an RDF Triple (subject, predicate, object), but any component can be a query variable; literal subjects are allowed Matching a triple pattern to a graph: bindings between variables and RDF Terms ?book dc:title ?title SELECT ?x ?v WHERE { ?x ?x ?v } rdf:type rdf:type rdf:Property x v rdf:type rdf:Property

9 Graph Pattern - Multiple Matches
@prefix foaf: < . _:a foaf:name "Johnny Lee Outlaw" . _:a foaf:mbox . _:b foaf:name "Peter Goodguy" . _:b foaf:mbox . Data PREFIX foaf: < SELECT ?name ?mbox WHERE { ?x foaf:name ?name . ?x foaf:mbox ?mbox } Query Group Graph Pattern (set of graph patterns) also! name mbox "Johnny Lee Outlaw" "Peter Goodguy" Query Result

10 RDF Dataset The RDF data model expresses information as a graph
Many RDF data stores hold a multiple RDF graphs There is one graph which does not have a name, called the background graph, and zero or more named graphs, identified by URI reference # Default graph @prefix dc: < . < dc:publisher "Bob" . < dc:publisher "Alice" . # Named graph: @prefix foaf: < . _:a foaf:name "Bob" . _:a foaf:mbox .

11 Querying the Dataset # Graph: @prefix foaf: < . _:a foaf:name "Alice" . _:a foaf:mbox . _:a foaf:knows _:b . _:b foaf:name "Bob" . _:b foaf:mbox . _:b foaf:age _:b foaf:PersonalProfileDocument < . # Graph: @prefix foaf: < . _:1 foaf:mbox . _:1 foaf:PersonalProfileDocument < _:1 foaf:age 35 .

12 Accessing Graph Labels
PREFIX foaf: < PREFIX data: < SELECT ?src ?age WHERE GRAPH ?src { ( ?x foaf:mbox ) ( ?x foaf:age ?age ) } src age < 32 < 35 PREFIX foaf: < PREFIX data: < SELECT ?age WHERE GRAPH data:bobFoaf { ( ?x foaf:mbox ) ( ?x foaf:age ?age ) } age 35

13 Result Forms SPARQL has a number of query forms for returning results
SELECT Returns all, or a subset of the variables bound in a query pattern match Formats : XML or RDF/XML CONSTRUCT Returns an RDF graph constructed by substituting variables in a set of triple templates DESCRIBE Returns an RDF graph that describes the resources found ASK Returns whether a query pattern matches or not

14 Testing Values Named functions and syntactically constructed operations: Operands: subset of XML Schema DataTypes {xsd:string, xsd:decimal, xsd:double, xsd:dateTime} and types derived from xsd:decimal. Subset of XQuery 1.0 and XPath 2.0 functions and operators Operands: xs:string, xs:double, xs:float, xs:decimal, xs:integer, xs:dateTime Additional operators: sop:RDFterm-equal, sop:bound, sop:isURI, sop:isBlank, sop:isLiteral, sop:str , sop:lang, sop:datatype, sop:logical-or, sop:logical-and Type Promotion : xs:double, xs:float, xs:decimal Each of the numeric types is promoted to any type higher in the above list when used as an argument to function expecting that higher type

15 Inference An RDF graph may be backed by inference
OWL, RDFS, application, rules PREFIX rdf: < SELECT ?type WHERE { ?x rdf:type ?type . } :x rdf:type :C . :C rdfs:subClassOf :D . | type | ===== | :C | | :D |

16 Data Virtualization SPARQL as integrator SPARQL to SQL
Data remains where it is Existing applications untouched Data appears as RDF, query to native form SPARQL to SQL Direct mapping of tables Semi-automatic generation of mapping SquirrelRDF (also does LDAP) Modelled: D2RQ High-quality mapping, manually developed

17 Federated Query Single Point of Access
Inputs: Service Description Information Directory Request Outputs: Unified results Query Broker SPARQL => SPARQL Doc DB Corp LDAP RDF SPARQL Query

18 Access Multiple Sources
“Find the name and addresses of authors of a paper” Query tech reports first, then go to LDAP for more information. SQL database; LDAP server PREFIX dc: < PREFIX ldap: < PREFIX foaf: SELECT ?name ? { ?doc dc:title ?title . FILTER regex(?title, “SPARQL”) . ?doc dc:creator ?reseacher . ?researcher ldap: ? . ?researcher ldap:name ?name }

19 Access Multiple Sources
“Find the reports written by the person with address Go to LDAP first, then the reports database PREFIX dc: < PREFIX ldap: < PREFIX foaf: SELECT ?name { ?doc dc:title ?title . ?doc dc:creator ?reseacher . ?researcher ldap: . }

