I want to thank folks for their thoughtful comments.

I clarified a few design points.

Most importantly, I added four new appendices. For Python programmers, I provided examples of unittest, doctest and epydoc. For Java programmers, I provided examples of JUnit and javadoc.

I use the word denormalization heavily, to make a point to a certain class of developers. Other developers object to the term, since it doesn't have a precise meaning.

The point I often have to make this:

1. 3rd Normal Form is for Updates.
2. Data Warehousing is about Insert and Select …

The comment was eaten by Haloscan, but here's the text...

You need to read Rozhenstein on characteristic functions.

select
sum(case when a < .5 then 1 else 0 end) 'A'
,sum(case when a >= .5 and a < .75 then 1 else 0 end) 'B'
,sum(case when a >= .75 then …

First, let me point out that the Data Cartel ("DBA" means Don't Bother Asking) won't release all the information I requested, so some of this is a guess.

We'll look at a number of dumb-as-a-post SQL techniques. This is proof -- if any were needed -- that bad SQL is worse than …

See PC World, "Top 50 Tech Visionaries ."

I spent some quality time reading RFC's once upon a time. It was the mid '90's and a client had a desktop application that depended on embedded FTP client that submitted batch jobs to a mainframe.

[Note. It was the 90's. Desktop computing …

The problem is this: parsing HTML from a variety of sources to create pleasant, easy-to-manipulate spreadsheets. HTML can represent the same data in a variety of ways, even within a single web site. What we have are several layers of parsing; layers which must be linked with increasingly simplified intermediate …

The updates to Building Skills in Object-Oriented Design cover some notes on testing, Agility and rework, two ongoing themes that can't be emphasized enough.

There were two small updates regarding testability.

First, creating Outcome instances — for testing purposes — does involve an ugly hack of repeating the payout odds. Since we're …

The email from a developer starts with a complaint and moves on to a plea: "I am constantly having to look at "IF o_status = 0". Code would be a lot more compact and easy to read if exceptions were used. Request favor: Please consider blogging about using exception handling vs …

Don't ask why. I can't explain it without violating a Non-Disclosure Agreement.

However, check this out. Search for NMEA Checksum VB.

• http://www.experts-exchange.com/Databases/GIS_GPS/Q_21413235.html
• http://www.codepedia.com/1/Calculating+and+Validating+NMEA+Checksums
• http://www.codepedia.com/1/Taking+Out+the+Garbage:+NMEA+Checksums …

This put me over the edge. Go deh! has a deep analysis of in "Duck Typing Done Right is Wrong ". It took a minute to parse, but the article is excellent. (A less obscure title would quote the original posting properly: '"Duck Typing Done Right" is Wrong', but that's less …