Re: Database design

From: Alexandr Savinov <spam_at_conceptoriented.com>
Date: Wed, 22 Feb 2006 10:49:12 +0100
Message-ID: <43fc33a1$1@news.fhg.de>

Mark Johnson schrieb:
> Alexandr Savinov <spam_at_conceptoriented.com> wrote:
>

>> JOG schrieb:
>>> Mark Johnson wrote:
>>>> "x" <x_at_not-exists.org> wrote:
>>>>> "Roy Hann" <specially_at_processed.almost.meat> wrote in message
>>>>> news:3--dnYnbkrrCfmTenZ2dnUVZ8qadnZ2d_at_pipex.net...
>>>>>> "x" <x_at_not-exists.org> wrote in message news:dtcjfn$f87$1_at_nntp.aioe.org...
>>>>> Well, the slippery part is not that amusing after a while.
>>>>>> I am more inclined to read it as just the usual witless gaff of noticing
>>>>>> that the bounding box of a printed representation of a table has length
>>>>>> width and leaping to the conclusion that a table is therefore
>>>>>> two-dimensional; planar: flat.
>>>> Then I certainly stand to be corrected. I thought the relation was
>>>> thought to be essentially an unordered set or list of entities, and
>>>> nothing more.

>>> A tuple does not equate to an entity, in fact far from it.

>> So what is then an entity?

>
> As I understood it, the entity is each row in a relation, each entity
> consisting of various attributes, which alternately are termed,
> tuples. And each entity is supposed to be of 'like kind'.
> Unfortunately, based on previous messages, no one really seems to know
> what that is, or whether such 'like kinds' are even important.

Is it really necessary for an entity to be inside a relation?

The question is actually deeper than it seems to be. It can be reformulated in more general form as follows: can things live in isolation outside an environment? If yes, then entities probably do not need your constraint. I would prefer a variant where entities do not need an environment (a relation) and can exist in isolation because it is simpler. However, I cannot believe that it is possible because I have never seen entities in isolation and hence I think it does not make sense.

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Received on Wed Feb 22 2006 - 03:49:12 CST