Difinitive Software Library. The library in which the definitive authorised versions of all software CIs are stored and protected. It is a physical library or storage repository where master copies of software versions are placed. This one logical storage area may in reality consist of one or more physical software libraries or filestores. They should be separate from development and test filestore areas. The DSL may also include a physical store to hold master copies of bought-in software, e.g. a fireproof safe. Only authorised software should be accepted into the DSL, strictly controlled by Change and Release Management. The DSL exists not directly because of the needs of the Configuration Management process, but as a common base for the Release Management and Configuration Management processes.