Work Breakdown Structure (WBS) estimation method follows several major principles to effectively decompose a project into smaller, manageable components. Some of the key principles include:

1. Hierarchical Structure: The WBS follows a hierarchical structure, where the project is broken down into smaller, more manageable components at multiple levels of detail. Each level represents a progressively detailed decomposition of the project deliverables.

2. Deliverable-Oriented: The WBS focuses on deliverables rather than activities or tasks. It identifies the tangible outputs or results that must be produced to complete the project successfully. This ensures clarity and alignment with project objectives.

3. Mutual Exclusivity: Each work package or component in the WBS should be mutually exclusive, meaning it represents a distinct and independent part of the project. This prevents overlap and ambiguity in responsibilities.

4. Complete Coverage: The WBS should encompass all the work required to complete the project scope. It should leave no gaps or omissions, ensuring that all necessary activities and deliverables are accounted for.

5. Progressive Elaboration: The WBS is developed iteratively and progressively elaborated as more details about the project become available. It starts with high-level phases or deliverables and is gradually refined to include more detailed components.

6. Consistent Decomposition: The decomposition of the project into smaller components should be consistent across all levels of the WBS. This ensures uniformity and facilitates understanding and communication among project stakeholders.

7. Control Account Structure: In large or complex projects, the WBS may include control accounts, which represent major segments of the project with assigned responsibilities and budgets. Control accounts help in monitoring and controlling project progress.

8. Coding Scheme: A coding scheme is often used to uniquely identify each component in the WBS. This facilitates the organization, tracking, and reporting of project activities and resources.

By adhering to these principles, the WBS estimation method provides a structured approach to project planning and management, enabling effective decomposition of the project scope into manageable components and facilitating better control and coordination of project activities.