ASK
Applications can use the ASK form to 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.
@prefix foaf: <http://xmlns.com/foaf/0.1/> .
_:a foaf:name "Alice" .
_:a foaf:homepage <http://work.example.org/alice/> .
_:b foaf:name "Bob" .
_:b foaf:mbox <mailto:bob@work.example> .
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
ASK { ?x foaf:name "Alice" }
true
The SPARQL Query Results XML Format form of this result set gives:
<?xml version="1.0"?>
<sparql xmlns="http://www.w3.org/2005/sparql-results#">
<head></head>
<boolean>true</boolean>
</sparql>
On the same data, the following returns no match because Alice's mbox is not mentioned.
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
ASK { ?x foaf:name "Alice" ;
foaf:mbox <mailto:alice@work.example> }
false
Copyright © 2013 W3C® (MIT, ERCIM, Keio, Beihang). This software or document includes material copied from or derived from SPARQL 1.1 Query.