X ⊑ F S Y S ≡ t r a c e s ( S Y S ) ⊆ t r a c e s ( X ) ∧ f a i l u r e s ( S Y S ) ⊆ f a i l u r e s ( X ) {\displaystyle X\sqsubseteq _{F}SYS\equiv traces(SYS)\subseteq traces(X)\wedge failures(SYS)\subseteq failures(X)}
