On 12/08/14 11:24, Miguel Bento Alves wrote:
Hi Andy,
with your example I can extract the triples but I can’t extract the
sub-queries. Is there a simple way to extract the sub-queries from a query
pattern?
Miguel
The code needs to walk down the syntax tree from the top looking for
ElementSubQuery that signals a subquery.
If in the algrebra, its a case of looking for a "modifier" but somtimes
there just isn't a subquery any more:
SELECT * { { SELECT * {?s ?p ?o}} }
==>
(bgp (triple ?s ?p ?o))
The inner "SELECT *" did nothing and no sign of it remains.
Andy
On 08 Aug 2014, at 21:10, Andy Seaborne <a...@apache.org> wrote:
On 08/08/14 10:15, Miguel Bento Alves wrote:
Hi all,
In a Sparql query, we can extract the query pattern ( q.getQueryPattern() ).
For instance, in the sparql command:
Select ?x ?p ?z where {?x ?p ?y . ?x <eg:p> ?z.}
we can extract:
{ ?x ?p ?y .
?x <eg:p> ?z
}
Is there anyway to extract as TriplePattern?
If you are working with the parsed object, you have to test/cast the query
pattern:
Query query = QueryFactory.create("SELECT*{?s ?p ?o}") ;
ElementGroup el = (ElementGroup)query.getQueryPattern() ;
Element bgp = el.getElements().get(0) ;
ElementPathBlock elp = (ElementPathBlock)bgp ;
PathBlock pb = elp.getPattern() ;
for ( TriplePath tp : pb ) {
Triple t = tp.asTriple() ;
if ( t == null )
System.err.println("Path: "+tp.getPath()) ;
else
System.out.println(t) ;
}
Note in the syntax, you can have paths: { ?x :p/:q ?y }
It is much easier to work with algebra.
Op op = Algebra.compile(query.getQueryPattern()) ;
System.out.println(op) ;
OpBGP x = (OpBGP)op ;
for ( Triple t : x.getPattern() ) {
System.out.println("Algebra: -- "+t) ;
}
Also, we can extract the vars ( PatternVars.vars(qf.getQueryPattern()) ). Is
it possible to extract the the non-vars?
There's no code written - you can take a copy of the the code behind
PatternVars and modify that.
Miguel
