Created attachment 271 [details]
Model

Change the old verification message: 

Location Derive._id1
[ Derive.x=0 Derive.y=1 Integrate.dt=0 Sample.t=0 #time=0 ]
Integrate.x=0 Integrate.y=1 Sample.x=0 Sample.y=1 
violates model sanity with transition
Derive._id0->Derive._id1 { 1, tau, y := 1 }

Using the new verification message design:

Message: violates model sanity with transition
The error location is showed in the model (GUI).