Matteo Vaccari

Matteo Vaccari

It is possible to write software that solves real business problems, cheaply and reliably. The recipe is well known, even though it's not easy to do.

I am an Extreme Programmer. I help individuals, teams and organization become more effective. I'm lucky to work as a developer for ThoughtWorks, mostly in the Milano area. I used to teach at Università dell'Insubria.

Current stuff

Older stuff

AK We looked at Java very closely in 1995 when we were starting on a major set of implementations, just because it's a lot of work to do a viable language kernel. The thing we liked least about Java was the way it was implemented. It had this old idea, which has never worked, of having a set of paper specs, having to implement the VM (virtual machine) to the paper specs, and then having benchmarks that try to validate what you've just implemented—and that has never resulted in a completely compatible system.

The technique that we had for Smalltalk was to write the VM in itself, so there's a Smalltalk simulator of the VM that was essentially the only specification of the VM. You could debug and you could answer any question about what the VM would do by submitting stuff to it, and you made every change that you were going to make to the VM by changing the simulator. After you had gotten everything debugged the way you wanted, you pushed the button and it would generate, without human hands touching it, a mathematically correct version of C that would go on whatever platform you were trying to get onto.

The result is that this system today, called Squeak, runs identically on more than two dozen platforms. Java does not do that. If you think about what the Internet means, it means you have to run identically on everything that is hooked to the Internet. So Java, to me, has always violated one of the prime things about software engineering in the world of the Internet.


SF If nothing else, Lisp was carefully defined in terms of Lisp.

AK Yes, that was the big revelation to me when I was in graduate school—when I finally understood that the half page of code on the bottom of page 13 of the Lisp 1.5 manual was Lisp in itself. These were "Maxwell's Equations of Software!" This is the whole world of programming in a few lines that I can put my hand over.

I realized that anytime I want to know what I'm doing, I can just write down the kernel of this thing in a half page and it's not going to lose any power. In fact, it's going to gain power by being able to reenter itself much more readily than most systems done the other way can possibly do.

Alan Kay, interviewed on ACM Queue