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

From: Frans Bouma [C# MVP] <perseus.usenetNOSPAM_at_xs4all.nl>
Date: 14 Jun 2006 09:41:31 GMT
Message-Id: <xn0engran6an0o000@news.xs4all.nl>


Mark Nicholls wrote:

>
> Frans Bouma [C# MVP] wrote:
> > Robert Martin wrote:
> >
> > > On 2006-06-01 23:09:37 +0200, Bob Badour
> > > <bbadour_at_pei.sympatico.ca> said:
> > >
> > > > phlip wrote:
> > > > >
> > > >> An application should have its SQL statements in only a few
> > > modules, and >> all others should be SQL-free.
> > > > >
> > > >> Note in my statement, you can replace SQL with GUI, XML, ORB,
> > > etc, to >> generally the same effect. The point of modules is to
> > > isolate and >> encapsulate.
> > > > >
> > > >> Is that so hard?
> > > >
> > > > Define: few
> > >
> > > The best answer is "one". We would like all the SQL to be placed
> > > in one module, or one group of modules that are all related. More
> > > importantly we want that module (or that group of modules) to be
> > > independent. No other modules in the system should know that it
> > > (they) exist(s). All dependencies point AWAY from the SQL
> > > modules.
> > >
> > > |App Modules|<------|SQL MODULE(S)|
> >
> > erm, shouldn't that arrow be in the opposite direction? I mean, how
> > can an app module function if it needs to consume data from a
> > persistent storage when it doesn't know of a module which can
> > provide that data for him? But this might be an interpretation
> > error from my part: I interpret your diagram as : SQL MODULES are
> > depending on App modules, something I don't see as logical as A
> > <--- B suggests that B uses A thus A <---- B is a using
> > relationship. Or am I missing something? (could be, my UML is a
> > little rusty ;))
> >
> > FB
>
> Hello, spoken to you at the developmentor group.
>
> no, this is an example of Mr Martin's (errant) DIP notion.
>
> The normal model of design would be to go.
>
> App----->data interface<-------SQL modules.
>
> for some reason Mr Martin is obsessed with putting the data interface
> inside the app.
>
> (we have agreed to differ about this, lifes too short.).

        Thanks Mark for the clarification :)

                FB

-- 
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Lead developer of LLBLGen Pro, the productive O/R mapper for .NET
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Microsoft MVP (C#) 
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Received on Wed Jun 14 2006 - 04:41:31 CDT

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