Question

Explain the following terms in expert systems:

Hypothetical Reasoning, Predicate Calculus and Blind Search

Answer 1

Hypothetical Reasoning

In the development of advanced knowledge based systems a hypothetical reasoning system is an important framework. It can be applied to many practical problems including model based diagnosis. In prolog based implementation the interference speed is slow. This is because of inefficient backtracking. In order to overcome this problem, a fast hypothetical reasoning mechanism for propositional-logic knowlegde has been developed. It is developed by combinig the advantage of forward and backward reasoning styles.

Predicate Calculus

  Predicate calculus, or predicate logic, is a kind of mathematical logic, which was developed to provide a logical foundation for mathematics, but has been used for inference in other domains.

In predicate logic, the simplest wff consists of a predicate followed by one or more arguments : P(a₁, a₂, ..., a_n). Each argument represents an individual object in the domain under discussion, and each predicate represents an attribute or a relation in the domain. For each predicate, the number of arguments and their order are determined. That is, if both P(a) and P(a, b) are wffs, then the two Ps are different predicates. In general, P(a, b) and P(b, a) may have difference in meaning and truth value.

Blind Search

A blind search (also called an uninformed search) is a search that has no information about its domain. The only thing that a blind search can do is distinguish a non-goal state from a goal state. A blind search will have no preference as to which node it should explore first.

Uninformed search methods:

1. Breadth-first search

2.  Uniform-cost search

3. Depth-first search

4. Depth-limited search

5.Iterative deepening search