Modern software systems are built by composing components drawn from large repositories, whose size and complexity is increasing at a very fast pace. A fundamental challenge for the maintainability and the scalability of such software systems is the ability to quickly identify the components that can or cannot be installed together: this problem is related to boolean satisfiability and is known to be algorithmically hard.
We will survey the main results of this research area, obtained over the past ten years, and then step back for a moment to identify the key prerequisites that made all this work possible.
This will lead us to elicit the need to building a universal archive of the source code publicly available, and we introduce the Software Heritage project, that is taking over the challenge of building such an archive over the long term.

Roberto Di Cosmo holds a PhD in Computer Science and is currently Computer Science professor at University Paris Diderot, after teaching for almost a decade at Ecole Normale Supérieure in Paris, and spending a few years at INRIA.
He has been actively involved in research in theoretical computing, specifically in functional programming, parallel and distributed programming, the semantics of programming languages, type systems, rewriting and linear logic. He focus now on new scientific problems posed by the general adoption of Free Software, with a particular focus on static analysis of large software collections, that were at the core of the european reseach project Mancoosi.
Following the evolution of our society under the impact of IT with great interest, he is a long term Free Software advocate, contributing to its adoption since 1998 with the best-seller Hijacking the world, seminars, articles and software. He has created theFree Software thematic group of Systematic in October 2007, and is the director of IRILL, a research structure dedicated to Free and Open Source Software quality.