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Computing Technical Design Report
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Computing Technical Design Report
The high-level goals of the ATLAS offline software are to process the events delivered by the ATLAS trigger and data acquisition system [3-1], to deliver the processed results to physicists within the ATLAS Collaboration, and to provide tools for them to analyse the processed information in order to produce physics results. Technical requirements include the processing time and memory consumption per event necessary to meet financial constraints, and the physics performance requirements encompasses the ability to reproduce faithfully details of the underlying physics processes based on the detector data.
The fulfilment of the processing requirements requires the provision of simulation tools whereby the performance of the software may be tested against a true knowledge of the underlying physics processes. This capability has also been used to aid in the design of the detector and data acquisition hardware.
The complexity and scale of ATLAS mean that the software must be highly modular and robust, and must furthermore be flexible enough to meet the needs of the experiment throughout its operational lifetime. There will no doubt be changes in the physics goals and even detector hardware during this period and the software must accommodate these.
The complexity of ATLAS and the underlying physics require a sophisticated real-time trigger system and components of the offline software should be capable of operating in the trigger environment alongside components designed specifically for it. In general it should be possible to migrate offline processing components into the high-level trigger environment as the physics goals of the experiment change over its lifetime.
The design and implementation of this software requires the establishment of a software development environment capable of supporting a distributed development model appropriate for the widely geographically dispersed ATLAS developer community, and the provision of testing and quality assurance tools to ensure that the software meets both the technical and physics performance requirements.
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