Important Questions and Answers: Artificial Intelligence Planning

1. What are the standard quantifiers of First Order Logic?

The First Order Logic contains two standard quantifiers.

They are:

i)                                           Universal Quantifiers

ii)                                        Existential Quantifiers

2. Define Universal Quantifier with an example.

To represent “All elephants are mammal” “Raj is an elephant” is represented by Elephant (Raj) and “Raj is a mammal”. The first order logic is given by

Elephant (Raj) => Mammal (Raj)

Elephant (John) => Mammal (John)

Thus it is true if and only if, all the above sentences are true that is if p is true for all objects x in the universe. Hence, is called universal quantifier.

3. Define Existential Quantifier with an example.

Universal quantification makes statements about every object. Similarly, We can make statement about some object in the universe without naming it, by using an existential quantifier.

To say, for example, that king john has a crown on his head, we write

x is pronounced “There exists an x such that…..” or “For some x…”

The sentence says that P is true for at least one object x. Hence, is called existential quantifier.

6. What is the use of equality symbol?

The equality symbol is used to make the statements more effective that two terms refer to the same object.

Eg: Father (John) = Henry

7. Define Higher Order Logic.

The Higher Order Logic allows quantifying over relations and functions as well as over objects.

Eg: The two objects are equal if and only if, all the properties to them are equivalent.

8. Define First Order Logic.

First Order Logic, a representation language that is far more powerful than propositional logic. First Order Logic commits to the existence of objects and relations.

Eg: One plus two equals three

Objects                - one, two & three

Relations - equals

Functions - plus

9. What is called declarative approach?

The representation language makes it easy to express the knowledge in the form of sentences. This simplifies the construction problem enormously. This is called as declarative approach.

10. State the aspects of a knowledge representation language.

A knowledge representation language is defined in two aspects:

i) Syntax: The syntax of a language describes the possible configuration that can constitute sentences.

ii) Semantics: It determines the facts in the world to which the sentences refer.

11. What is called entailment?

The generations of new sentences that are necessarily true given the old sentences are true. This relation between sentences is called entailment.

12. What is meant by tuple? 

A tuple is a collection of objects arranged in a fixed order and is written with angle brackets surrounding the objects.

{< Richard the Lionheart, King John>, <King John, Richard the Lion heart>}

13. What is Propositional Logic?

Propositional Logic is a declarative language because its semantics is based on a truth relation between sentences and possible worlds. It also has sufficient expressive power to deal with partial information, using disjunction and negation.

14. What is compositionality in propositional logic?

Propositional Logic has a third property that is desirable in representation

languages, namely compositionality. In a compositionality language, the meaning of sentences is a function of the meaning of its parts. For example, “S1 ^ S2” is related to the meanings of “S1 and S2”.

15. Define Symbols.

The basic syntactic elements of first order logic are the symbols that stand for objects, relations and functions. The symbols are in three kinds. Constant symbols which stand for objects, Predicate symbols which stand for relations and Function symbol which stand for functions.

16. Define ground term, Inference.

The term without variables is called ground term.

The task of deriving the new sentence from the old is called Inference.

17. Define Datalog.

The set of first order definite clauses with no function symbols is called

datalog.

Eg: “The country Nono, an enemy of America”

Enemy(Nono, America)

The absence of function symbols makes inference much easier.

18. What is Pattern Matching?

The “inner loop” of the algorithm involves finding all possible unifiers such that the premise of a rule unifies with a suitable set of facts in the knowledge base. This is called Pattern Matching.

19. What is Data complexity?

The complexity of inference as a function of the number of ground facts in the database is called data complexity.

20. Define Prolog.

Prolog programs are sets of definite clauses written in a notation somewhat different from standard first-order logic.

21. What are the principal sources of Parallelism?

The first called OR-Parallelism comes from the possibility of a goal unifying with many different clauses in the knowledge base. Each gives rise to an independent branch in the search space that can lead to a potential solution and branches can be solved in parallel.

The second called AND-Parallelism comes from the possibility of solving each conjunct in the body of an implication in parallel.

22. Define conjunctive normal form. 

First Order resolution requires that sentences be in conjunctive normal form that is, a conjunction of clauses, where each clause is a disjunction of literals. Literals can contain variables, which are assumed to universally quantified.

For ex, the sentence

23. Define Skolemization. 

Skolemization is the process of removing existential quantifiers by elimination.

24. What is the other way to deal with equality?

Another way to deal with an additional inference rule is

·                                                                    Demodulation

·                                                                    Para modulation

25.            Define the ontology of situation calculus.

Situations, which denote the states resulting from executing actions. This approach is called Situation Calculus.

·                                            Situations are logical terms consisting of the initial situation and all situations that are generated by applying an action to a situation.

·                                            Fluent are functions and predicates that vary from one situation to the next, such as the location of the agent.

·                                            Atemporal or eternal predicates and functions are also allowed.