A few days ago I wrote a more generic article on the value of software (can be found here if anyone cares http://softwaredev2k.com/2011/10/understanding-the-value-of-software/) which I updated today to link to this post for the more mathematically inclined.

Great work indeed!

D = (Vn + Vf) / (Ei + Em)

Vn = Value Now
Vf = Future Value
Ei = Effort of Implementation
Em = Effort of Maintenance

Which reduces over time to:

D = Vf / Em

-Max

Peace,
Jenny

-Max

Well, I’ve programmed, mainly for my System Simulation course, and did enough to run it without errors, but it also took a lot of time. All the time, i was drawing flowcharts, and trying to give shape to my ‘liquid’ ideas.

And those who did it in half my time just went Rambo. They kept banging at the keyboard and did it. I was tempted to mouth the proverb about 10000 Donkeys and works of shakespeare, but i realized that i was the one typing for 10000 years.

I’m narrating this anecdote because all those who did it bragged about how they did it by ‘instinct’, artfully etc. You know how collegers brag. But then, college programming is nothing like a major software development activity.

Well, i’m no longer programming regularly, but the glamour of commanding an abject machine slave still charms me. I went through your previous posts and you seem to say exactly opposite of what I used to believe. But hey, you are the real hotshot.

You know, I think it’s possible that you could actually perform a mathematically-rigorous proof of the equation. I haven’t looked into it, but I think it could be possible.

-Max

Although thinking about that, if you’re a library, V_i is probably “reduction of E_m for other projects”, so you might not even have to get too complicated about it.

-Max

I’d say that ultimately, one could measure E_m and E_i across the whole world–one could make seriously bad API choices that would severely increase E_m for users of your library, and that might be something to take into consideration. Usually, though, a “single project” is well-defined, and most of the decisions that I have to make personally are pretty easy to judge just by limiting myself to the factors at hand, that I use my own judgement to determine separately for each individual decision.

The method of measuring V_i is really undetermined at this point. I think that it’s somewhat up to the designer and their goals, really. I think that money is a totally valid way of measuring some of these things for some situations (in fact, you could measure V_i, E_m and E_i all in money and come up with a numerically solvable equation, if you wanted, though it would probably not be a broad-enough measurement of V_i, and determining the monetary value of V_i would be a whole book unto itself), but the total benefit for the world at large is something that I take into account far more often as an open-source developer, I think, than I put value in ROI.

-Max

I believe that each of these points of view is legitimate, and that your equation can be validly applied to each of them (with a proper choice of coefficients, of course); but when going from one POV to the next, part or all of the Ei for each “sub-product” except the first becomes subsumed into the Em for the larger whole, or vice-versa when zooming in.

Now the question arises: Should Netscape have done better by not doing anything? By now, a really huge quantity of manpower and other resources has already been invested in the larger “product” I mentioned earlier. Whether that investment has “paid off” will depend on how one measures the Vi, taking into account, yes, dollars, but also freedom of choice, customizability, etc. Also, should the Vi be measured as a “return on investment” for the peope and legal entities who did invest their labour and/or their money into it, or as the total benefit for the world at large?

(For anybody who takes this too literally, though–E_m is of course the Effort of Maintenance whether you maintain it or not; it’s just the intrinsic maintenance effort that the change will require.)

-Max

oh oops… I should have read further.. you mention that. haha….

“However, there is a critical factor missing from the simple form of this equation: time”

If we say E_m = C * t₁ where C is the coefficient of maintenance and t₁ is time, then it’s the coefficient of maintenance that we care about, though that may itself be a derivative of something else.

-Max