On improving efficiency of model checking through systematically ...

• Hytech [1] is an automatic tool for the analysis of embedded systems.
HyTech computes the condition under which a linear hybrid system
satisfies a temporal requirement. It was developed at Cornell University
and improvements were added at University of California, Berkeley.
Although model checking is successfully applied in the area of hardware
and protocol verification, its use in software engineering is limited. The
most significant limitation of model checking in practice is the potential
state space explosion when it is applied to moderate and large size systems.
Section 1 of [16] provides with a simple example to exemplify the state space
explosion problem. In order to tackle this problem, abstraction techniques
have been sought to avoid exhaustive state space exploration. The general
idea of abstraction is that the state space of the system is reduced to a
smaller one, an abstract model, so that the verification is feasible. More
precisely, the model checker will verify the abstract model rather than the
original one, then the result obtained from verification on the abstract model
is concluded for the original model.
A practical issue arising is that how we can employ abstraction technique
into model checkers. A natural direction is to put abstraction technique into
the model checking algorithm. This involves defining an abstraction function
(to map concrete values to abstract values) suitable for the property to be
verified, constructing the abstract model and relating the verification results
to the behavior of the original (concrete) model[12]. This is not an easy
task especially for real-time models. Integrating abstraction technique into
an existing model checker is even more difficult.
Another possibility to employ abstraction in model checkers is to make
use of existing technology, i.e to use a tool that provides abstraction function
to generate abstract models and then feed those models into the model
checker under considering.
This thesis reports the work of a master project, which was originally
part of the larger project aimed at the theoretical and practical development
of a verification algorithm for real-time embedded systems based on a
combination between two tools Nbac and PMC:
• Nbac is a model checker developed in Verimag, France to prove safety
properties of synchronous programs. The highlight of Nbac is that it
employs an abstraction technique to reduce the state space and thus
scale up the size of systems that can be verified.
• PMC is a model checker developed in TU Delft to verify fair-TCTL
properties of real-time systems. Although the application area of PMC
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