Re: [ontolog-forum] Proceedings: "Database & Ontology" mini-series Sessi

[paola.dimaio@xxxxxxxxx]

Thanks John


I do not mean to insist on this lilliputian quibble but... 


 >   Given: Tweety, Polly, and Hooty are birds. Fred is bat.
 >          Tweety, Polly, and Hooty fly. Fred flies.
 >   Assume: Every bird flies.



could you explain how does the bat part of your statement end up in the assumption that every bird flies? or does the assumption completely ignores the fact that Fred is a bat. yet it flies?
if the assumption is based on taking into account both parts of the statement, then the assumption as stated above seems incomplete - 

this logic right?

not everything that flies is a bird, and not every bird flies

I ll make something up for the class

(feel free to ignore )

P

On 7/14/07, John F. Sowa <sowa@xxxxxxxxxxx> wrote:

Paola,

In my previous note, I forgot to answer the following question:

PDM> My assumption, following your example 2 would be:
> not only birds fly -  would I be right?

JFS> 2. Induction. Assume a general principle that subsumes many facts.
>
>   Given: Tweety, Polly, and Hooty are birds. Fred is bat.
>          Tweety, Polly, and Hooty fly. Fred flies.
>   Assume: Every bird flies.

PDM> NOT ONLY BIRDS FLY.

Yes, that is true.  But that is a separate observation.

The assumption made by induction is "Every bird flies."

The additional statement "Not only birds fly" follows
from two facts plus some background knowledge plus an
inference.  Following are the facts as given:

     Fred is a bat.  Fred flies.

The additional background knowledge, which was not stated
in the slide, is

     No bat is a bird.

From that statement and the preceding facts, one can infer
by deduction:

     Some things fly that are not birds.

Then it is possible to rephrase that conclusion as a qualifier
to the preceding:

     Every bird flies, but not only birds fly.

In short, you could add that statement, but it is derived
by a more complex series of steps.  For teaching purposes,
it might be better to show that in a separate slide.

(And, of course, the statement "Every bird flies" has to be
qualified when you consider penguins and kiwis.  You also have
to exclude injured birds, baby birds, sleeping birds, and
dead birds -- remember the dead parrot from Monty Python.)

John


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-- 
Paola Di Maio 
School of IT
www.mfu.ac.th
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