On improving efficiency of model checking through systematically ...

The safety property to prove is x ≥ y. It is readily seen that the system
meets the safety property.
We choose this example as one of our case study in order to get an insight
on its models due to the simplicity of the system. Thus, we can trace the
output model manually to check whether or not the transformation tool
works properly.
The tiny example is originally specified in Nbac input language. Therefore,
the meaning of the model is very straightforward. See Appendix A.1
Two input variables p1,p2 was added just to see how assertion is generated
and the impact of input variable in the model.
This example is categorized as infinite system caused by unbounded Integer
variables. If we let the system run for a long time, x, y will exceed the
bounded Integer value.
4.2 Asynchronous Reader/Writer Algorithm
In [11] J. Chen and A. Burns describe an algorithm that implements a
fully asynchronous reader/writer algorithm which addresses the problems
of blocking and priority inversion within multi processor real-time systems.
The approach is conceived from the concept of process consensus in which
the writer and the reader come to an agreement on accessing the shared
data before proceeding to carry out their respective data operations. The
PMC/Uppaal model of this algorithm for one reader and the writer is presented
in Figure 4.2.
In Figure 4.2, there are two graphs: one for the Reader process and
one for the Writer process. The algorithm uses shared variables L1, L2,
P refer1, P refer2, Precon between Reader and Writer to control these
processes.
The safety property states that whenever the writer and the reader are
actually in the state of writing and reading simultaneously the writer and the
reader index must be unequal. This property is specified in Uppaal as “A[ ]
not (Reader.reading and Writer.writing and Reader.ridx==Writer.widx)”.
This algorithm is originally modeled in PMC. It is then transformed manually
to make it an Nbac input model. This step increases the physical size
of the model significantly. Then Nbac generates an output model from its
input and thus increases the size of the model even more.
This case study is categorized as finite system because all variables are
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