Re: The wisdom of the object mentors (Was: Searching OO Associations with RDBMS Persistence Models)

From: mAsterdam <>
Date: Fri, 09 Jun 2006 10:11:32 +0200
Message-ID: <44892ca7$0$31642$>

Robert Martin wrote:
> Keith H Duggar said:

>> Robert Martin wrote:
>>> Bob Badour wrote :

[snip insult/fallacy]

>>>> A logical data model provides the structure,
>>>> manipulation and integrity for a formal system. A good
>>>> logical data model imposes no particular structure on
>>>> the data as a whole while it does provide a structure in
>>>> which to represent data. In fact, the structure of the
>>>> data itself depends largely on one's point of view. One
>>>> drastically alters the appearance of any graph by
>>>> starting at a different location and traversing the
>>>> edges in different directions.
>>> I'm with you so far
>> So you agree that, unlike a relational data model, an OO
>> (Network) data model imposes expression bias? In other
>> words, that it creates a asymmetric navigational structure
>> that artificially makes some computations more difficult to
>> express? And do you think this is good? If so why?

> Because it also makes some computations easier.

Which (or which types of) computations are easier?

> An application will often reform data into a
> non-relational structure that eases computation.

"non-relational" as a synonym to "navigational" or did you have something else in mind?

> I'll grant you that the structure may make other compuations
> more difficult. (e.g. it is easier to search a balanced
> tree than to insert).
> Yes, I agree, there is an expressional bias. Indeed that is intrinsic
> to one of the points I've been trying to make (through the loud bluster
> of insults). Applications want to see the data in the form that is most
> convenient to them. This means that the applications should not
> strongly depend on the relational format unless that format IS the most
> convenient form for them.

That goes rather hard the other way:
Consider "Applications should not strongly depend on a navigational format unless that format IS the most convenient form for them.": a matter of convenience for some applications at the cost of convenience for other applications.

This comes close to first come, first serve. If a new idea is sound at some abstract
level it still has to be cost-evaluated
against (and possibly rejected just because of) the navigations in place.

[snip FS] Received on Fri Jun 09 2006 - 10:11:32 CEST

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