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SPARQL SPARQL SPARQL

admin 11月 11, 2020 0

SPARQL

RDF GRAPH

  • XML/RDF

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    <rdf:RDF                                                                                                                                                                             
      xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'
      xmlns:vCard='http://www.w3.org/2001/vcard-rdf/3.0#'
      xmlns:info='http://somewhere/peopleInfo#'
       >   

      <rdf:Description rdf:about="http://somewhere/JohnSmith/">
        <vCard:FN>John Smith</vCard:FN>
        <info:age rdf:datatype='http://www.w3.org/2001/XMLSchema#integer'>25</info:age>
        <vCard:N rdf:parseType="Resource">
        <vCard:Family>Smith</vCard:Family>
        <vCard:Given>John</vCard:Given>
        </vCard:N>
      </rdf:Description>
    </rdf:RDF>

  • TRUTLE

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    @prefix vCard:   <http://www.w3.org/2001/vcard-rdf/3.0#> .
    @prefix rdf:     <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
    @prefix :        <#> .

    <http://somewhere/MattJones/>
        vCard:FN    "Matt Jones" ;
        vCard:N     [ vCard:Family
                                  "Jones" ;
                      vCard:Given
                                  "Matthew"
                    ] .

  • N3

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    like representation of turtle.

SPARQL QUERY

GRAPH PATTERNS

  • Basic Graph Patterns : where a set of triple patterns must match
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    #dataset
    <rdf:RDF                                                                                                                                                                                                            
      xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'
      xmlns:vCard='http://www.w3.org/2001/vcard-rdf/3.0#'
       >   

      <rdf:Description rdf:about="http://somewhere/JohnSmith/">
        <vCard:FN>John Smith</vCard:FN>
        <vCard:N rdf:parseType="Resource">
        <vCard:Family>Smith</vCard:Family>
        <vCard:Given>John</vCard:Given>
        </vCard:N>
      </rdf:Description>

      <rdf:Description rdf:about="http://somewhere/RebeccaSmith/">
        <vCard:FN>Becky Smith</vCard:FN>
        <vCard:N rdf:parseType="Resource">
        <vCard:Family>Smith</vCard:Family>
        <vCard:Given>Rebecca</vCard:Given>
        </vCard:N>
      </rdf:Description>

      <rdf:Description rdf:about="http://somewhere/SarahJones/">
        <vCard:FN>Sarah Jones</vCard:FN>
        <vCard:N rdf:parseType="Resource">
        <vCard:Family>Jones</vCard:Family>
        <vCard:Given>Sarah</vCard:Given>
        </vCard:N>
      </rdf:Description>

      <rdf:Description rdf:about="http://somewhere/MattJones/">
        <vCard:FN>Matt Jones</vCard:FN>
        <vCard:N
        vCard:Family="Jones"
        vCard:Given="Matthew"/>
      </rdf:Description>

    </rdf:RDF>
    		 
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# basic graph pattern
SELECT ?givenName
WHERE { 
    ?y  <http://www.w3.org/2001/vcard-rdf/3.0#Family>  "Smith" .
    ?y  <http://www.w3.org/2001/vcard-rdf/3.0#Given>  ?givenName .
}
    # same as 
PREFIX vcard: <http://www.w3.org/2001/vcard-rdf/3.0#>
SELECT ?givenName
WHERE { 
    ?y  vcard:Family  "Smith";
        vcard:Given  ?givenName .
}

# result
-------------
| givenName |
=============
| "John"    |
| "Rebecca" |
-------------
 
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# blank node
PREFIX vcard:      <http://www.w3.org/2001/vcard-rdf/3.0#>

SELECT ?y ?givenName
WHERE
 { ?y vcard:Family "Smith" .
   ?y vcard:Given  ?givenName .
 }
 # result
 --------------------
| y    | givenName |
====================
| _:b0 | "John"    |
| _:b1 | "Rebecca" |
--------------------

# note that: Syntax for Blank Nodes
[ :p "v" ] .  ||  _:a0 :p "v" .  # blank node 
[] :p "v" .   # as subject 
:s :q [ :p "v" ] . # as object
 
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# FILTER
PREFIX vcard: <http://www.w3.org/2001/vcard-rdf/3.0#>

SELECT ?g
WHERE{ 
    ?y vcard:Given ?g .
    FILTER regex(?g, "r", "i") 
}

#result
-------------
| g         |
=============
| "Rebecca" |
| "Sarah"   |
-------------

More example use FILTER.

