Re: The Theoretical Foundations of the Relational Model

In article <3d18aabe.12240781_at_news.verizon.net>, JRStern <JXSternChangeX2R_at_gte.net> wrote:
>On 25 Jun 2002 11:51:29 +0200, hidders_at_hcoss.uia.ac.be (Jan.Hidders)
>wrote:
>> The other part comes from the fact that it allows you to define a
>> unifying view over all the data in the external schemas that is not
>> biased towards certain external schemas and also not biased towards
>> certain internal schemas. It is this that becomes threatened when you
>> start introducing ordered tables and this is why non-logical issues also
>> become important for choosing the best logical data model.
>
>How about just ordering views aka relations?

In the external schema you can order as much as you like.

> When it comes time to implement, don't I perhaps want to "bias"
> towards a specific schema?

Yes, that's what you do in the internal schema, but *not* in the conceptual schema. I assume you still know what the purpose of having the three layers was.

> Anyway, if I define different views with different sorts, I'm not sure
> there's any bias. Even "order on a table" can just be a view plus a sort,
> "select * from mytable order by akey", rather than a physical ordering.

Again, in the external schema you can choose your favourite data model to represent your data and order all you like.

• Jan Hidders