Re: Transaction Oriented Architecture (TOA)



topmind wrote:
H. S. Lahman wrote:
Responding to Gagne...

It seems to me the article was most of the way there when it proposes
things like isolating SQL so it is not embedded in the problem solution


I have to disagree with such advice. Isolating SQL is oversold. One
does not swap database vendors often enough to make it worthwhile.
Maybe if you sell a product that is designed to be used by multiple
DB's, such makes sense; but not for most custom apps. It creates more
work and more red-tape. (We have spent gazillion messages on this topic
before.)
Eliminating SQL in the application in TOA/TOP isn't about database vendor independence, its about good design and maintainability.

and emphasizing low coupling between modules.

I've found "coupling" to be a rather subjective property such that it
is a nearly useless catch-phrase these days. (That is until the point
somebody defines it clearly and not tied to subjective criteria, such
as what app part is more likely to change.)
Coupling is a relative term, not subjective--similar to a noise ratio. Coupling describes the interdependence between two related objects. Low coupling is realized when significant changes can be made to one object without affecting the other. High coupling indicates changes can not be made to one without requiring changes to another. In the case of OO and DB, when a mapping exists between the two, the nearer that mapping approaches 1:1 the more tightly coupled the application and DB are. In a 1:1 mapping nothing in the DB can be changed without affecting the application, nor can anything be changed in the application data model without affecting change in the DB.

--
Visit <http://blogs.instreamfinancial.com/anything.php> to read my rants on technology and the finance industry.
.