Some project management methods will baseline the scope in a Project Initiation Document or Project Charter. In software companies scope is often defined at a high level in a Statement of Work, which forms a legal contract with the customer, the detail is then worked out in a Design Document.Scope Baseline
The PMBOK defines the Scope Baseline as "the approved version of the scope statement, WBS and the WBS dictionary". The baseline is used to assess the impact of changes and in the management of the project scope. It is essential to baseline the project scope in order to manage scope creep.