Michele Finelli: Software engineering during the Italian Renaissance

My first Plone conference was in Vienna. Glad to be here now.

Everything begins in ancient Babylonia. They had problems like measuring the size of fields after a flood. So they developed geometry (in Egypt too). They had to solve quadratic equations, like this:

a*x*x + b*x + c = 0

They used a different formula than what we are used to, because they had difficulty with the concept of negative numbers: you cannot have a field with a length of minus one meter.

This is basically software engineering, right?

Fast forward to the Renaissance. It is the year 1494, and Luca Pacioli publishes a book on mathematics. He said that the cubic equation (similar to the last, but raising to the third power) would probably never have a general solution. He was wrong. I show you a solution in Python, taken from Wikipedia.

Scipione dal Ferro found a solution a few years later. He seems to have come up with an algorithm to calculate it. Start with a formula, turn this into a series of instructions, and you have an algorithm.

Enter Gerolamo Cardano, Niccolo Tartaglia, and Lodovico Ferrari, all from the sixteenth century. Tartaglia also found a solution, shared it secretly with Cardano, who taught it to his student Ferrari. Cardano found the original solution from Dal Ferro, thought himself no longer sworn to secrecy, and eventually published the solution with Ferrari, together with a solution for the quadratic equation. Tartaglia (nickname for stutterer) became an enemy, and they fought mathematical battles, and we have some papers from this.

When you calculate with cubic roots, part of the solution uses the square root of minus one. At the time this was garbage. Currently we know this as an imaginary number. So it raised questions, which were finally answered two centuries later by Lagrange, Gauss, Ruffini, and Abel, between 1770 and 1826.

Why did this take so long? They lacked the abstractions needed to move forward. Babylonians did not know how to deal with negative numbers. Dal Ferro and company did not know how to deal with imaginary or complex numbers.

Moving forward. Is there a field where the lack of abstractions is preventing progress. I think yes, and it is called software engineering.

• How do we specify what a software should and should not do?
• How do we validate the behavior of code we write?
• How do we describe our architectures?

The answer is currently text: sentences, diagrams, graphs.

The history of the discovery of the mathematical solutions was a tale to tell that in science, progress usually stalls until we are able to go from one language to another. In software, of course there are new programming languages, but I don't mean that.

The Agile Manifesto tells fruitful and interesting things, and gives important results. But it does not improve how we do the software thing.

Software has built a different world, just for example the internet. It should also be a better world. Privacy is going down, are we building a police world, without intending to?

We need a quest to find a better theory of software.