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

From: Steve Kass <skass_at_drew.edu>
Date: Mon, 24 Feb 2003 10:57:10 -0500
Message-ID: <b3dfa7$lnq$1@slb5.atl.mindspring.net>


Lauri,

  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 ζ˜ŸζœŸδΈ€ 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.

SK

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!
>
>see http://www.pgro.uk7.net/x_duplicates.htm
>
>regards,
>Lauri Pietarinen
>
>
Received on Mon Feb 24 2003 - 09:57:10 CST

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