GEANT4: simulation for the next generation of HEP experiments

GEANT4 (RD44) is a world-wide collaboration of scientists aiming to create the detector simulation tool kit necessary for the next generation of HEP experiments. A large variety of requirements also come from heavy ions physics, CP violation physics, cosmic rays physics, medical applications and space science applications. In order to meet such requirements, a large degree of functionality and flexibility has to provided. GEANT4 is exploiting Object Oriented Technology to achieve these goals. The most relevant Object Oriented methodologies have been studied and a large number of tools and libraries have been investigated and evaluated. An overview of the GEANT4 analysis and design model will be given and the main components of the object models discussed. The main functionality of a first prototype will also be described. An overall view of the collaboration's structure and strategy will also be given. (author)