What is Software Engineering?

Earlier in my career, I would say my career was software engineering. Then one day an interviewer asked "What do you mean by that?" This simple question was the beginning of my search to really understand what software engineering meant. My first answer was
awkward and used thoughts that can be found in the CMM. After thinking about it for a few years I began to believe that Software Engineering was an oxymoron. I used the term software development. Wasn't I clever ;-) Then I discovered Agile Software Development and I was hooked. I wrote about it, taught it, practiced it, loved it. This lasted for a few years, but the more I saw the more I realized there are lots of ways to be "Agile". Some were sound and others weren't, but they all could say (without lying) that they were Agile! I knew what worked for me, but did that always work? Off the shelf agile methods (like XP) work great in some places, but not so great in others. Many projects had constraints that most agile practitioners hadn't even considered (let alone little ole me).

My approach to new problems is to go back to first principles. In this case what were those principles. The agile alliance has these, but they seem more like good ideas from experience rather than principles. This got me thinking. Maybe there is something in that old term Software Engineering. Maybe it would help to dissect the term:

Software: Coded instructions (programs) that make a computer do useful work. (from www.krollontrack.com/legalresources/glossary.asp)

Engineering: Engineering is the application of science to the needs of humanity. This is accomplished through the application of knowledge, mathematics, and practical experience to the design of useful objects or processes. (From wikipedia)

Let's see if I can munge the above definitions to create something I like...

Software Engineering: The application of knowledge, techniques, and practical experience to make a computer do work deemed useful.

This still doesn't get me to the principles. Civil Engineers have a wealth of physical principles (Newtonian physics and all that). The best Software Engineering can counter with is Computer Science. It hasn't really progressed since second order programming languages and the best I can figure it's principles boil down to logic and some rule about a Turing machine. So I have just alienated my CS doctorate crowd. One less reader won't hurt me ;-o

I have thought on this and in the past the best I could come up with was to steal principles from other disciplines. I would rationalize it like the definition for software engineering found in the wikipedia. This defintion makes Software Engineering nothing more than a mutt grown from other more pure fields (science, management, physiology and my favorite the generic "engineering"). Well that just doesn't cut it for me. There are some rules behind this activity called Software Engineering and if you break them it causes you pain. Let see if I can find them....