Project Management Triangle (Triple Constraint)

The model provides a simple yet powerful 框架 for understanding the trade-offs in project management. The three constraints are often depicted as the vertices of a triangle, with quality as the central theme. The core idea is that no single constraint can be altered without affecting at least one of the others. For instance, if a client wants to add features (increase scope), the project will require more time, more money, or both. If the budget is cut (decreased cost), the project might take longer or have its scope reduced. Similarly, shortening the timeline (decreased time) may require more resources (increased cost) or a reduction in features (decreased scope).

This model is crucial for managing stakeholder expectations. It provides a clear language for project managers to explain the consequences of requested changes. While the original model, often attributed to Dr. Martin Barnes in 1969, is simple, modern interpretations have expanded it to include other constraints, such as risk, resources, and customer satisfaction, sometimes depicted as a six-pointed star or project management diamond. Despite these extensions, the core concept of the time-cost-scope trade-off remains a fundamental principle in project management education and practice, serving as a constant reminder of the balancing act required for successful project delivery.