Re: Guessing?
From: paul c <toledobysea_at_ac.ooyah>
Date: Tue, 27 May 2008 13:59:38 GMT
Message-ID: <etU_j.167881$rd2.59570_at_pd7urf3no>
>
> This just does not make sense. Suppose that a Vendor can also be a Customer
> since they're both Companies, and suppose that Company 'Philco' usually
> supplies 'RG6 connectors,' but occasionally buys them. So then if you have
> two relations,
>
> VendorParts {Company, Part},
>
> CustomerParts {Company, Part},
>
> that enumerate the parts that a company supplies and the parts that a
> company buys respectively,
>
> the tuple, {Company:'Philco', Part:'RG6 connector'}, can obviously appear in
> both relations, so I don't buy the notion 'any tuple satisfies the predicate
> of at most one relation.'
> ...
Date: Tue, 27 May 2008 13:59:38 GMT
Message-ID: <etU_j.167881$rd2.59570_at_pd7urf3no>
Brian Selzer wrote:
> "Bob Badour" <bbadour_at_pei.sympatico.ca> wrote in message
> news:483ac46d$0$4069$9a566e8b_at_news.aliant.net...
>> paul c wrote: >>> Bob Badour wrote: >>> ... >>> >>>> ... (Not that I like anthropomorphizing dbmses.) >>> Right, saying the dbms 'knows' something invites talk of it being able to >>> 'guess' and other mysticisms. For want of a better word, for now I'll >>> try to remember to quote it. >> With POOD, any tuple satisfies the predicate of at most one relation in >> the dbms. Thus, with POOD, the dbms can calculate a unique relation to >> which to apply any insert, update or delete with the goal of avoiding >> anomalous behaviour. >>
>
> This just does not make sense. Suppose that a Vendor can also be a Customer
> since they're both Companies, and suppose that Company 'Philco' usually
> supplies 'RG6 connectors,' but occasionally buys them. So then if you have
> two relations,
>
> VendorParts {Company, Part},
>
> CustomerParts {Company, Part},
>
> that enumerate the parts that a company supplies and the parts that a
> company buys respectively,
>
> the tuple, {Company:'Philco', Part:'RG6 connector'}, can obviously appear in
> both relations, so I don't buy the notion 'any tuple satisfies the predicate
> of at most one relation.'
> ...
Isn't this a straw man too? (arguing against POOD with an example that doesn't follow POOD.) Received on Tue May 27 2008 - 15:59:38 CEST