Re: More on identifiers

"David BL" <davidbl_at_iinet.net.au> wrote in message news:03132046-3fd2-4bb1-9e00-cd81ece451c2_at_h2g2000yqg.googlegroups.com...
> Informally I think of abstract identifiers as "internal glue" within a
> relational database. A bit more formally, they are characterised as
> identifiers that could be mapped bijectively to different values
> throughout the database without changing the recorded information.
> One would therefore hope that they aren't visible to end users.
> Due to the projection, all the abstract identifiers have disappeared
> from every relation. In a way, it's like seeing a database within a
> database! The value of the "inner" database records all the facts in
> the /context/ of just one of the items, and therefore has no need for
> abstract identifiers to glue things together.
>

> Flattening of DVAs requires introduction of abstract identifiers that
> are internal to the database, and can perhaps be seen as an
> implementation technique to map existing DBMS implementations of the
> flat relational model to a nested version that supports DVAs.
>

Do you remember Neo and his attempt to come up with a database (a language, really)
that could capture all facts, no matter how they were structured?

Are we going down this same road again? Received on Sat Jun 06 2009 - 13:46:46 CEST