Re: Object-relational impedence

From: Bob Badour <>
Date: Tue, 04 Mar 2008 10:20:07 -0400
Message-ID: <47cd5a9b$0$4065$>

Jan Hidders wrote:

> On 4 mrt, 00:02, Bob Badour <> wrote:

>>Roy Hann wrote:
>>>"Thomas Gagne" <> wrote in message
>>>>JOG wrote:
>>>>>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.
>>>>The issue as I've discovered it has to do with the fact OO systems are
>>>>composed of graphs of data and RDBs are two-dimensional.
>>That is a remarkably uninformed and ill-conceived sentence. It's rather
>>like comparing boats and cars saying boats have hulls and cars are
>>pretty. Regardless of truth, the comparison is pointless on its face.
>>One can represent any graph on two-dimensional media just as one can
>>represent any relation on two-dimensional media. In fact, since a graph
>>is merely a set of vertices and a set of directed edges and since one
>>can easily represent vertices and directed edges as tuples, one can
>>easily represent any graph using relations.
>>The Great Debate was had about 3 decades ago and graphs lost.
> I beg to differ. What lost was the idea that a close coupling is
> required between how the data is stored and how it is accessed /
> queried, i.e., that in that sense you cannot have data independence.
> But such data independence can be just as well achieved with graph-
> based data models.
> -- Jan Hidders

Well, I have yet to see it. Until I see any real evidence of a graph-based data model with physical data independence, we will just have to disagree. Received on Tue Mar 04 2008 - 15:20:07 CET

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