Towards a Platform for Widespread Embedded Intelligence - ERCIM

New Tool to Design the Behaviour
of Embedded Systems
by Jan Friso Groote
Can a car drive faster than the speed limit the cruise control indicates? Are
computerised protocols between planes and air traffic control safe?
Communication between software components in cars, planes and other intelligent
embedded systems is often very complex and prone to errors. The Design and
Analysis of Systems group at Eindhoven University of Technology is releasing
a new toolset, mCRL2, to improve the quality of embedded system design.
An embedded system can roughly be
described as some piece of equipment
with one or more computer processors in
it. The processor allows this equipment
to behave with an amazing level of intelligence.
Copiers order their own paper
and cars actively avoid accidents. The
end of this is not in sight. The behaviour
of such systems will become far more
advanced than it is today.
The downside of this is that the
behaviour of systems becomes so complex
that we cannot easily understand it
anymore. As a consequence, most features
of contemporary equipment remain
unused. But it is even worse. Because the
system components are exhibiting more
and more complex behaviour, they do
not always understand each other. The
consequence is that intelligent systems
often behave erraticly. For modern TV
sets a 'misunderstanding' between the
components occurs every minute in each
television. Much effort goes into
building internal firewalls to restrain
these flaws so they are not noticed by
those watching TV.
Now that the behaviour of systems is
becoming so complex, it has become an
important research topic. Just as in other
engineering disciplines, complexity is
tackled by making models. These
behavioural models describe the potential
behaviour of the system, ie which
interactions can take place when.
Typical examples are sending messages,
pressing buttons, activating actuators
and reading sensors. Questions that must
be answered are: are all messages properly
processed; can a car ever be
instructed to drive faster than the speed
limit of the cruise control; does a copier
always order paper in time or is it pos-
sible that it orders twice the amount
needed due to message duplication?
The major challenge to answering such
questions is the 'state space explosion'.
Even relatively simple behavioural
State spaces, visualized by the mCRL2 toolset.
models give rise to millions of states. In
order to show that a system behaves correctly,
all these states must be investigated.
It goes without saying that analysis
tools are essential here. It is impossible
to carry out the analysis of an
industrial behavioural model by hand,
but manual manipulation and human
insight is also essential to reduce it to a
manageable size.
SPECIAL THEME: Embedded Intelligence
At Eindhoven University of Technology,
in close cooperation with CWI in
Amsterdam, we are developing a mathematical
methodology accompanied with
tools to model and analyse the (discrete)
behaviour of embedded systems. The
method is called mCRL2, where CRL
stands for Common Representation
Language. The methodology is based on
process algebra, extended with data
types. The method has been applied to
almost all major embedded system
industries within the Netherlands.
Furthermore, it is being taught at several
universities.
The major idea underlying the methodology
is to transform each model to a
normal form, a so called linear process.
Due to its simple structure, a linear process
is very amenable to symbolic
manipulation and simplification. For
instance, by detecting confluent
Picture: TU/e.
ERCIM News No. 67, October 2006 27