HKSM

Required sequencing of activities driven by the work itself (physical or technical limits) or imposed by binding obligations such as contracts, permits, codes, or laws.

Key Points

• These are non-negotiable, hard-logic relationships that dictate task order.
• They arise from intrinsic work constraints (physical/technical) or legal/contractual requirements.
• They cannot be changed without altering scope, method, or constraints.
• Identifying them early helps build realistic network diagrams and manage critical path risk.

Example

On a construction project, the foundation must be poured and cured before framing can begin (physical constraint). In addition, an approved building permit is required before any structural work starts (legal requirement). Both are mandatory dependencies.

PMP Example Question

Which scenario best represents a mandatory dependency?

1. The team decides to finish the user interface before the backend to simplify demos.
2. Concrete must cure before load-bearing walls are erected.
3. Installation can start only after the vendor ships the hardware.
4. Work is postponed because the database administrator is on vacation.

Correct Answer: B — A required sequence due to the nature of the work.

Explanation: Concrete curing is a physical constraint that forces the order of tasks, making it a mandatory dependency.