Re: Mixing OO and DB

From: David Cressey <cressey73_at_verizon.net>
Date: Tue, 12 Feb 2008 17:04:23 GMT
Message-ID: <rkksj.2676$CX2.933_at_trndny09>


"Patrick May" <pjm_at_spe.com> wrote in message news:m24pce1izn.fsf_at_spe.com...
> "David Cressey" <cressey73_at_verizon.net> writes:
> > "Robert Martin" <unclebob_at_objectmentor.com> wrote:
> >> Tables expose data and have no behavior. Objects hide data and
> >> expose behavior.
> >
> > I have a different understanding.
> >
> > Objects do not always hide data. Specifically, they pass messages to
each
> > other in the form of data.
>
> Some messages may contain data, but many do not. Consider this,
> for example:
>
> Thread someThread = new SomeThreadImplementation();
> someThread.run();
>
> Unless you're considering the name of the class and/or the name of the
> method to be data, the message is solely about behavior.
>

The stuff that's being passed from one side of the assignment to the other is data.
What else would it be?

> > Going further, objects do not "see" the behavior of other objects.
> > What they see is the data, written into messages, that is the result
> > of behavior.
>
> Objects can invoke the behaviors of other objects without needing
> to monitor for any results.
>

I didn't say anything about what they need to monitor or don't need to monitor. I only stated what they see and what they do not see. All they see is data.

> > One could do a data centric analysis of an object world, by
> > analyzing the data passed among the objects in that world.
>
> That would miss a great deal of information in a behavior-centric
> system.
>

How does one express information without using data? Received on Tue Feb 12 2008 - 18:04:23 CET

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