Interaction Operator Kind is an enumeration designating the different kinds of operators of combined fragments. The different types are seq, alt, opt, break, par, strict, loop, region, neg, assert, ignore and consider.
- Alternatives
Alt represents a choice of behavior by evaluating guard conditions associated to each operand. At most one of the operands will be chosen.
An operand guarded by else designates a guard that is the negation of the disjunction of all other guards in the enclosing combined fragment.
- Option
Opt represents a choice of behavior where either the (sole) operand happens or nothing happens.
- Break
Break represents a breaking scenario that is performed instead of the remainder of the enclosing interaction fragment.
- Parallel
Par represents a parallel merge between the behaviors of the operands. The occurrence specifications of the different operands can be interleaved in any way as long as the ordering imposed by each operand as such is preserved.
- Weak Sequencing
Seq represents a weak sequencing between the behaviors of the operands defined by three properties:
1. The ordering of occurrence specifications within each of the operands are maintained in the r esult.
2. Occurrence specifications on different lifelines from different operands may come in any order.
3. Occurrence specifications on the same lifeline from different operands are ordered such that an
occurrence specification of the first operand comes before that of the second operand.
- Strict Sequencing
Strict represents a strict sequencing between the behaviors of the operands.
- Negative
Neg represents an invalid interaction operand.
- Critical Region
Critical represents a region that is treated atomically by the enclosing fragment . A critical region means that the traces of the region cannot be interleaved by other occurrence specifications (on those lifelines covered by the region).
- Ignore / Consider
Consider and Ignore cases require lists of pertinent messages to be specified.
Ignore designates that there are some message types that are not shown within this combined fragment. These message types can be considered insignificant and are implicitly ignored if they appear in a corresponding execution.
Consider designates which messages should be considered within this combined fragment. This is equivalent to defining every other message to be ignored.
- Assertion
Assert specifies that the sequences of the operand of the assertion are the only valid continuations for a given message. All other continuations are invalid.
Assertions are often combined with Ignore or Consider.
- Loop
Loop specifies that the operand will be repeated a number of times. The guard may include a lower and an upper number of iterations of the loop as well as a boolean expression.