Lecture - 9 First Order Logic

[hac1m]

his handwriting is sooooooo good

[potatoqueue]

I don't really think Russell's paradox is actually a paradox because of the fact that there's no constraint that says only a barber can shave someone.

[blablabla1000able]

this is AWESOME, thank you

[subhanice]

ya thanks to the prof so nice of u people to uplaod it i was struggling with it since morning and now i know fol :)

[michaelkarpeles]

I apologize, but there is indeed an error in the example. Please see my follow up post as a case is provided.

For the English sentence: "Not all students take both History & Biology",

The FOL solution sentence: ~[Vx Student(x) => Takes(History, x) ^ Takes(Biology,x)] is incorrect.

The correct solution (which is not logically equivalent) is:

Ex Student(x) => ~Taking(Biology, x) v ~Taking(History, x)

Explanation: 2 students in KB. 1 takes 0 classes. 1 takes both bio and history. Conflict.

[michaelkarpeles]

@michaelkarpeles

Case: Assume KB of students s1 takes no classes and s2 takes both biology and history. Thus s1 results in FALSE for Student(x) => Takes(History, x) ^ Takes(Biology,x) and becomes TRUE once the Universal quantifier is negated. However, s2 results in Student(x) => Takes(History, x) ^ Takes(Biology,x) evaluating to TRUE, thus becoming FALSE after negation. This sentence thus results in FALSE when it is obviously TRUE that in our KB, not all students take both History & Biology.

[AJSwisgirl]

@michaelkarpeles I think you're confused, what Prof. wrote is correct. "All student x implies takes history x and biology x ,, negating all sentence will read Not all student..........,.,.,., what ur trying to say is beyond me.

he's not talking 2 students in here or saying s1 or s2 ? there are no information that s1 takes no classes. And sentence doesn't start with there exist... and connective is ^ (and) not V (or).

[warhols25]

Illuminating ! YouTube is the future of the world !

[marceloarraeste]

@warhols25 Illuminating ! YouTube is the future of the world ! [2]

[nonamesaved]

Professor realy saved me today!!! A million thanx is not enough

[suryabhan8777]

Thanks Sir this is very helpful lecture.

[bhavanisetty]

thanks for posting this video

[MWatkins1411917]

Interesting...

[bandinopla]

in a primary school what you say is more probable... but in a university class i dont think that no one get the highest score... thats whould be weird

[bandinopla]

hemmm.... i'm from argentine, i speak spanish and i learned english watching movies and i can undestand pretty well what Prof. Dasgupta is saying... so mabe is you ?

[DepecheMol]

@bandinopla I'm from ARGENTINA, and didn't miss a single word.. keep working on that mate.

[cumsh00ter]

you talking out of your asshole this guys english is perfectly ok for what he is teaching i would understand your frustration if he was teaching english but he isnt, so be grateful phukk head!.

[teejayandrade]

mate u hear another language other than english being spoken ??

[Theraot]

Wrong. Example 4 is wrong because the expression proposed as solution will be true when: all the students scored more in History than in Bio. Even if that warranties that when the given expression is true, the best score of History is greater than the best of Bio; there exist the case is which an student that taken History has less score than some other student that taken Bio (making the said expression to be false), and still the best score of History may be greater than the best score of Bio.

[asharma78901]

Its not wrong...

Reading it out in English, it sounds something like:

For all the students that take Bio, there exists a student of history, and that student of history scores higher.

So only one student of history has to score higher then all the students of bio.

really, its: a score in History (doesnt have to be the best) > the best (all) scores in bio

so you can deduce that the best score of history is indeed higher than the best score of bio.

P.S. - Thanks for Uploading the videos

[michaelkarpeles]

@asharma78901

This is actually incorrect. The first order logic sentence may seem to read like the English sentence, but they are not equivalent. Please refer to my other post which illustrates a case wherein this logical solution does not hold for a legal knowledge base.

Best wishes

- Mek

[AJSwisgirl]

@michaelkarpeles He is answering your confusion in second bit in the example. There exists student x and doesn't take history x or bilogy x that is as you mentioned s1 doesn't take neither of them. You confused me too

:-)) Your explanation hard to understand.

[eatme690808]

@asharma78901 Thanks for the clear explanation! For anyone else confused, another way to look at is that for ANY score in Bio, you can always find someone with a higher score in History.