According to the PMBOKGuide, specifically within the Sequence Activities process of Project Schedule Management, there are four types of dependencies used to define the logical relationship between activities.
* Mandatory Dependencies: These are also known as " hard logic " or " hard dependencies. " They are legally or contractually required or inherent in the nature of the work. These dependencies often involve physical limitations. For example, on a construction project, you cannot build the walls until the foundation is poured and set. This is a physical requirement of the work itself.
* Attributes: Mandatory dependencies are typically fixed and cannot be easily changed by the project team without changing the fundamental nature of the project or violating legal/safety standards.
Why the other options are incorrect:
* B. Discretionary: Also known as " preferred logic, " " soft logic, " or " preferential logic. " These are based on best practices or specific sequences desired by the team even though other sequences are possible. They are not legally or physically required.
* C. Internal: These involve a precedence relationship between project activities and are generally within the project team's control. While a dependency can be both mandatory and internal, the question ' s specific definition of " legally/contractually required " points directly to the classification of Mandatory.
* D. External: These involve a relationship between project activities and non-project activities (e.g., waiting for a government permit or a delivery from a vendor). While these can be mandatory, the primary definition of work inherent to the nature of the task and physical limitations is the hallmark of a Mandatory dependency.