exists c, hc
c : Change
out : Output
t : Component.Valued × ID
hc : c ∈ out
ht : Change.target c = some t
⊢ t ∈ targets out
c : Change
out : Output
t : Component.Valued × ID
hc : c ∈ out
ht : Change.target c = some t
⊢ Change.Targets c t.1 t.2