Stabat Mater in F minor, D 383, is a musical setting of the "Stabat Mater" sequence, composed by Franz Schubert in 1816. It is scored for soprano, tenor and bass soloists, SATB choir, 2 flutes, 2 oboes, 2 bassoons, contrabassoon, 2 french horns, 3 trombones, violin I and II, viola, cello and double bass.
Franz Schubert could play the violin
The context only states that the composition consists of a violin, it doesn't say that Franz Schubert could play a violin. He may have got someone else to play it for him. The system likely assumed because the piece contains a violin, Franz Schubert must be able to play it. 
( z0 possible :ARG1 ( z1 play :ARG0 ( z2 person :name ( z3 name :op "Franz" :op "Schubert" ) ) :ARG2 ( z4 violin ) ) )
(z0 / possible-01
    :ARG1 (z1 / play-11
              :ARG0 (z2 / person
                        :name (z3 / name
                                  :op1 "Franz"
                                  :op2 "Schubert"))
              :ARG2 (z4 / violin)))
Franz Schubert could play the violin
z3 :op1 0
z2 :name z3
z3 :op2 1
z0 :ARG1 z1
z1 :ARG0 z2
z1 :ARG2 z4