This HTML5 document contains 34 embedded RDF statements represented using HTML+Microdata notation.

The embedded RDF content will be recognized by any processor of HTML5 Microdata.

Subject Item

n12:this

foaf:made

n2:VirtTipsAndTricksGuideSPARQLLOADServiceUsage

Subject Item

n6:this

sioc:creator_of

n2:VirtTipsAndTricksGuideSPARQLLOADServiceUsage

Subject Item

n17:item

n18:services_of

n2:VirtTipsAndTricksGuideSPARQLLOADServiceUsage

Subject Item

n14:this

sioc:creator_of

n2:VirtTipsAndTricksGuideSPARQLLOADServiceUsage

Subject Item

n7:VOS

sioc:container_of

n2:VirtTipsAndTricksGuideSPARQLLOADServiceUsage

atom:entry

n2:VirtTipsAndTricksGuideSPARQLLOADServiceUsage

atom:contains

n2:VirtTipsAndTricksGuideSPARQLLOADServiceUsage

Subject Item

n2:VirtTipsAndTricksGuideSPARQLLOADServiceUsage

rdf:type

sioct:Comment atom:Entry

dcterms:created

2017-06-13T05:36:13.610453

dcterms:modified

2017-06-29T07:41:36.521079

rdfs:label

VirtTipsAndTricksGuideSPARQLLOADServiceUsage

foaf:maker

n11:this n12:this

dc:title

VirtTipsAndTricksGuideSPARQLLOADServiceUsage

opl:isDescribedUsing

n4:rdf

sioc:has_creator

n6:this n14:this

sioc:content

%META:TOPICPARENT{name="VirtTipsAndTricksGuide"}% ---+Virtuoso SPARQL LOAD Service ---++What? Using SPARQL LOAD service to get remote endpoint's description. ---++Why? Provides additional data that might be useful such as: if a local server knows what syntax extensions are supported by the remote SPARQL endpoint for ex.: <code> http://example.com/sparql </code> then it can improve the compilation of SPARQL queries that contain clauses like: <verbatim> SERVICE <http://example.com/sparql> {...} . </verbatim> ---++How? To get the description of remote endpoint, one should run the following statement at its local server: <verbatim> SPARQL LOAD SERVICE <http://example.com/sparql> DATA; </verbatim> The retrieved description will be stored in local RDF storage as a part of "<code> System Metadata" graph </code>, so the user calling this statement should have appropriate write permissions. ---+++Example 1 Suppose the following query: <verbatim> INSERT INTO <http://voc.wkd.de> { ?s owl:sameAs ?o. } WHERE { GRAPH <http://voc.wkd.de> { ?s rdf:type skos:Concept.} SERVICE <http://de.dbpedia.org/sparql> { SELECT ?o WHERE { ?s <http://www.w3.org/2002/07/owl#sameAs> ?o . FILTER REGEX(str(?o), "^http://dbpedia.org") . } LIMIT 10 } } </verbatim> 1 Next we will bound the ?s in the graph part and the ?s in the scope of the service part: For every concept ?s in the graph &lt;http://voc.wkd.de&gt; we want to retrieve the <code> owl:sameAs </code> elements in the service <code> &lt;http://de.dbpedia.org/sparql&gt; </code> , so for ex: * Locally there is the following triple: <verbatim> { dbpedia:A a skos:Concept } </verbatim> * In dbpedia there are the following triples: <verbatim> { dbpedia:B owl:sameAs dbpedia:C. dbpedia:A owl:sameAs dbpedia:D. } </verbatim> * The expected result we want to be: <verbatim> { dbpedia:A owl:sameAs dbpedia D. } </verbatim> 1 The simplest way to make ?s interrelated is to alter the select statement and to add <code> ?s </code> into its result set: <verbatim> INSERT INTO <http://voc.wkd.de> { ?s owl:sameAs ?o. } WHERE { GRAPH <http://voc.wkd.de> { ?s rdf:type skos:Concept.} SERVICE <http://de.dbpedia.org/sparql> { SELECT ?s ?o WHERE { ?s <http://www.w3.org/2002/07/owl#sameAs> ?o . FILTER REGEX(str(?o), "^http://dbpedia.org") . } LIMIT 10 } } </verbatim> 1 The change will affect to the following: 1 <code> ?s from service </code> and <code> ?s from graph &lt;&gt; {} </code> will both appear at the same scope and the equality between them will be required by the semantics. 1 The optimizer will understand that it's better to pass the <code> ?s </code> as parameter to the service instead of selecting all pairs of <code> ?s </code> and <code> ?o </code> and filter them at the main query server. 1 The code generator will try to write a code for sending a query to <code> http://de.dbpedia.org/sparql </code> but it may fail if it are not known the capabilities of SPARQL compiler at <code> http://de.dbpedia.org/sparql </code> , so before the first compilation, one should execute the following statement: <verbatim> SPARQL LOAD SERVICE <http://de.dbpedia.org/sparql> DATA; </verbatim> * The effect of executing the <code> SPARQL LOAD SERVICE </code> statement will be: 1 Recognize what syntax extensions are supported by the compiler inside <code> http://de.dbpedia.org/sparql </code> service endpoint. E.g., whether that endpoint can deal with external parameters. 1 Will write small description of the endpoint to local metadata but will not try to copy any data stored remotely to the local storage. 1 <b>Important Note</b>: that if the graph <code> &lt;http://voc.wkd.de&gt; { ?s rdf:type skos:Concept.} </code > will produce many values for <code>?s</code>, there will be many requests to dbpedia, and the sum of round-trip latencies will be high. In some cases it may be faster to get one big list of <code> ?s ?o pairs </code> from <b>dbpedia</b> and then search in local graph. To change the order of execution to "remote first" variant, the order of clauses should be changed to: <verbatim> INSERT INTO <http://voc.wkd.de> { ?s owl:sameAs ?o. } WHERE { SERVICE <http://de.dbpedia.org/sparql> { SELECT ?s ?o WHERE { ?s <http://www.w3.org/2002/07/owl#sameAs> ?o . FILTER REGEX(str(?o), "^http://dbpedia.org") . } LIMIT 10 } GRAPH <http://voc.wkd.de> { ?s rdf:type skos:Concept.} } </verbatim> ---++Related * [[VirtTipsAndTricksGuide][Virtuoso Tips and Tricks Collection]] * [[http://docs.openlinksw.com/virtuoso/rdfsparql.html][Virtuoso Documentation]]

sioc:id

7e993b38b037d69f3c5ac536ac70b3d7

sioc:link

n2:VirtTipsAndTricksGuideSPARQLLOADServiceUsage

sioc:has_container

n7:VOS

n18:has_services

n17:item

atom:title

VirtTipsAndTricksGuideSPARQLLOADServiceUsage

sioc:links_to

n8:sparql n15:html n21:de n22: n23:sparql

atom:source

n7:VOS

atom:author

n12:this

atom:published

2017-06-13T05:36:13Z

atom:updated

2017-06-29T07:41:36Z

sioc:topic

n7:VOS