The two quantifiers are the existential quantifier, which is denoted ∃ and is pronounced as “there exists”, and the universal quantifier, which is denoted ∀ and is pronounced as “for all”.

Examples: a restaurant that serves Mexican food near ICSI.

∃xRestaurant(x) ∧ Serves(x,MexicanFood) ∧ Near( (LocationOf(x),LocationOf(ICSI) )

All vegetarian restaurants serve vegetarian food.

∀xVegetarianRestaurant(x) =⇒ Serves(x,VegetarianFood)



Variables and Quantifiers

University of Michigan - Ann Arbor

First-Order Logic (FOL) is a flexible, well-understood, and computationally tractable meaning representation language. It provides a sound computational basis for the verifiability, inference, and expressiveness requirements, as well as a sound model-theoretic semantics.

First-Order Logic

An on-going but a helpful book resource about NLP
https://web.stanford.edu/~jurafsky/slp3/

Speech and Language Processing (3rd ed. draft) 

Inference adds valid new propositions to a knowledge base or determines the truth of propositions not explicitly contained within a knowledge base.

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