  • Group Graph Pattern : where a set of graph patterns must all match

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    # a group graph pattern is delimited with {}

    {}  # empty graph pattern 
    PREFIX vcard:      <http://www.w3.org/2001/vcard-rdf/3.0#>

    SELECT ?y ?givenName
    WHERE { 
        {?y vcard:Family "Smith" .}
        {?y vcard:Given  ?givenName .}
    } 
    # Result same as previous query.

  • Optional Graph patterns : where additional patterns may extend the solution

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    # dataset
    <rdf:RDF                                                                                                                                                                                                            
      xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'
      xmlns:vCard='http://www.w3.org/2001/vcard-rdf/3.0#'
      xmlns:info='http://somewhere/peopleInfo#'
       >

      <rdf:Description rdf:about="http://somewhere/JohnSmith/">
        <vCard:FN>John Smith</vCard:FN>
        <info:age rdf:datatype='http://www.w3.org/2001/XMLSchema#integer'>25</info:age>
        <vCard:N rdf:parseType="Resource">
        <vCard:Family>Smith</vCard:Family>
        <vCard:Given>John</vCard:Given>
        </vCard:N>
      </rdf:Description>

      <rdf:Description rdf:about="http://somewhere/RebeccaSmith/">
        <vCard:FN>Becky Smith</vCard:FN>
        <info:age rdf:datatype='http://www.w3.org/2001/XMLSchema#integer'>23</info:age>
        <vCard:N rdf:parseType="Resource">
        <vCard:Family>Smith</vCard:Family>
        <vCard:Given>Rebecca</vCard:Given>
        </vCard:N>
      </rdf:Description>

      <rdf:Description rdf:about="http://somewhere/SarahJones/">
        <vCard:FN>Sarah Jones</vCard:FN>
        <vCard:N rdf:parseType="Resource">
        <vCard:Family>Jones</vCard:Family>
        <vCard:Given>Sarah</vCard:Given>
        </vCard:N>
      </rdf:Description>

      <rdf:Description rdf:about="http://somewhere/MattJones/">
        <vCard:FN>Matt Jones</vCard:FN>
        <vCard:N
        vCard:Family="Jones"
        vCard:Given="Matthew"/>
      </rdf:Description>

    </rdf:RDF>
    		 
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# OPTIONAL
PREFIX info:        <http://somewhere/peopleInfo#>
PREFIX vcard:      <http://www.w3.org/2001/vcard-rdf/3.0#>

SELECT ?name ?age
WHERE {
    ?person vcard:FN  ?name .
    OPTIONAL { ?person info:age ?age . FILTER ( ?age > 24 ) }
}

# result
-----------------------
| name          | age |
=======================
| "Becky Smith" |     |
| "Sarah Jones" |     |
| "John Smith"  | 25  |
| "Matt Jones"  |     |
-----------------------
  • Alternative Graph Pattern : where two or more possible patterns are tried
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    #dataset 
    @prefix foaf: <http://xmlns.com/foaf/0.1/> .
    @prefix vcard: <http://www.w3.org/2001/vcard-rdf/3.0#> .

    _:a foaf:name   "Matt Jones" .

    _:b foaf:name   "Sarah Jones" .

    _:c vcard:FN    "Becky Smith" .

    _:d vcard:FN    "John Smith" .
    		 
