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

> Maybe I'm missing something, but cant you see it was an example of 'change'.

Correct me if I am wrong, does 'change' mean that an application should be designed for any type of change, relavant or not? Don't you think there are a cost associated to this? Don't you think that that cost has to be compared to the probability of the change?

> Granted, not a particularly likely occurring example for software
> written for in house use where a certain DB vendor is already standard -
> its just an example.

Maybe you can give some examples of likely changes. Making irrelavant examples doesn't make any sense.

> Robert M could easily have said '...able to change from Oracle to MySql
> to a Wax Drum...'

I am very aware of that Robert M easily could say anything, relevant or not. But he is not supporting his statements by giving irrelevant examples.

> The example is pointing out that Robert and Co's desire is to have an
> application design which is DBMS neutral - the DBMS can be a Relational
> one, a Hierarchical one or even a Quantum one built to use Wax Drums as
> the physical storage mechanism.

If think that all here agree that relational databases are superior to hierachical databases are in almost every aspect. So switching from relational to hierachical is just another irrelevant example. And I think if we try to prepare our application for the next generation (Wax Drums?) of databases, we would most likely fail whatever we do. Look at an old application using hierarchical databases. To do the same thing as
"select * from company where location=? and name like ?" they needed to write a lot of application code. The interface between the business layer and "persistence" layer would not have been "findCompanyByLocationAndStartingWith", it would have been on a much lower level. It would have been very difficult for the programmers in that time to imagine that one day, it would come a database that could do such a complex thing as "findCompanyByLocationAndStartingWith" in one single statement. Today it is very difficult to tell what complex stuff the "Wax Drums" database will be able to do.

> Can we forget the what the change is to - its not relevant for the
> discussion, its the desire to be able to change thats key.

No, you can't prepare your application for any kind of changes, you need to know what kind of changes that are likely to happen. Today the most likely changes are changes in programming language or OS, theese changes will likely invalidate the entire application, regardless how much you prepare for "changes". (Yes, I know there are some languages that may run on multiple OS).

Fredrik Bertilsson
http://frebe.php0h.com Received on Sat Jun 03 2006 - 20:15:45 CEST