Produce a knowledge base in PROPOSITIONAL LOGIC capturing the following informat

Question

Produce a knowledge base in PROPOSITIONAL LOGIC capturing
the following information as closely as possible as stated here: If Tweety is
a bird and it is not an abnormal bird, then it
fies. A bird is abnormal
exactly when it is an ostrich, a penguin, or not an abnormal wooden bird. A
wooden bird is abnormal exactly when operated under remote control. Tweety
is a bird, it is not an ostrich nor a penguin nor a remote controlled wooden
bird. Prove using Prover9 that Tweety
fies. Notice that the two forms of
abnormality mentioned here may be different, one is if birds, the other is for
wooden birds

Explanation / Answer

The sentence "Birds fly" is not synonymous with "All birds fly" because there are exceptions. In fact, there are overwhelmingly manyexceptions--ostriches, penguins, Peking ducks, tar-coated birds,
fledglings, etc. etc.--a seeminglyopen-ended list. Nevertheless, if told only about a particular bird, say Tweety, without being told anything else about it, we wouldbe justified in assumingthat Tweetycan fly, without knowing that it is not one of the exceptional birds. In other words, we treat Tweety
as a typical or normalbird. Wecan represent the sentence "Birds fly" by instances of our patterns
of plausible reasoning: "Normal, birds fly." "Typically, birds fly." "It x is a bird, then assumeby default that x flies."

In the theory of databases there is an explicit convention about the rep-resentation of negative information that appeals to a particular kind of default assumption. the following "necessary conditions" for the concept "bird":
If BIRD(x) then VERTEBRATE(x).
If BIRD(x) then normally FLY(x).
If BIRD(x) then assume by default BIPED(x).
If BIRD(x) then typically FEATHERED(x).
If BIRD(x) then typically HAS-AS-PART(x,beak(x)). etc.

The bird concept also possesses "sufficient conditions," someof which are logical implications while others fit our pattern for default reasoning:
If SPARROW(x) then BIRD(x).
If FLY(x) & CHIRP(x) then assume by default that BIRD(x).
If FLY(x) & FEATHERED(x) then assume by default that BIRD(x). etc.

if CHIRP(x) and FLY(x) then assume by default BIRD(x).

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