Subject not used on every line of query - why?

Question

I am relatively new to SPARQL and struggling with the difference of the following two query examples:

PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT ?name ?email
WHERE {
  ?person a foaf:Person.
  ?person foaf:name ?name.
  ?person foaf:mbox ?email.
}

vs.

PREFIX mo: <http://purl.org/ontology/mo/>
PREFIX foaf:  <http://xmlns.com/foaf/0.1/>
SELECT ?name ?img ?hp ?loc
WHERE {
  ?a a mo:MusicArtist ;
     foaf:name ?name ;
     foaf:img ?img ;
     foaf:homepage ?hp ;
     foaf:based_near ?loc .
}

My question: why is the '?person' variable name in the first example needed on every line whereas the '?a' variable name in the second example is only used once?

I've closed this as a duplicate of [a question about the meaning of semicolon (;) in SPARQL queries](http://stackoverflow.com/questions/18214338/meaning-of-sparql-operator). The short answer is that `.` terminates a triple, and another pattern follows, but that `;` terminates a triple, and is followed by another predicate and object. so `a b c . a d e .` is the same as `a b c ; d e .` There's also a `,` that lets you terminate a triple, but follow with another object for the same property, so you can turn `a b c . a b d .` into `a b c, d .`. You can combine these, too, so that you can turn — Joshua Taylor, Sep 15 '15 at 15:32
`a p b . a p c . a q d . a q e.` into `a p b, c ; q d, e .`, which looks terrible on a single line, but can work quite nicely when formatted well. — Joshua Taylor, Sep 15 '15 at 15:33

score 0 · Accepted Answer · answered Sep 15 '15 at 13:05

It's a short hand. See that ";" at the end of the line? It means "next triple pattern uses the same subject as this one".

http://www.w3.org/TR/sparql11-query/#QSynTriples

?a a mo:MusicArtist ;
   foaf:name ?name ;
   foaf:img ?img ;
   foaf:homepage ?hp ;
   foaf:based_near ?loc .

is a block that is exactly the same triple patterns as

?a a mo:MusicArtist .
?a foaf:name ?name .
?a foaf:img ?img .
?a foaf:homepage ?hp .
?a foaf:based_near ?loc .

It's just syntax.

Subject not used on every line of query - why?

1 Answers1