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6 - PROJECT TIME MANAGEMENT

In PDM, finish-to-start is the most commonly used type of precedence relationship. The start-to-finish relationship
is very rarely used but is included to present a complete list of the PDM relationship types.

Finish to Start (FS)
Activity A Activity B

Activity A Activity A
6
Start to Start (SS) Finish to Finish (FF)

Activity B Activity B

Start to Finish (SF)

Activity A Activity B

Figure 6-9. Precedence diagramming Method (PdM) relationship types

6.3.2.2 dependency determination

Dependencies may be characterized by the following attributes: mandatory or discretionary, internal or external,
as described below. Dependency has four attributes, but two can be applicable at the same time in following
ways: mandatory external dependencies, mandatory internal dependencies, discretionary external dependencies,
or discretionary internal dependencies.
• Mandatory dependencies. Mandatory dependencies are those that are legally or contractually required
or inherent in the nature of the work. Mandatory dependencies often involve physical limitations, such
as on a construction project, where it is impossible to erect the superstructure until after the foundation
has been built, or on an electronics project, where a prototype has to be built before it can be tested.
Mandatory dependencies are also sometimes referred to as hard logic or hard dependencies. Technical
dependencies may not be mandatory. The project team determines which dependencies are mandatory
during the process of sequencing the activities. Mandatory dependencies should not be confused with
assigning schedule constraints in the scheduling tool.

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©2013 Project Management Institute. A Guide to the Project Management Body of Knowledge (PMBOK Guide) – Fifth Edition 157

Licensed To: Jorge Diego Fuentes Sanchez PMI MemberID: 2399412
This copy is a PMI Member benefit, not for distribution, sale, or reproduction.