Re: what are keys and surrogates?
Date: Mon, 28 Jan 2008 13:47:21 GMT
Message-ID: <J1lnj.1621$Tb6.374_at_trndny07>
> Logical representations are representations to users. Physical
> representations are representations to the machine.
The trouble with this definition is that the user of a machine is frequently another machine.
For example, the "user" of a database is frequently an application program. That application program is a machine. It has users. To the users of the app, the "logical level" is the representation they see. The "physical representation" is the representation to the app.
What the user of the app calls the "physical representation" may be identical to the "logical representation" as viewed at the interface between the app and the DBMS.
This is not a fatal flaw. But it does mean that the logical/physical distinction doesn't answer quite as many questions as the c.d.t. regulars generally assume it does. Received on Mon Jan 28 2008 - 14:47:21 CET