SPARQL Basics

Variable

A name starts with "?", e.g. ?mbox

WHERE Clause

PREFIX foaf:   <http://xmlns.com/foaf/0.1/>
SELECT ?name ?mbox
WHERE
  { ?x foaf:name ?name .
    ?x foaf:mbox ?mbox }

?x foaf:name ?name matches a triplet in a KG. ?x refers to the head entity. foaf:name matches a relationship. ?name refers to the tail entity. The period operator . means "AND".

Operators

Semicolon

Triple patterns with a common subject can be written so that the subject is only written once and is used for more than one triple pattern by employing the ";" notation.

?x  foaf:name  ?name ;
    foaf:mbox  ?mbox .

is equivalent to

?x  foaf:name  ?name .
?x  foaf:mbox  ?mbox .

Square brackets

It is a syntax for blank nodes.

Subject case

[ :p "v" ] :q "w" .

is equivalent to

_:b57 :p "v" .
_:b57 :q "w" .

Object case

:x :q [ :p "v" ] .

is equivalent to

:x  :q _:b57 .
_:b57 :p "v" .

References

1. W3C: SPARQL Specifications

2. Stack Overflow: Meaning of SPARQL Operator

3. Stack Overflow: Meaning of square brackets “[]” when querying RDF with SPARQL