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# UNION
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX vCard: <http://www.w3.org/2001/vcard-rdf/3.0#>

SELECT ?name1 ?name2
WHERE
{
   { [] foaf:name ?name1 } UNION { [] vCard:FN ?name2 }
}

# result
---------------------------------
| name1         | name2         |
=================================
| "Matt Jones"  |               |
| "Sarah Jones" |               |
|               | "Becky Smith" |
|               | "John Smith"  |
---------------------------------
  • Patterns on Named Graphs, where patterns are matched against named graphs
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    # Default graph (ds-dft.ttl):
    @prefix dc: <http://purl.org/dc/elements/1.1/> .
    @prefix xsd: <http://www.w3.org/2001/XMLSchema#> .

    <ds-ng-1.ttl> dc:date "2005-07-14T03:18:56+0100"^^xsd:dateTime .
    <ds-ng-2.ttl> dc:date "2005-09-22T05:53:05+0100"^^xsd:dateTime .

    # Named graph (ds-ng-1.ttl):
    @prefix dc: <http://purl.org/dc/elements/1.1/> .

    [] dc:title "Harry Potter and the Philospher's Stone" .
    [] dc:title "Harry Potter and the Chamber of Secrets" .

    #Named graph (ds-ng-2.ttl):
    @prefix dc: <http://purl.org/dc/elements/1.1/> .

    [] dc:title "Harry Potter and the Sorcerer's Stone" .
    [] dc:title "Harry Potter and the Chamber of Secrets" .
    		 
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# query
PREFIX  xsd:    <http://www.w3.org/2001/XMLSchema#>
PREFIX  dc:     <http://purl.org/dc/elements/1.1/>
PREFIX  :       <.>

SELECT ?date ?title
{
  ?g dc:date ?date . FILTER (?date > "2005-08-01T00:00:00Z"^^xsd:dateTime )
  GRAPH ?g
      { ?b dc:title ?title }
}

# result
-----------------------------------------------------------------------------------------
| date                                      | title                                     |
=========================================================================================
| "2005-09-22T05:53:05+01:00"^^xsd:dateTime | "Harry Potter and the Sorcerer's Stone"   |
| "2005-09-22T05:53:05+01:00"^^xsd:dateTime | "Harry Potter and the Chamber of Secrets" |
-----------------------------------------------------------------------------------------


# specific graph 
PREFIX dc: <http://purl.org/dc/elements/1.1/>
PREFIX : <.>

SELECT ?title
{
  GRAPH :ds-ng-2.ttl
    { ?b dc:title ?title }
}

# result
---------------------------------------------
| title                                     |
=============================================
| "Harry Potter and the Sorcerer's Stone"   |
| "Harry Potter and the Chamber of Secrets" |
---------------------------------------------

# note that: 
GRAPH <IRI> { ... pattern ... }
GRAPH VAR { ... pattern ... }
 
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# FROM NAMED
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
PREFIX dc:  <http://purl.org/dc/elements/1.1/>
PREFIX :    <.>

SELECT *
FROM       <ds-dft.ttl>
FROM NAMED <ds-ng-1.ttl>
FROM NAMED <ds-ng-2.ttl>
{
   { ?s ?p ?o } UNION { GRAPH ?g { ?s ?p ?o } }
}

Producing Result Sets

SPARQL has four result forms:

  • SELECT – Return a table of results.
  • CONSTRUCT – Return an RDF graph, based on a template in the query.
  • DESCRIBE – Return an RDF graph, based on what the query processor is configured to return.
  • ASK – Ask a boolean query.

Pattern matching produces a set of solutions. This set can be modified in various ways:

  • Order By modifier: put the solutions in order
  • Projection modifier: choose certain variables
  • Distinct modifier: ensure solutions in the sequence are unique
  • Reduced modifier: permit any non-unique solutions to be eliminated
  • Offset modifier: control where the solutions start from in the overall sequence of solutions
  • Limit modifier: restrict the number of solutions
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