On improving efficiency of model checking through systematically ...

not use that format for the reason that it is used by Nbac for visualization
purpose only, meaning that model details are necessarily reduced to serve
that purpose.
An Nbac output model contains all the components that have been described
in Section 2.1 including variable declaration, dataflow equation, assertion,
initial and final condition. Therefore, we will not repeat those parts
here.
The major difference between an Nbac input model and output model
is the presence of an explicit automaton or control structure in the output
model. This control structure is the foundation for our transformation
between models. It is defined by a set of locations and edges:
• Locations: A location is associated with an invariant, which is a
Boolean expression that gives the set of states represented by the location.
• Edges: An edge is associated with with a guard, which is a Boolean
expression on state and input variables that indicates under which
condition the edge can be taken.
The union of all invariants of the locations indicates the considered statespace.
The union of all guards of the edges allows to enforce the behavior
of the global system.
Figure 3.1 presents an example of the control structure specified in an
Nbac output model.
automaton
location bad_0 : (not ok and not init0) and (y+x-2>=0 and -y+x+2>=0
and y-x>=0);
location init_0 : (init0) and true;
location good_0 : (ok and not init0) and (y>=0 and x>=0 and -y+x+1>=0);
edge (init_0,good_0) : true and true and ((not p2 and p1)
or (p2 and not p1));
edge (good_0,bad_0) : true and (y-x-1>=0) and ((not p2 and p1)
or (p2 and not p1));
edge (good_0,good_0) : true and (not y-x-1>=0) and ((not p2 and p1)
or (p2 and not p1));
Figure 3.1: An example of control structure in Nbac output model
The control structure in Figure 3.1 contains three locations and three
edges. We can see that there is no assignment in this automaton besides locations,
edges, invariants and guards. Assignments are put in the transition
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