Q.2. Explain the various problems in representing knowledge.
Ans. The major problem in representing knowledge is the problem of representing the facts that change as well as that do not.
This is known as frame problem In some domains, the only hard part is representing all the facts. In others, though, figuring out which ones change is non-trivial.
Also there are several limitations of logic as a knowledge representation scheme .
(i) Logic and theorem proving technique are monotonic in nature. The derived axioms hold good under all circumstances. Real world is never monotonic for information obtained is seldom complete.
(ii) Logic does not provide facilities for handling uncertainty. Every information it deals has to be either correct or incorrect but never partially.
(iii) Codification of the problem in logic is a tough task and required considerable effort on the part of the user.
(iv) Even though various techniques do exist for speeding resolution. it takes considerable amount of time to prove statements in logic.-
(v) One major constraint in logic is that unless you are sure that a solution exists. the search will not terminate. We will be going on adding clause after clause but the solution will be still elusive.
(vi) Heuristics, which form the private knowledge of the experts are difficult to be codified in logic.
Marcus was a man — man (Marcus)
The representation captures the critical fact of Marcus being a man, but if fails to capture some of the information in the English sentence, namely the notion of past tense.