Software process in GEANT4

Since its erliest years of R&D [1], the GEANT4 simulation toolkit has been developed following software process standards which dictated the overall evolution of the project. The complexity of the software involved, the wide areas of application of the software product, the huge amount of code and Category complexity, the size and distributed nature of the Collaboration itself are all ingredients which involve and correlate together a wide variety of software processes. Although in "production" and available to the public since December 1998, the GEANT4 software product [1] includes Category Domains which are still under active development. Therefore they require different treatment also in terms of improvement of the development cycle, system testing and user support. This article is meant to describe some of the software processes as they are applied in GEANT4 for both development, testing and maintenance of the software.