Logics for non monotonic reasoning

1. GANDHINAGAR INSTITUTE OF TECHNOLGY
Department of Information Technology
Logics For Non-monotonic
Reasoning
Student Name(Enroll No): Shaishav Shah(170120116094)
Name of Faculty: Prof. Anirudhdha Nayak
AI(2180703)

2. Non-monotonic Reasoning
• A non-monotonic logic is a formal logic whose
consequence logic is not monotonic.
• Logic is non-monotonic if the truth of a
preposition may change when new information
(axioms) is added.
• Allows statement to be retracted.
• Used to formalize plausible (believable)
reasoning.

3. Example 1
– Birds typically fly. Tweety is a bird.
– Tweety (presumably) flies.
• Conclusion of non-monotonic argument may not
be correct.

4. Example 2
– If Tweety is a penguin, it is incorrect to conclude
that Tweety flies.
(incorrect because, in example 1, default rules when
case-specific information was not available.)
• All monotonic reasoning are concerned with
consistency.
• Inconsistency is resolved, by removing the
relevant conclusion(s) derived by the default rules,
as shown in the next example.

5. Example 3
• The truth value(true or false), of prepositions such
as “Tweety is a bird” accepts default that is
normally true, such as “Birds typically fly”.
– A conclusion is derived was “Tweety flies”.
• When an inconsistency is recognized, only the
truth value of the last type is changed.

6. Thank You