When an agent has a routine that can serve some purpose, e.g., to achieve a goal, we say that the agent has an ability to achieve that goal. In the context of system design, this goal may equate to a requirement, in which case the routine can be see as one of many high-level design options. In this formulation, an actor has the ability to do something if it has a routine for it. Having ability does not necessarily imply that one can achieve something all by oneself. Various degrees of delegation and external dependency may be involved.
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