Re: Database design

Alexandr Savinov <spam_at_conceptoriented.com> wrote:

>I am afraid that both terms (entity and tuple) have wider scope than
>entity-relational model and normal forms. And this is precisely why it
>is interestingly to compare them. In particular, (if you insist that
>they are different things) why entity is NOT a tuple and vice versa why
>tuple is NOT an entity? Of course, we might add to this comparison list
>some other terms like object, row, record etc. But since we cannot even
>formulate the difference between the above two terms I think adding more
>complexity does not make sense.

It's merely definition, and some here insisting that one framework never apply, or another. So if one consistently referred to "instances" instead of entries or entities, that would be ruled out of hand. Yet a tuple can be said to be an instance, particularly if one is consistent in applying other OO terminology, like class, method, reference, etc.

>define terms indefinitely - you must stop somewhere. So it is not a
>solution. Such terms as the above two are precisely a kind of such terms
>that are very difficult to define. We can only characterize them in
>great extent informally.

Well, within a context or framework of ER it might be possible to speak of entities, and specific entities, identifiers, and under the framework of Codd perhaps speak of relations, tuples, and PK. Various terms can apply to the same thing, in different contexts. Call it - alternate naming conventions, perhaps?

>You can also define a structure as deep. For example, if it is
>equivalent to a hierarchical space. It is also not excluded that some
>other term could be helpful such as fat, thin etc. Notice that these
>terms are far from the most exotic ones in science. (Fuzziness and
>roughness of sets, charmness of quarks etc.)

Flat in the context of a heirarchy. If a relation is simply an unordered list, sorted or not, it is flat. But it's a very informal and loose characterization, which seems to have rubbed some the wrong way; perhaps sparking, in a fuzzy and weakly vague fashion, an objection to those who would somehow wish to call multi-dimensions, or a Cartesian product, flat. But I don't know. Received on Wed Feb 22 2006 - 11:52:45 CET