Algoritmes Lecture 1 Flashcards
Propositional Logic
Logic-based onto statement(proposition) about the world
Propositional symbols
P Q R
representing a fact about the world
or idea
Sentence
an assertion about the world
Logical Connectives
not, and ^, or v, implication->, biconditional
Inference
a conclusion reached on the basis of evidence and reasoning. In this case, based on the data the computer has.
Knowledge Engineering
the branch of artificial intelligence concerned with building knowledge-based systems.
Inference Rules
Having new data out of existing. If Alpha -> B and Alpha is true then B is also true.
Inference by Resolution
The resolution inference rule takes two premises in the form of clauses (A ∨ x) and (B ∨ ¬x) and gives the clause (A ∨ B) as a conclusion. The two premises are said to be resolved and the variable x is said to be resolved away. Resolving the two clauses x and x gives the empty clause.
First-Order Logic
Constant symbol: Harry, Gryffindor
Predicate symbol: Person, house, belongs to
Can be true for Harry but false for Gryffindor
In first-order logic, a predicate can only refer to a single subject. First-order logic is also known as first-order predicate calculus or first-order functional calculus. A sentence in first-order logic is written in the form Px or P(x), where P is the predicate and x is the subject, represented as a variable.
Extention Qualification
An existential statement is a statement that is true if there is at least one variable within the variable’s domain for which the statement is true.
One thing true for all variables
Universal Qualification
A universal statement is a statement that is true if, and only if, it is true for every predicate variable within a given domain.
Something true for all variables
∀
This symbol means for all
