Project(
        Union(
              BGP(
                  triple(variable(s), uri<http://example.org#p1>, variable(v1))
              ) ,
              BGP(
                  triple(variable(s), uri<http://example.org#p2>, variable(v2))
              )
        ) ,
        Variables([ variable(s), variable(v1), variable(v2) ])
)