20 SPARQL as a Protocol A way of communication between parties that run SPARQL queries Defining a way of invoking the service Bindings of a transport protocol

21 SPARQL Protocol(1) WSDL description file: HTTP binding: SOAP binding:
Description of the protocol Not for human understanding HTTP binding: Specify how to encode SPARQL queries in URLs with GET and POST methods SOAP binding: Specify the SOAP message format (XML message exchange format for queries)

22 SPARQL Protocol(2) Interface SparqlQuery
Only one operation: query For transferring string query Data types: via XML schema Bindings: HTTP / SOAP binding for invokable operations A service must support SparqlQuery interface Support the bindings as described in the WSDL

23 HTTP Binding Example HTTP Binding Get methods
GET /sparql/?query=EncodedQuery &default-graph-uri= &named-graph-uri= &named-graph-uri= HTTP/1.1Host: my.example User-agent: sparql-client/0.1

24 WSDL Description File Example
WSDL description file: (HTTP binding part) <binding name="queryHttp" interface="tns:SparqlQuery“ … > <fault name="MalformedQuery" whttp:zode="400"/> <!-- the GET binding for query operation --> <operation ref="tns:query" whttp:method="GET" whttp:inputSerialization=“…" /> </binding>

25 SOAP Binding Example HTTP/1.1 200 OK
Date: Wed, 27 Dec :48:25 GMT Server: Apache/ (Unix) PHP/4.3.4 DAV/1.0.3 Connection: closeContent-Type: application/sparql-results+xml; charset=utf-8 <?xml version="1.0"?> <sparql xmlns=“…"> … … </sparql>

26 Walkthrough Example(1)
XML File <Person> <name>Henry Story</name> <knows> <Person> <name>Tim Bray</name> </Person> <Person> <name>Jonathan Story</name> </Person> </knows> </Person>

27 Walkthrough Example(1)
SPARQL [ a :Person; :name "Henry Story"; :mbox :knows [ a :Person; :name "Tim Bray"; :mbox ]; :knows [ a :Person; :name "Jonathan Story"; :mbox ]; ] .

28 Graph Representation

29 Walkthrough Example(2)
XML File <AddressBook> <Person> <name>Jonathan Story</name> <address> <Country>France</Country> </address> </Person> <Person> <name>Tim Bray</name> <address> <Country>Canada</Country> </AddressBook>

30 Walkthrough Example(2)
SPARQL [ a :Person; :name "Tim Bray"; :mbox :address [ a :Address; :country ] ]. :name "Jonathan Story"; :mbox :country ]

31 Graph Representation

32 Merge Graph Representation

33 Summary SPARQL (SPARQL Protocol And RDF Query Language) is a query language for getting information from RDF graphs It provides facilities to: Extract information in the form of URIs, bNodes, Plain and typed literals Extract RDF subgraphs Construct new RDF graphs based on information in the queried graphs

34 References W3C, “SPARQL Query Language for RDF” 26, March. 2007 IBM Developerworks, “Search RDF data with SPARQL” 10, May. 2005 Oreillynet, “SPARQL: Web 2.0 Meet the Semantic Web” 16, September. 2005

35 Appendix-01 SPARQL Update Future HP proposal to W3C
INSERT { book:newBook dc:title “More about SPARQL” . book:newBook dc:creator [ foaf:mbox ; foaf:name “Alex Author” ] } DELETE { ?book dc:title ?title ; dc:creator ?c } WHERE { ?book dc:title ?title ; dc:creator ?c FILTER regex(?title, “first edition”) }

36 Appendix-02 SPARQL: Web 2.0 Meet the Semantic Web
RDF is pretty foundational to the Semantic Web Most Web 2.0 applications and services involve a REST protocol or interface REST offers a standard set of operations GET, PUT, POST, DELETE No standard way to execute an arbitrary query A Web 2.0 app or service’s dataset Get back a representation of that resource

37 Appendix-02 SW and Web 2.0 need a data access protocol
Using WSDL 2.0, SPARQL Protocol for RDF describes a very simple web service with one operation, query Available with both HTTP and SOAP bindings The way you send SPARQL queries to other sites The way you get back the results Imagine having one query language, and one client, which lets you arbitrarily slice the data of Web 2.0 sites, all FOAF files, all of the RSS 1.0 feeds A good SPARQL client implementation in Javascript, along with some conventions for building and moving queries around in an AJAX-friendly way SPARQL over AJAX just by itself is so cool it gives me a headache!

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