Requirements%20Specification%20of%20an%20Automotive%20System%20with%20Hybrid%20Sequence%20Charts

1
Requirements Specification of an Automotive
System with Hybrid Sequence Charts

• Radu Grosu
• CIS University of Pennsylvania
• Ingolf Krueger, Thomas Stauner
• TU Muenchen

2
Motivation

• The design of hybrid systems is a difficult task.
  One has to consider many different aspects like
  data, behavior, architecture and distribution.
• Moreover it usually involves people from
  different engineering disciplines.
• Many modern SE methods like UML, ROOM and SDL
  recommend the use of visual specifications.

3
Motivation

• In the projects BeQuest at TU Muenchen and CHARON
  at Upenn we developed HyCharts, a visual design
  language supporting the hierarchic specification
  of architecture and behavior of hybrid systems.
• The aim of this work is to complement HyCharts
  with HySequenceCharts, a visual requirements
  language supporting the hierarchic specification
  of interaction between hybrid systems.

4
Electronic Height Control System (BMW)(Informal
Requirements Specification)

• Whenever the chassis level is below a certain
  bound, a compressor is used to increase it,
• If the level is too high, air is blown off by
  opening an escape valve,
• The chassis level is measured by sensors and
  filtered to eliminate noise,
• The filtered value is read periodically by a
  controller which operates the compressor and the
  escape valves and resets the filter when
  necessary,
• A sensor tells the controller whether the car is
  in bend (in a curve).

5
EHC Architecture
bend
aHeight
sHeight
fHeight
Filter
D
dReset
reset
EHC

6
EHC Description by Trajectories
sHeight
fHeight
aHeight
reset
time
t
t
t
7
EHC Description by Timing Diagrams
8
EHC with Hybrid Sequence Charts
D
Filter
Control
d2i
t_o
reset
set
dReset
9
Basic Segment of a HySC
A
B
C
input x1,..,xi output y1,..,yj local z1,..,zk
i1 -gt
im-1-gt
i1
s1 cond1
im
...
o1
on
...
im-gt o1 .. on
sm cond2
B
10
High Level Sequence ChartsEHC-Root
11
High Level Sequence Charts(outBend)
outBendC
i2i
i2o
o2i
o2o
12
High Level Sequence Charts(i2o and o2i)
i2d
d2i
u2i
13
Basic Sequence Charts(i2d)
D
abv
14
Conclusions

• We introduced a new visual requirements
  specification language HySequenceCharts for
  describing interaction between hybrid systems.
• HySequence charts can be advantageously used in
  the early phases of the development process.
• In particular, in the requirements capture phase,
  they improve the dialog between customers and
  application experts.
• The semantics for HySC is very different from the
  well known MSC. Most notably, we use shared
  variables and a global continuous clock.