Chapter 7. MDSD and SysML 157
Constraints are properties in sub-systems (that is, blocks) named
ConstraintProperty and are typed by <<constraintBlock>>. A constraint block
defines an expression and the attributes that represent its parameters. SysML
does not prescribe any language to represent the expressions or provide a
solver for it. This setting is typically offered within the usage of a particular
tool.
The RSW uses a set of analytical constraints to verify that the system is
properly calibrated (requirement System Calibration in Figure 7-2 on
page 148). Three constraints are shown in Figure 7-7:
– The constraint SensorEffectiveRange computes an operational range for
the sensor, based on some of its parameters.
– Similarly, the constraint WindshieldIREffectiveRange computes an
operating range for infrared sensor that can be compared with the one
computed for the sensor.
– Finally the constraint SensorWindshieldRangeCompare is used to compare
the above values.
Figure 7-7 Definition of constraint blocks for the Rain Sensing Wiper system
