Re: Object-relational impedence

From: Bob Badour <>
Date: Mon, 03 Mar 2008 18:24:03 -0400
Message-ID: <47cc7a87$0$4031$>

topmind wrote:

> On Mar 3, 10:54 am, Bob Badour <> wrote:

>>topmind wrote:
>>>JOG wrote:
>>>>On Mar 3, 2:07 pm, Thomas Gagne <> wrote:
>>>>>All attempts by applications to access a DB's tables and columns
>>>>>directly violates design principles that guard against close-coupling.
>>>>>This is a basic design tenet for OO.  Violating it when jumping from OO
>>>>>to RDB is, I think, the source of problem that are collectively and
>>>>>popularly referred to as the object-relational impedance mismatch.
>>>>I wondered if we might be able to come up with some agreement on what
>>>>object-relational impedence mismatch actually means. I always thought
>>>>the mismatch was centred on the issue that a single object != single
>>>>tuple, but it appears there may be more to it than that.
>>>>I was hoping perhaps people might be able to offer perspectives on the
>>>>issues that they have encountered.  One thing I would like to avoid
>>>>(outside of almost flames of course), is the notion that database
>>>>technology is merely a persistence layer (do people still actually
>>>>think that?) - I wonder if the 'mismatch' stems from such a
>>>This came up in a nearby message. I borrowed the following text from
>>The text had too many blatant errors to start enumerating them all.

> Most of them are statements about philosophy or practice rather than
> absolutes; thus its hard for them to be objectively or "blatantly"
> wrong. Whether that's a good thing or not is another issue. I see the
> list as a starting point for discussion even if it does not settle
> everything.
> It brings up interesting questions, such as why not have schema
> inheritance? If inheritance is good or OO, why is it not good for
> relational schema's? The answer is that OO and relational approach
> things differently.

Your question presupposes that inheritance is good for OO. Received on Mon Mar 03 2008 - 23:24:03 CET

Original text of this message