#PREFIX apf:     <http://jena.hpl.hp.com/ARQ/property#>
#PREFIX  apf:    <java:com.hp.hpl.jena.query.pfunction.library.>
PREFIX  apf:    <java:com.hp.hpl.jena.sparql.pfunction.library.>

PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX :    <http://example/>

SELECT *
{ 
    ?a :q ?b .
    ?a apf:bnode ?label

##     # Case 1: Filter and BGPs.
##     # No join.
##     FILTER(?x + ?w)
##     FILTER(?a)
##     FILTER(?w)
##     :x1 :p ?v ;
##         :q ?w ;
##         :q ?x .
##     FILTER(true)

##     # Case 2 : Filter and joins
##     FILTER(?x + ?w)
##     FILTER(true)
##     { :x :p ?a }
##     FILTER(?a)
##     FILTER(?ZZZ)
##     FILTER(?w)
##     :x1 :p ?v ;
##         :q ?w ;
##         :q ?x .

##     # Case 3: OPTIONAL and unbound
##     :x :p ?v 
##     OPTIONAL { :x :q ?w }
##     FILTER(?v)
##     FILTER (!bound(?w) )

##     # Case 4: OPTIONAL + Filters
##     :x :p ?v 
##     OPTIONAL { :x :q ?w . FILTER(true) FILTER(?v)  FILTER(?w) }
}