I've cataloged a third specific case of fundamental failures to understand polymorphism. The first two I've seen a fair number of times. The third seems to be more rare.

1. "How do I determine which subclass an object has?" The Identification problem.

2. "How do I morph an object to …

Two months ago, we looked at some Data Warehouse design information.

It looked like 8 months of work. It might be finished by year-end. Fatal mistake: we gave a "number". Year-end.

We did due diligence, investigating source applications, data marts, subject areas, etc. And, the client delayed their decision-making process …

It's easy to prevent successful use case analysis: make it into an exercise of defining lots of "processes" in excruciating detail.

First, ignore all "objects" definition. All business domain entities -- and actors -- must be treating as second class artifacts.

Second, define everything as a process. A domain entity is just …

I've run in to some Agility questions recently. Questions that indicate that some people just don't like the Inversion of Control aspect of Agile methods.

We used to call IoC "Emergent Behavior". The system isn't designed from top-down to fill specific use cases. Instead, the system is designed so that …

One of the Agile practices is Continuous Integration.

Fowler suggests that everyone commits every day. In Elssamadisy's book includes specific advice on why a daily check-in helps.

Some folks call this the "Don't Break the Build" practice.

But what does that mean for Python where there is no build? And …

We have a design, we have code and we have tests that all pass.

Tuesday, we got some new input data that just wouldn't work.

What -- if anything -- went wrong?

Agile is as Agile Does

We're following an Agile approach for several reasons.

1. I'm too lazy to draw up an …

Some thoughts for the day

• "Quick And Dirty == Guaranteed Rework"
• "He Who Codes First Loses"
• "Think Once -- Code Twice"
• "Admin's Law: It's Always Permissions"
• "Programmer's Law: If it's not permissions, it's the path"
• "If it seems hard, you're doing it wrong"
• "One-Off == The First of Many"
• "Requirements Translation: Never == Rarely …

I got a bug report (back in April) about an exercise in Building Skills in Python. It was a change from 2.2 that I never validated in 2.5. Thanks to my readers for responding with questions and complaints.

I've finally updated and posted the revisions.

Further, after some …

Here's an amazing Stack Overflow question.

The follow-up conversation is great stuff.

The question shows two versions of approximately the same processing. Python is faster than Java. That's unexpected.

Java has static compilation and the hot-spot translation to machine code. Apparently, Python has some optimizations that are just as valuable …

A resume is a slippery thing -- a package of semi-structured data.

It has a kind of database-like feel to it, but there are so many exceptions and special cases that the database never works out quite the way you wanted.

For example, I've got -- essentially -- one employer over the past …