# Rules of Inferences

• May 16th 2009, 10:53 PM
billyso23
Rules of Inferences
Find the relevant conclusion or conclusions from the given set of premises.

"If I take the day off, it either rains or snows."
"I took Tuesday off or I took Thursday off."
"It was sunny on Tuesday."
"It did not snow on Thursday."

The problem that I have with this question is setting up the premises. I do have the answer and I don't understand it. The thing that confuses me is the date.

Do I set the date in with the premise as one proposition or two propositions. To me, both are necessary.
ie The 2nd premise and the last one respectively.

Thanks
• May 17th 2009, 07:39 AM
TiRune
Kinda depends on the logic you are allowed to use, but in general:

NOT weather(snow, Thursday)
weather(sunny, Tuesday)
take_day_off(Tuesday) XOR take_day_off(Thursday)
take_day_off(x) IMPLIES (weather(rain, x) XOR (weather(snow,x))

try and find the missing information now, we know the weather on both days, s we need to know if the day was taken off on Thursday or Tuesday.

if Tuesday was taken off, this would mean that (weather(rain, x) XOR (weather(snow,x)) is true, which it is not since weather(sunny, Tuesday). So take_day_off(Tuesday) is false.
take_day_off(Tuesday) XOR take_day_off(Thursday) now says that take_day_off(Thursday) is true. a combination of NOT weather(snow, Thursday) and take_day_off(x) IMPLIES (weather(rain, x) XOR (weather(snow,x)) now says that the weather on Thursday was rain.

Sorry for the crappy notation, forgot how to make the logical symbols on here...
• May 17th 2009, 11:31 AM
billyso23
TiRune

Your answers are right, and I will work on the question using your suggestion.

Thanks