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

In message <%EX5a.232$hl5.34162743_at_mantis.golden.net>, Bob Badour <bbadour_at_golden.net> writes
>"Bernard Peek" <bap_at_shrdlu.com> wrote in message
>news:ixbyZQwB3AW+EwXz_at_diamond9.demon.co.uk...
>> In message <7Ik5a.164$8e.17186852_at_mantis.golden.net>, Bob Badour
>> <bbadour_at_golden.net> writes
>>
>>
>> >It's interesting how you are trying to mischaracterize Date as using
>> >primitive technology. Multisets are demonstrably more primitive than
>> >relations--simply from the fact that they rely on physical location. You
>are
>> >the one promoting the use of "Roman numerals and shells".
>>
>> Multisets may rely on physical location, although that's a special case.
>
>That's a very remarkable statement. By what other means may users of a dbms
>using a multiset logical data model make use of duplicates?

Whatever works. What they need is a way to select one of the duplicates. What that is will depend on whatever other attributes the duplicates have. There is no inherent requirement for that to be physical location.

>
>
>> The general case is that they rely on information outside the database
>> to distinguish different items.
>
>Really? That's quite extraordinary. How does the dbms use this external
>information in its logical data model?

It's not in the logical data model. How can it use it? But if you accept multisets that isn't a problem.

>
>
>> If that happens to be physical location
>> then you can add the current latitude, longitude and altitude as a key.
>
>Are you being facetious?

That depends on whether you consider a reductio ad absurdam argument to be facetiousness.

>
>
>> There are some practical problems but in theory it's possible. In
>> practise if you need to distinguish two cans of tuna you create an
>> identity field, call it "Can Number" and print labels to stick on each
>> can.
>
>I've identified plenty of cans on shelves, but I've never seen a "Can
>Number". Where might I find one of those?

Probably in a relational database.

-- 
Bernard Peek
bap_at_shrdlu.com
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