Problems withtcs T1 S1 T2 S2 (Compositionality) T1 T2 9 S1 $2 Existing work on verifying TCS: either is not compositional, or limIts applications.(Compositionality) T1 || T2  S1 || S2 T1  S1 T2  S2  Problems with T  S Existing work on verifying T  S : either is not compositional, or limits applications