**4.2 AliRoot**

AliRoot [46] is the ALICE software framework for reconstruction, simulation and analysis of the data. It has been under a steady development since 1998. Typical use cases include detector description, events generation, particle transport, generation of "summable digits", event merging, reconstruction, particle identification and all kinds of analysis tasks. AliRoot uses the ROOT [40] system as a foundation on which the framework is built. The Geant3 [47] or FLUKA [48] packages perform the transport of particles through the detector and simulate the energy deposition from which the detector response can be simulated. Except for large existing libraries, such as Pythia6 [49] and HIJING [50], and some remaining legacy code, this framework is based on the Object Oriented programming paradigm and is written in C++.

AliRoot is constituted by a large amount of files, sources, binaries, data and related documentation. Clear and efficient management guidelines are vital if this corpus of software should serve its purpose along the lifetime of the ALICE experiment. The corresponding policies are described in [51]. For understanding and improvement of the

AliRoot performance, as well as for understanding the behavior of the ALICE detectors, the fast feedback given by the offline reconstruction is essential.
