On improving efficiency of model checking through systematically ...

(init0)
init_0
((not p2 and p1)
or (p2 and not p1))
(ok and not init0) and
(y>=0 and x>=0
and -y+x+1>=0)
good_0
(y-x-1>=0)
and ((not p2 and p1)
or (p2 and not p1))
(not ok and not init0) and
(y+x-2>=0 and -y+x+2>=0
and y-x>=0);
bad_0
(not y-x-1>=0)
and ((not p2 and p1)
or (p2 and not p1))
Figure 3.5: A transformed automaton
1. The existence of if-then-else statement in Nbac dataflow
equations. A dataflow equation (assignment) in an Nbac model can
be as follows:
x’ = if (init0) then 0
else if (not init0) and ((not b1 and not b0) or (b1 and b0))
then x+1
else if (not init0) and true
and ((b1 and not b0) or (not b1 and b0))
then x
else 0;
Figure 3.6: A dataflow equation in Nbac model
where x: Integer; init0,b0,b1:Boolean.
Since PMC/Uppaal does not support if-then-else statement in assignments,
we have to model such statements in a reasonable way
in an XTG model. We remove the if-then-else statement from the
assignment by transforming it to a value expression containing only
numerical operators. Consider the following assignment:
x:= if a then x1
else if b then x2
else x3;
where x,x1,x2,x3: Boolean or Integer; a,b :Boolean.
Although there is else-if syntax, the Boolean conditions associated
with else-if component are already exclusive (this only holds for the
Nbac output model) 2 . The last else part is a fake just to fulfill the
2 claimed by the author of Nbac
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