Re: Less strong equivalences

On Mar 26, 2009, at 10:58 AM, Phillip Lord wrote:

> Pat Hayes <phayes@ihmc.us> writes:
>>> We can consider this as
>>> problematic even with a very simple example.
>>>
>>> Let's assume we have two databases with information about Carbon.
>>
>> meaning, I presume, the element with atomic number 14.
>
> I was thinking of the carbon with atomic number 6.

Sorry, wrong terminology. My bad. But its the element we are talking  
about, is the point.

>
>
>
>>> Maybe,
>>> but what happens if one is talking about the structure of Carbon and
>>> it's location in the periodic table, while the other is talking  
>>> about
>>> Carbon with the isotopic mix that we have in living organisms on  
>>> earth?
>>
>> So what? They can be saying different things about the same  
>> element. Any
>> isotopic mix of carbon is still carbon.
>
> Different isotopic mixes have different properties. Atomic masses,
> melting points and so on.

Right. But they can still be mixes of the same element. We are talking  
about two different things: elements, and particular isotopic mixes.  
They have different identity criteria and different properties;  and  
they are closely related, but not identical to one another. This is  
really just an example of the solution to the vague-sameAs issue in an  
earlier email. In order to treat different isotopes as 'identical', we  
invent a (slightly) more general concept, called in this case an  
'element', map the isotopes to that, and use (actual) identity on the  
elements rather than the isotopes. This isnt historically accurate, of  
course, but its the same logic at work.

>
>
>>> In biology, we have the same problem. Is porcine insulin the same as
>>> human insulin? Is "real" human insulin the same as recombinant
>>> human insulin? Well, the answer to all of these is no
>>
>> Fine, you just answered the basic ontological question.
>>
>>> , even though most
>>> biologists will tell you that real and recombinant insulin are the  
>>> same
>>> because they have the same primary sequence; a medic will tell you
>>> otherwise, because they have different effects. Why? Don't know.
>>
>> A deep question, but not a killer for ontology use.
>
>
> It's not a deep question, just one to which we don't have an answer.
>
>
>
>>> If you make the distinctions that you might need some of the time,  
>>> all
>>> of the time, then you are going to end up with a very complicated  
>>> model.
>>
>> Yes, you no doubt are. Tough. Its a complicated world.
>
> Yes. And on of those complications is that we have to engineer for
> usability as well as accuracy.

In my experience, they often go together. Inaccuracy makes things seem  
easier to use at first, but they rapidly break, giving rise to a lot  
more work than if one had done it right in the first place.

>
>
>
>> Formal ontologies are
>> often, perhaps always, more complicated than the  informal  
>> 'knowledge' they
>> set out to formalize. They are obliged to  make finer, more  
>> persnickety,
>> distinctions between things.
>>
>>> Hence the evolutionary biologist says all the insulins are the same.
>>
>> I don't care what the anyone says, that is wrong. They are  
>> indistinguishable
>> for certain purposes, but if anyone can distinguish  them at all,  
>> they are not
>> the _same_.
>
> I think that position is defensible, but unusable.

Sorry, this particular point is not open for negotiation. That  
distinguishable things are not identical is a necessary, logical  
truth. If you want to deny this, I have no idea what you are saying.  
You aren't talking English.

>
>
>> All these examples can be handled by making fussy distinctions  
>> between kinds
>> of thing at different granularities: carbon molecules, carbon   
>> isotopes,
>> carbon the element; and then having mappings between them.   I  
>> don't know much
>> about insulin, but it sounds from the above that the  same trick  
>> would work.
>> It is tedious and hair-splitting to set this  up, but once in place  
>> its fairly
>> easy to use: you just choose the  terminology corresponding to the  
>> 'level' you
>> wish to be talk ing  about. sameAs works OK at each level, but you  
>> can't be
>> careless in  using it across levels.
>>
>> If this makes you want to groan, I'm sorry. But ontology  
>> engineering is rather
>> like programming.
>
> Actually, I quite like programming. I also know how to split things  
> out
> in the way you describe.
>
>
>> It requires an unusual attention to detail and a willingness to write
>> a lot of boring stuff, because its for computers to use, and they are
>> as dumb as dirt and have to have every little thing explained to them
>> carefully. And yup, its complicated. Until AI succeeds, it will  
>> always
>> be complicated.
>
> I'd quite enjoy it if you could patronise me a little more please.

Well, sorry, but (1) this is for public consumption so we expect a  
little rhetoric, and (2) you are the one who seems to be wanting a  
magic bullet.

>
>
>>> The only solution (which is too complicated) I can
>>> think of is to do what we do when we have this problem in  
>>> programming;
>>> you use a pluggable notion of equality, by using some sort of  
>>> comparitor
>>> function or object. I don't think that this is an issue for OWL  
>>> myself;
>>> I think it's something we may need to build on top of OWL.
>>
>> It belongs in your ontology for carbon and insulin, not in OWL.
>
> Is that not what my last sentance says?

Yes, I was intending to express agreement with you here.

Pat

>
> Phil
>
>

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Received on Thursday, 26 March 2009 17:57:24 UTC