Object oriented reconstruction software for the instrumented flux return of BABAR

BABAR experiment is the first High Energy Physics experiment to extensively use object oriented technology and the C++ programming language for online and offline software. Object orientation permits to reach a high level of flexibility and maintainability of the code, which is a key point in a larg e project with many developers. These goals are reached with the introducti on of reusable code elements, with abstraction of code behaviours and polym orphism. Software design, before code implementation, is the key task that determines the achievement of such a goal. We present the experience with the application of object oriented technolog y and design patterns to the reconstruction software of the Instrumented Fl ux Return detector of BABAR experiment. The use of abstract interfaces impr oved the development of reconstruction code and permitted to flexibly apply modification to reconstruction strategies, and eventually to reduce the ma intenance load. The experience during the last years of development is presented. An iterat ive review and improvement of the design has been strategically applied to the code areas which showed to be, on the basis of experience, more delicat e. (C) 2001 Elsevier Science B.V. All rights reserved.