The role of a watchdog is not to attack people or to chase people away. A watchdog's purpose is to sound the alarm, just like your conventional home security system, when he sees someone do something that you really need to know about. For example, if a stranger walks into your backyard, or tampers with your cars, or fiddles with your front gate, those are things you need to know about. On the other hand, if a jogger or a cat pass on the sidewalk, the mailman goes by, or someone shouts in the yard next door, there is no sense in your dog barking at those things.
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