Triplifier for SPARQL queries

[justin2004]

I'm working on a new triplifier for SPARQL query files.

Here is the thinking so far...

If you point SPARQL Anything at this file:

select ?o ?o2
where {
?s ?p ?o
optional {?o a ?o2}
} limit 10

Internally it'll use Jena's qparse functionality to turn that into SPARQL algebra (serialized as SSE):

(slice _ 10
  (project (?o ?o2)
    (leftjoin
      (bgp (triple ?s ?p ?o))
      (bgp (triple ?o <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?o2)))))

And then that will be triplified like this:

@prefix xyz:    <http://sparql.xyz/facade-x/data/> .
@prefix fx:   <http://sparql.xyz/facade-x/ns/> .
@prefix rdf:   <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
[ a fx:root , xyz:slice  ;
  rdf:_1 "_" ;
  rdf:_2 10 ;
  rdf:_3 [ a xyz:project  ;
           rdf:_1 [ rdf:_1 "?o" ;
                    rdf:_2 "?o2"  ] ;
           rdf:_2 [ a xyz:leftjoin ;
                    rdf:_1 [ a xyz:bgp ;
                             rdf:_1 [ a xyz:triple ;
                                      rdf:_1 "?s" ;
                                      rdf:_2 "?p" ;
                                      rdf:_3 "?o" ] ] ;
                    rdf:_2 [ a xyz:bgp ;
                             rdf:_1 [ a xyz:triple ;
                                      rdf:_1 "?o" ;
                                      rdf:_2 <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ;
                                      rdf:_3 "?o2" ] ] ] ] ]

At the moment SPARQL Anything only goes in the "uplift" direction (source data to RDF) and not in the "lower" direction (RDF back to source data) but I am also thinking about making an untriplify() method to take the RDF back to SSE and finally to SPARQL.