some semantic puzzles from VOEvent

[Bernard Vatant]

Rob

> > nobody has found so far a consensual definition of what an human *is*.
>
> Actually, we have an excellent operational definition of "human" (in
> its meaning as a synonym for Homo sapiens).  A human is an
> interbreeding (hypothetically or actually) descendent of humans.
> Combine that rule with an example entity deemed to be human and stir
> inductively.

Cool. I love recursive definitions :)
That one is certainly operational - fit for everyday life affairs. But to provide a
scientific definition of human kind as a species, forget it, it's easily broken ...
1. Species historical limits : If every human is a descendent of humans, recursively, hmm,
I would be happy to trace my ancestors back to, say, 200 millions years ago, and meet them
one by one - just to check the humanity breaking point ... Not to mention my descendents
200 millions years from now ... if any ...
Seriously, there is a fuzzy border somewhere. "When in Earth history did humanity begin?"
is a question exactly similar to : "When in Universe history did galaxies appear"?
2. For each individual : When do I start/end my story as an human? Think about difficult
and endless debates about abortion and euthanasia. As difficult as : When does the Sun
starts/ends as a star ... No more, no less ... And not to mention monsters of all kinds,
that make wonder about limits of humanity ...

And this goes along the lines of the point you made a few messages up in this thread :
interesting science happens on the borders of agreed upon ontology. Is this a star or not?
Is this an human or not? even in "pure" maths : Is this a line? Is this a number? Is this
a function? Such questions led to the most important advances in every domain of science.

> The point here is that evolution serves as a unifying
> force in constructing biological ontologies.

Well, evolution gives a framework for biological taxonomy construction, yes ... but
nevertheless ... the differentiation breaking point of a species is still something very
difficult to define, and hard to observe. I won't elaborate on the details here, but I had
an interesting breakfast with a botanist a while ago, which definitely destroyed in my
mind the notion of any "objective" definition of what a species is ...

> Astronomy has no similar unifying conceptual framework
> above the level of fundamental physics.

True, maybe, but such "unifying conceptual framework" would not solve the above issues,
more than evolution did in Biology.

> > even more simple questions are tricky : what is the minimal size
> > for a planet? for an asteroid? for a comet? Every value would be
> > arbitrary, although nobody I guess would call a body of mass a few
> > grams orbiting the Sun a planet ... All those issues boil down to
> > the good old undecidable question "What is the minimal number of
> > grains to make a sandheap?"
>
> Yes, but I question your assertion that these questions are
> undecidable.

"Undecidable" was not adequate a word, I agree, if you read it in its strict logical
sense. I mean you can chose any arbitrary limit, like geographs do for the classification
of cities, by setting arbitrary population thresholds ...

> The literature is rife with variations on ways to
> express size distributions (e.g., initial mass functions) that would
> allow capturing such subtleties.  Does "natural language" include the
> mathematical expressions that are the natural way to express so many
> astronomical concepts?

Depends on what you call "natural language". Not sure if it contains any mathematical
expressions at all ...

> Does knowledge engineering extend to actually
> expressing an HR diagram - or would Ejnar and Henry simply have to
> describe the main sequence in prose - or perhaps poetry?  "I think I
> shall never see, a poem as lovely as the asymptotic giant branch."

This is an interesting challenge indeed ...

Bernard

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Bernard Vatant
Senior Consultant
Knowledge Engineering
bernard.vatant at mondeca.com

"Making Sense of Content" :  http://www.mondeca.com
"Everything is a Subject" :  http://universimmedia.blogspot.com

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