Re: acceptable way to program
From: Chris Smith (cdsmith_at_twu.net)
Date: 01/02/05
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Date: Sun, 2 Jan 2005 10:28:44 -0700
Chris Uppal <chris.uppal@metagnostic.REMOVE-THIS.org> wrote:
> It may help to consider the difference between:
>
> a) a program (or group of closely related programs) that
> happens to require (ACID) persistence.
>
> b) a program that is required to manipulate independently-existing
> data in a more-or-less public repository (database).
Indeed, I do find that to be a useful distinction. But,
> In my opinion, O-R technologies are mostly about (a) -- that is to say they
> provide a poor man's object database.
This isn't exactly true. There are a number of factors to consider when
making use of O/R mapping technologies, and this is one of them. Some
such technologies are extremely limited in terms of how their data is
stored, and are only suitable for application-private data that uses a
relational database by coincidence. Others are considerably more
flexible, and can deal with data that's represented in a number of ways,
and map from there to a number of different OO models.
Hibernate is a good example of the latter. I enjoy using Hibernate
because I can do (or get someone else to do) intelligent database design
without thinking of my application, and then I can pretty easily create
an OO model of that data using Hibernate that's fairly easy to use from
Java. Same goes for a pre-existing database. Indeed, I can create
different OO models for different applications (which ought to be the
way O/R mappers are used; good O/R mapping is a functional concern, and
is not inherent in the data itself) and they will work together
flawlessly, making connections to the same database.
That said, I know of no O/R mapper that's really universally outstanding
in being able to map an existing database schema in an ideal way.
Generally, you'll end up with some quite quirks in the OO model of the
data. I imagine more flexibility could be provided by products in the
future. Nevertheless, I don't think it's fair to characterize use of an
O/R mapper for this as a hack, or to claim that it's different from the
intended usage of the tool.
-- www.designacourse.com The Easiest Way To Train Anyone... Anywhere. Chris Smith - Lead Software Developer/Technical Trainer MindIQ Corporation
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