According to the PMBOK Guide (Project Schedule Management), specifically within the Sequence Activities process, dependencies are categorized to define the logical relationship between activities.
Discretionary Dependencies are those established based on knowledge of best practices within a particular application area or where a specific sequence is desired, even though there may be other acceptable sequences.
* Logic and Best Practices: These are sometimes referred to as " soft logic, " " preferred logic, " or " preferential logic. " They are often based on historical information or " lessons learned " from similar projects where a specific sequence proved to be most effective.
* Risk of Fast Tracking: Because these dependencies are not physically or legally mandatory, they are the first to be reviewed when the project team performs Fast Tracking (a schedule compression technique).
Compressing a schedule by overlapping activities with discretionary dependencies increases risk because the " best practice " sequence is being bypassed.
* Documentation: Discretionary dependencies should be fully documented, as they can create arbitrary total float values and can limit later scheduling options.
Analysis of Distractors:
* A. External: These involve a relationship between project activities and non-project activities. These are usually outside the project team ' s control (e.g., waiting for a government environmental hearing).
* B. Internal: These involve a precedence relationship between project activities and are generally within the project team ' s control (e.g., a machine cannot be tested until the team assembles it).
* C. Mandatory: These are " hard logic " dependencies that are legally or contractually required or inherent in the nature of the work (e.g., you cannot hang a door until the wall frame is built). There is no " discretion " or " best practice " choice involved; the sequence is physically necessary.