Release Strategies: CMS approach for Development and Quality Assurance

Now that CMS has started data taking there is a balance to be struck between software release stability for operations and the need to improve the physics and technical performance of the code. In addition new code may need to be developed to correct for unforeseen data taking conditions, and has to be integrated into the mainstream releases with a minimum risk. To keep the process under control, CMS uses regular (twice a day) Integration Builds. A complex set of validation steps is used to verify the software at various stagesfrom the regular Integration Builds to running a full s/w and physics validation suite on the grid for major releases. CMS has adopted a development model that tries to strike the correct balance between the needs of stability and a constant improvement; this talk will describe our experience with this model, and tell the story of how the commissioning of the CMS offline has proceeded through the perspective of the past year's releases.