Correct Subject : use of multiple and sufficient blocks

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Correct Subject : use of multiple and sufficient blocks

Alan March
Sorry for reposting, but I used the wrong title

Hi.

Sometime ago I posted a message inquiring as to the intended use of multiple
Necessary and Sufficient blocks. I did receive some answers, but they were
mostly examples, and did not quite answer my question.

So again, when should multiple N&S blocks be used? As far as I have
reasoned, they should be used when different groups of axioms, each of them
by themselves or together, allow for a complete definition of a class.
Horridge et al's Owl Tutorial carries an example of *how* to establish
multiple N&S blocks, but, at least to the best of my undestanding, not
*when* to use them. As far as I can gather, it would seem that they must be
used in the manner I explained above. Thus, an individual may be considered
a member of the "triangle" class when it *either* "has three angles and is a
subclass of shape" **or** "has three sides and is a subclass of shape", or
*both*. When I emphasize "both", I mean to say that if such individual
fullfilled both N&S blocks, it would also be a member of the triangle class.
So, my conclusion is that multiple N&S blocks would seem to boil down to a
sort of "and/or" situation, where a class may be defined as such if it
carries either block or both blocks. Am I right in this assumption?

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Re: Correct Subject : use of multiple and sufficient blocks

Timothy Redmond

> So, my conclusion is that multiple N&S blocks would seem to boil down to a
> sort of "and/or" situation, where a class may be defined as such if it
> carries either block or both blocks. Am I right in this assumption?
This isn't right.  Multiple N&S blocks are used when you have more than
one definition for a single concept.  So you could have two definitions
for a triangle:

    Triangle = (Polygon & (hasVertex = 3))
    Triangle = (Polygon & (hasEdge = 3))

This is a slightly contrived example but  you can see that the intent is
that both definitions define the same thing.  If an individual satisfies
the criteria of the first definition then he will also satisfy the
criteria of the second definition and vice versa.

As to the question of when this is the best way to model something I  
will leave that to others to answer.


-Timothy

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