Re: Mixing OO and DB

From: Cimode <cimode_at_hotmail.com>
Date: Fri, 21 Mar 2008 16:21:12 -0700 (PDT)
Message-ID: <386f490f-990b-467d-a5cb-f130363bc286_at_s37g2000prg.googlegroups.com>


On 21 mar, 22:14, Patrick May <p..._at_spe.com> wrote: [Nonsense snipped]
> Some representations are more expressive in terms of the problem
> or solution domain.
BS. What is a solution domain.

>Tuples are not always the optimal data structure.
Tuple is not a structure. Relation is

> > If the transposition is done by the DBMS, then it can retain its
> > responsibility for guaranteeing integrity. If the transposition is
A DBMS having *responsibility*

> > done by the application, then that responsibility may need to shift
> > from the DBMS to the application--every application. Now you have
> > to guarantee that the code that is used to access the information is
> > identical in every application that uses the information

> If that is a requirement, it's a good argument for a shared
> mapping layer or other decoupling mechanism. In fact, though,
> different applications often need different representations of
> different subsets of the data available in a relational database, plus
> data that is only used within the application. Because the
> application has a different, non-relational model of the data,
> decoupling is good design.
Based on the presented meanigless arguments that's quite a conclusion.

> > --AND, you have to prevent ad-hoc access to the data.
>
> Why? It's certainly easier to maintain the integrity of the
> database if you can, but many systems support multiple applications
> and ad-hoc interaction with the underlying database. That's what
> locking and other concurrency techniques are for.
>
> > In addition, you have to manage concurrency in every application.

>
> > Keep it simple, stupid: let the DBMS do what it is designed to do.
> > Why reinvent the wheel? The people who built the DBMS are probably
> > a lot smarter than you, or at least know more about how to persist
> > information than you, since that is their focus.
>
> A relational database is a very generic technology.
Question: what is a generic technolo

> An application is much more specific and can therefore take advantage of
> less general types and data structures that improve the performance
> and maintainability of the application code.
BS. Prove it.

What performance? Response time? Concurrency ? Sloppy as usual

> Except for CRUD systems,
> the database vendors can't address those problem domains in a generic
> way.
That (solution) domain thing is just the biggest bulshit you have been pourring down on this thread/

> >>>> Further, the view that the schema is integral to the
> >>>> application is very data centric. Different applications may
> >>>> need the data in different forms, not all of which are
> >>>> relational.
BS. What is a *different form* for data ? Meaningless.

> There is therefore a need to translate between the
> >>>> data structures, which is another good reason to decouple the
> >>>> application from the specific physical schema being used.
Blah blah blah....(yawn....)

> >>> If by data centric you mean that the information that is to be and
> >>> can be recorded must be specified before even considering how that
> >>> information may behave, then I agree: it is a data centric view.
>
> >> It is also possible to define a system in terms of behavior and
> >> only decide on a particular data representation once those
> >> behaviors are designed. In practice, both approaches are typically
> >> used.
>
> > How can you possibly design a system in terms of the behavior of
> > objects if you haven't first specified which objects are
> > interesting?
>
> You focus on the behaviors of interest and partition those
> behaviors into cohesive units of classes and modules.
Cohesive units of classes ? Bullshit. He asks for a specification and you answer by a vague obscure concept.

> >>> But again, you're laboring under the delusion that an application
> >>> must be tied to a physical schema.
>
> >> I'm under no such delusion.
Yes you are. You are just burried in it to see it.

> An application implementation that
> >> uses data from a relational databas must deal with a particular
> >> schema. Since the two change for different reasons and since the
> >> models are often different, decoupling them is good design.
No you idiot, you have no clue what is *good design* and never will. A normalized schema is the simplest thing to modify.

> > Whenever there is a change in potential information content, that
> > change may involve potential information that an application can
> > access or manipulate, or potential information that an application
> > doesn't access.
>
> Fallacy of the excluded middle. The change may also be in how
> the information is modeled by either the application implementation or
> the specific schema being used by the application. One option is to
> use views to isolate the two. Another option is to decouple the two
> components (application implementation and specific schema) so that
> changes in one do not impact the other.
Do you have discounts at K Mart for repeating the *decouple* term.

> >>>>>> Even if an application uses the database system's
> >>>>>> capabilities to implement some application functionality, there
> >>>>>> are still changes to the underlying schema that do not, or
> >>>>>> should not, require change to the applications that use that
> >>>>>> schema. This is why approaches like dependency inversion are
> >>>>>> useful. The application depends on an interface and the
> >>>>>> combination of database schema and any logic running in the
> >>>>>> database implements that interface. Either can change without
> >>>>>> impacting the other.
>
> >>>>> The database contains that which can be manipulated. An
> >>>>> application is that which does the manipulating. These are
> >>>>> completely different species of functionality.
>
> >>>> The database sometimes contains some of that which can be
> >>>> manipulated.
>
> >>> I don't follow you. Please elaborate.

> >> Not all data used by an application needs to be in the database.
Where should it be then? Are you implying that we should multiply the points where it is to be administered/

> > I thought that we were discussing information that is to be and can
> > be recorded. Such information needs to be in the database.
>
> That depends on how long it needs to remain available and if it
> needs to be accessed by other clients of the database. I often work
> on systems where a considerable portion of the information is stored
> in a distributed shared object repository, in memory.
Most systems do not work that way or how to make a hasty generalization from a specific case.

> You could
> consider that a form of database, but it doesn't use a relational
> model.
In your dreams. Only an ignorant would call a data bag a database.

I imagine what crappy system it must be.: no integrity, accuracy, data losses..users running behind understanding the results and summaries...

> Sincerely,
>
> Patrick
>
> ------------------------------------------------------------------------
> S P Engineering, Inc. | Large scale, mission-critical, distributed OO
> | systems design and implementation.
> p..._at_spe.com | (C++, Java, Common Lisp, Jini, middleware, SOA)
Received on Sat Mar 22 2008 - 00:21:12 CET

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