Chapter 14. Individuals

In philosophy and logic, individuals are specific real-world entities that can be instances of types ("universals"), but are not types themselves. In contrast, in SysML2, a "singleton" occurrence type representing a specific item or action is called an individual.

The following example illustrates the use of individual types and properties in SysML2:

part def Wheel;
part def Car {
  part frontLeftWheel : Wheel;
  part frontRightWheel : Wheel;
  part rearLeftWheel : Wheel;
  part rearRightWheel: Wheel;
}
// a part type restricted to a singleton population
individual part def Wheel123 :> Wheel;
// an individual car with the same wheel in different positions at different times
individual part def Car345 :> Car {
  timeslice {
    // an individual property having the individual Wheel123 as its value
    individual part redefines frontLeftWheel : Wheel123;
  }
  then timeslice {
    // another individual property having the individual Wheel123 at a later time
    individual part redefines rearRightWheel : Wheel123;
  }
}