Difference between a dependency and a constraint in project scheduling?

• A. Dependency is a resource requirement; constraint is a risk.
• B. Dependency is a time-based relationship; constraint is cost-based.
• C. Dependency is a logical relationship between tasks; constraint is a restriction that limits schedule options.
• D. Dependency is always external; constraint is internal.

Answer: (C)

In project scheduling, the key distinction is between how tasks relate to each other and the limits that shape when they can be done. A dependency is a logical relationship that defines how the timing of one task is tied to another. It sets the order in which work happens—for example, you must finish one task before starting the next, or two tasks may start together if allowed. This is all about sequencing and how one piece of work depends on another.

A constraint, by contrast, is a boundary that restricts the schedule options. It doesn’t create a relationship between tasks; it imposes a limit on when or how a task can occur. Examples include fixed deadlines, mandated start or finish dates, or limitations due to resource availability. Constraints shape the window in which work can be scheduled but don’t define the inter-task relationships themselves.

So, the correct understanding is that a dependency is a logical link between tasks that governs order, while a constraint is a scheduling restriction that limits options.