s_0\wedge EX(E[\neg s_0 U(s_0\wedge\neg s_0)]\vee       EG\neg s_0))]$, $HandleEU$ is called with $L_0$ to construct an $EU graph$ $G_0=\langle N,E,L_0\rangle$ with id $0$ (see Figure 00) and return a labeling function $$L_f=\{(s_0,0),(s_0,0),(s_0,0),(s_0,0),(s_0,0)\}.$$      ![](newfig000.eps)  Since $s_0$ is labeled by $L_f$ with an ID expression $0$ instead of $0$ (i.e., $true$), we need to test whether the ID expression $0$ can be evaluated true at $s_0$ by calling $TestWG$ with $s_0$ and $G_0$. It's easy to see that, essentially $TestWG$ would be testing whether some communication trace (with bounded lengt