InterruptibleActivityRegion missing default timeout for interrupting edges

Goal

Define a portable default timeout that governs how long an interrupting edge may wait before forcing cancellation of an InterruptibleActivityRegion.

Constraints and uncertainty

• The UML 2.x specification describes InterruptibleActivityRegion and interrupting edges but does not prescribe a default timeout duration.
• AcceptEventAction can consume time events via TimeExpression, yet the standard provides no universal clock or scheduling guarantee.
• Cancellation propagation order and exception handling are delegated to the execution environment, leading to inconsistent runtime semantics across tools and code generators.

Open questions

1. What mechanism can supply a portable default timeout without extending the UML metamodel?
2. How should code generators expose timeout configuration to modelers?
3. Which UML tools currently implement a configurable timeout for interrupting edges?