check yourself-III with answers

1)Discuss First order logic with example?

First-order logic is symbolized reasoning in which each sentence, or statement, is broken down into a subject and a predicate. The predicate modifies or defines the properties of the subject. 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. In first-order logic, a sentence can be structured using the universal quantifier (symbolized ) or the existential quantifier

2)Define semantic network?

A semantic network, or frame network, is a network that represents semantic relations between concepts. This is often used as a form of knowledge representation. It is a directed or undirected graph consisting of vertices, which represent concepts, and edges.

3)Define Horn clause?

A Horn clause is a clause with at most one positive literal.
Any Horn clause therefore belongs to one of four categories:

A rule: 1 positive literal, at least 1 negative literal

A fact or unit: 1 positive literal, 0 negative literals.

A negated goal : 0 positive literals, at least 1 negative literal.

The null clause: 0 positive and 0 negative literals. Appears only as the end of a resolution proof.

4)Analyse clausal form and its usefulness

To demonstrate that assumptions imply a conclusion, it is helpful to construct a proof consisting of inference steps. For the proof to be convincing, the steps need to be direct and obvious, so the sentences should be unambiguous and their grammar should be as simple as possible.

The clausal form of logic fits this simplicity requirement. Its simplest sentences are atomic sentences, which name relationships between individuals:

likes(sweetie, rover)
it_is_raining.
gives(eve, adam, apple).

 5)Explain some knowledge representation techniques?

●     There are different ways of representing knowledge e.g.

predicate logic,

semantic networks,

extended semantic net,

frames,

      conceptual dependency

6)Differentiate propositional and First order logic.

Propositional logic is declarative.

It allows partial/disjunctive/negative information.

Propositional logic has very limited expressive power.

FOL

It deals with object,relation and function.

It uses connectives

The FOL has more expressive power.

7)Compose the meaning of resolution/Refutation

Resolution yields a complete inference algorithm when coupled with any complete search algorithm.Resolution makes use of the inference rules.Resolution performs deductive inference.Resolution uses proof by contradiction. One can perform Resolution from a Knowledge Base. A Knowledge Base is a collection of facts or one can even

call it a database with all facts.

8)How predicate logic is helpful in knowledge representation?

predicate logic, involves using standard forms of logical symbolism which have been familiar to philosophers and mathematicians for many decades. Most simple sentences, for example, ``Peter is generous'' or ``Jane gives a painting to Sam,'' can be represented in terms of logical formulae in which a predicate is applied to one or more arguments

9)Compose a well formed formula?

Not all strings can represent propositions of the predicate logic. Those which produce a proposition when their symbols are interpreted must follow the rules given below, and they are called wffs(well-formed formulas) of the first order predicate logic.