What, exactly, the definition of a baseline is depends on your role and perspective on the SDLC (Software Development Life Cycle) process. The baseline concept plays in many aspects of SDLC execution, including project management, configuration management, and others. Additionally, the baseline concept and practice is applicable to all the SLDC methodologies, including, but not limit to the, Agile Model, Waterfall Model, Iterative Model, Spiral Model, and V-Model.
A baseline is a reference point in the software development life cycle marked by the completion and formal approval of a set of predefined work products for phase completion. The objective of a baseline is to reduce a project’s vulnerability to uncontrolled change and to provide a point in time set of artifacts for references and recovery, if necessary. Baselining an artifact (requirements specification matrix, design, code, data model, etc.) moves it into formal change control (usually, in one or more repository tools) at milestone achievement points in the development life cycle. Baselines are also used to identify the essential software, hardware, and configuration assembly components that make up a specific release of a system.