Saturday, June 9, 2007

False Economies

As I get older and more experienced in the IT game some basic truths continue to rear theirs head... One I am currently running into is the idea of not doing some standard practice thing because it will “take to long” or “cost too much money” to do.
I have no problem with not doing some because it is too expensive, however when you are building a business critical application for a publicly traded, Tier 1 company, you had better make sure that those things that you are not going to implement don’t bite you in the ass later.
Documentation and Unit testing should not be negotiable. Especially around business object and other lower level layers. If these layers are not working correctly, how can the layer dependent on these be reliable?
One thing I see more often than I like is not putting enough emphasis on DB design. If you are using a very basic OO model and the DB is literally just a persistence layer then I am all for ORMs. If you have complex set based structures, hire a good DB geek that can architect a proper data persistence approach in terms of DB design and helping with Data Access. Often a developer is not the right person to be doing this.
(I think I have already emphasized this enough on this blog)
Another issue is allowing for future changes. Udi Dahan proposed a design principle which I agree with and employee:
For any classes A and B in a system where both A and B have behavior, A should interact with B through an interface.
The interface which separates two concrete classes should be packaged separately from either of those classes
By employing the strategy above, you allow for the ability to have tests to isolate each “layer”. You also then allow for changing of dependency. As long as the new class implements the original interface, how the business logic occurs is irrelevant. This came up specifically this week with regards to the data access layer. Using this strategy we could investigate different options in terms of the DA, such as using the current implementation, a modified version of the current, an ORM or a Generated layer based on the DB schema. If this had been done earlier it would have take lesser than a minute for each class. Not really a huge time loss there.

I dont take all of this as bad things, it is learning from mistakes, whether they be yours or others. The point is we need to learn from them so we can find ways to avoid or fix future encounters.

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