In my text book I saw the sentence: If a request is made to a web service, then the response will be returned within 5 seconds or the service is under DoS attack.I cannot understand the usage of or in this sentence. Is it an exclusive or meaning that if the response will be returned within 5 seconds then there is no possibility of a DoS attack? Or does it just mean that if no response will be returned in 5 seconds, the service is under DoS attack. I will appreciate any help on understanding this sentence.
I don't think it's an exclusive or, because you can be under attack and still get a response within 5 seconds. I think what you have here is an inclusive disjunction, which you can read about here.
A = The response will be returned within 5 seconds.
B = The service is under DoS attack.
If A is false, then B must be true. If A is true, B can be either true or false.
So if you get a response within 5 seconds, you don't know if the service is under attack or not. Generally speaking, you can assume it's inclusive disjunction unless you're told it's the exclusive-or.