According to the PMBOK® Guide, specifically within the Plan Procurement Management process, the Procurement Statement of Work (SOW) is developed from the project scope baseline and defines only that portion of the project scope that is to be included within a related contract.
Derivation from Scope Baseline: The Procurement SOW is a detailed narrative description of the work to be performed by a seller. It is derived from the Project Scope Statement, the WBS, and the WBS Dictionary.
Purpose and Content: It describes the procurement item in sufficient detail to allow prospective sellers to determine if they are capable of providing the products, results, or services. It includes specifications, quantity desired, quality levels, performance data, period of performance, and work location.
Contractual Relationship: Each individual procurement requires a separate SOW. While the project may have a massive overall scope, a specific SOW for a subcontractor might only cover the " Electrical Wiring " or " Software Testing " portion of that scope.
Evolution: As the procurement process moves from planning to a signed agreement, the SOW may be refined and eventually becomes a formal part of the contract.
Comparison with Other Options:
Product scope description (A): This describes the features, functions, and characteristics of the product, service, or result. While it informs the SOW, it is a broader document that defines the entire " what " of the project, not specifically the contracted portion.
Project schedule (C): This is a model that links activities with planned dates, durations, and milestones. While a contract will have a schedule, the schedule itself does not define the " portion of the scope " to be included in the contract; that is the role of the SOW.
Work breakdown structure (D): The WBS is a hierarchical decomposition of the total scope of work to be carried out by the project team. It is a component of the Scope Baseline, but it covers the entire project, not just the portion assigned to a specific external seller.
