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Requirements Specification of an Automotive System with Hybrid Sequence Charts. Radu Grosu CIS University of Pennsylvania Ingolf Krueger, Thomas Stauner TU Muenchen. Motivation.
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Requirements Specification of an Automotive System with Hybrid Sequence Charts Radu Grosu CIS University of Pennsylvania Ingolf Krueger, Thomas Stauner TU Muenchen
Motivation • The design of hybrid systems is a difficult task. One has to consider many different aspectslike data, behavior, architecture and distribution. • Moreover it usually involves people from different engineering disciplines. • Many modern SE methods like UML, ROOMand SDL recommend the use of visual specifications.
Motivation • In the projects BeQuest at TU Muenchen and CHARON at Upenn we developed HyCharts, a visual designlanguage 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.
Electronic Height Control System (BMW)(Informal Requirements Specification) • Whenever the chassis levelis belowa 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 filteredto eliminate noise, • The filtered value is read periodically by a controller which operates the compressor and the escape valves and resets thefilterwhen necessary, • A sensor tells the controller whether the car is in bend (in a curve).
EHC Architecture bend aHeight sHeight fHeight Filter D dReset reset EHC +
EHC Description by Trajectories sHeight fHeight aHeight reset time t t´ t´´
sHeight greater inside1 inside2 fHeight greater inside1 ins2 inside3 aHeight decrease constant reset low high time t t´ t´´ EHC Description by Timing Diagrams
down inTol greater a_dec inside2 inside1 a_const EHC with Hybrid Sequence Charts Filter D Control d2i t_o reset set dReset
cond2 cond1 Basic Segment of a HySC A B C i1 -> input x1,..,xi output y1,..,yj local z1,..,zk im-1-> i1 s1 cond1 im ... o1 on ... im-> o1 &..& on sm cond2 B
inBendC outBendC inBend outBend b2n n2b High Level Sequence ChartsEHC-Root
inTol outTol High Level Sequence Charts(outBend) outBendC i2i i2o o2i o2o
inTol outTol up outTol inTol down up down i2u High Level Sequence Charts(i2o and o2i) i2d d2i u2i
Filter Control inTol down inside greater a_const t_o set Basic Sequence Charts(i2d) D abv
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.