Offline data processing system of the BESIII experiment

The BESIII experiment has been operating since 2009 and has received several upgrades, to study the τ τ -charm physics utilizing the BEPCII accelerator. The BEPCII is a double-ring multi-bunch collider with a luminosity of 1 × 10³³ \, cm⁻² \, s⁻¹ 1 × 10 33 cm - 2 s - 1 optimized at a center-of-mass (cms) energy of 2 × 1.89 2 × 1.89 GeV. The rich physics topics, long lifetime and the large volume of data present challenges to offline data processing. This paper describes the design and implementation of the offline software system to meet the requirements and challenges of BESIII, including offline software architecture, geometry management, database management, event data model and tag-based analysis.