Re: Extending my question. Was: The relational model and relational

From: Steve Kass <>
Date: Mon, 24 Feb 2003 10:57:10 -0500
Message-ID: <b3dfa7$lnq$>


  Date's argument is this:

  What does AS mean by "a penny"? Suppose I give him
  two pennies but assert I am giving him just one. How does
  he know I am wrong? The answer has to be: by counting!
  Thus, I submit that he has to be able count pennies in order
  to be able to execute the first step of his algorithm

Date is saying that multisets are invalid because they
can't determine whether or not he is lying about what a
penny is.  If that is a requirement, then I fully agree that
multisets don't meet that requirement.  If at some point I
need to design a database with such characteristics, I'll
use a more suitable model.

If Date gives AS two pennies, asserting that it is one,
AS should first ask Date whether he has a question
or is perhaps just trying to buy two cents worth of
information (assuming Date equates penny with cent).

If Date does ask how many pennies there are, AS
should use Date's definition of a penny.  If the database
is currently in a state representing a multiset of 71 pennies,
AS should report back to date that there are 35.5 pennies.
No one is wrong.  In many cases databases provide
contextual answers.  Many a database will report today's
day of the week as Monday to an New Yorker, as lundi
to a Parisian, and as 星期一 to a resident of Beijing.  There's
no reason the database can't report a numerical quantity
in units, pairs, dozens or gross as well, on demand.


Lauri Pietarinen wrote:
All I need is to distinquish -- rather than count -- one can, then
make the assumption that this separate entity has "the weight of one
can" and that all cans in the bag have the same weight  -- basically,
the inductive hypothesis, but for unordered collections.  Distinction
is a more primitive operator than counting.

I think Date has a valid point in that in order to weigh one
can you _have_ to be able to count it!


Lauri Pietarinen
Received on Mon Feb 24 2003 - 16:57:10 CET

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