Exploring RDF data with SPARQL

Getting a list of types

A good place to start is finding out what kinds of things are in the data:

sparql --data ../social.ttl --query types.sparql

query: 
SELECT DISTINCT ?type 
WHERE {
    [] a ?type
}
results: 
--------------------------------------
| type                               |
======================================
| <http://purl.org/dc/dcmitype/Text> |
| <http://xmlns.com/foaf/0.1/Person> |
--------------------------------------

DESCRIBE queries

We can use a DESCRIBE query to get basic information about an individual. Exactly what data DESCRIBE will return is up to the particular SPARQL implementation, but it is often simply every statement in which the specified entity is the subject. We don’t know any individuals in the dataset, so we’ll pick a random individual of a type we’re interested in:

sparql --data ../social.ttl --query describe.sparql

query: 
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
DESCRIBE ?subject
WHERE {
    ?subject a foaf:Person
} LIMIT 1
results: 
@prefix dc:      <http://purl.org/dc/terms/> .
@prefix rdfs:    <http://www.w3.org/2000/01/rdf-schema#> .
@prefix dctype:  <http://purl.org/dc/dcmitype/> .
@prefix foaf:    <http://xmlns.com/foaf/0.1/> .
@prefix rdf:     <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
 
<http://ca.linkedin.com/pub/matthew-links/44/381/647>
    rdf:type      foaf:Person ;
    foaf:knows    <http://www.linkedin.com/pub/mark-wilkinson/1/674/665> ;
    foaf:knows    <http://elmonline.ca/luke> ;
    foaf:name     "Matt Links" .

Notice the LIMIT clause in the query. Also notice that the query returned RDF, rather than variable bindings.