Explain: Approaches to knowledge representation.

Q. Explain: Approaches to knowledge representation.

Following approaches can be used for knowledge representation –
            1. Logical representation
            2. Production rule representation
            3. Semantic networks
            4. Frame representation

Logical representation:

• It is mostly concerned with truth of statements regarding the world.
• These statements are most generally represented using TRUE or FALSE statements.
• Logic is used to define ways to infer new sentences from existing ones.
• Several logics are widely used –

           1. Propositional logic: They make use of propositions which can be either true or false.

           2. First order predicate logic: They are much more expressive and make use of variables, constants, predicates, functions, and quantifiers, along with connectives.

           3. Higher order predicate logic.

           4. Fuzzy logic: They indicate the existence of in-between-ness or fuzziness in all logics.

           5. Other logic: Include multiple valued logic, modal logic, and temporal logic.

Production rule representation:

• It is one of the widest methods to represent knowledge.
• It is also known as IF-THEN rules.
• Some of its benefits are that it is modular and independent of each other.
• New rules may be added and old ones may be deleted.
• Production rules are simple but powerful forms of representing knowledge.
• They provide flexibility for combining procedural and declarative representations in a unified manner.

Semantic networks:

• They represent knowledge in the form of graphical networks.
• They are represented concisely by nodes and edges.
• A semantic network consists of NODES that are named and that represent concepts, and LABELLED LINKS, that represent relations b/w the concepts.
• Ex.

             Tom is a cat.
             Tom caught a fish.
             Tom is grey in color.
             Tom is owned by Sam.
             Tom is a mammal.
             Fish is an animal.
             Cats love milk.
             All mammals are animals.

Frame representation:

• Frames are mostly used when the task becomes quite complex, and needs more
• structured representation.
• Frames are record-like structures that consist of a collection of slots or attributes, and
• the corresponding slot values.
• These slots can be of any size and type.
• The slots have names and values too. These are called Facets.
• Facets can have names or numbers.
• Ex.:

             (Ram)

             (PROFESSION (VALUE professor))

             (AGE (VALUE 50))

             (WIFE (VALUE sita))

             (CHILDREN (VALUE luv kush))