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Identifying Dependencies for Project Management Estimation: One Thing Leads to Another

My wife and I decided to finally tie the knot earlier this year; naturally we wanted our big day to be unforgettable. It wasn’t long before we were stunned by countless details and difficult questions. For instance, we realized that we need to plan the entourage before we can print the invitations, do reservations but not until we received the RSVPs! We were not sure what kind of band to get for the reception, or should it be a pianist? We’ve both dreamed of a beach wedding but it was almost March. We were just overwhelmed.

Wedding planning can be an overwhelming task with a complex network of activities and stakeholders just as much as an average project. They are influenced by the relationships that govern the order in which the work activities are carried out. These are called “dependencies”. They define the delivery method of a project, and ultimately will affect the success of the outcome. 

Dependencies and Constraints, are they the same?

According to ‘A Guide to the Project Management Body of Knowledge’, there’s no precise definition to the term ‘Dependency’, but it refers to this term as a logical relationship among all project activities, or between an activity and a milestone. Wikipedia defines it as; ‘a link amongst a project terminal elements’. 

Constraints are similar to dependencies; they also impact the sequencing of activities. However, a constraint suggests a limiting restriction rather than an interdependency relationship. 


Dependencies dictate when an activity can be performed, which define the sequence among activities. Based on their characteristics, three main categories of dependencies can be identified: 

  • Mandatory dependencies (hard logic), these relate to the nature of the work and often involve physical limitations that cannot change, such as erecting the walls of a house before putting up the roof.
  • Discretionary dependencies (soft logic), these relate to knowledge of best practices that may be at the discretion of the stakeholders and may change from project to project. As an example, one does not need to complete the entire bill of materials prior to beginning procurement.
  • External dependencies, these relate to non-project environment and may be beyond the control of the project manager, such as obtaining a permit from a certain regulatory body.

Activities relate to each other in four types of logical relationships – finish to start, start to finish, finish to finish, and start to start. These are also known as precedence relationships. They may fall under the categories of mandatory or discretionary dependencies. 

Identifying Dependencies

In order to do that, the WBS should be first decomposed into a more comprehensive list of activities along with their attributes. This is an outcome of the Activity Definition process. All predecessor activities, successor activities or constraints should be recorded, with their description as well as any other information about the resources or time that is needed for each.

Brainstorming and expert judgment can be used to understand how the activities are going to be sequenced, particularly when managing a project in an unfamiliar domain. Changes to the Activity list might come up. Assigning durations and dates during the preliminary identification of dependencies should be avoided so one should focus on the logical sequencing of work and integrating higher levels of the WBS.

The amount of resources needed and available for each activity must be kept in mind. Resource availability can also affect the time needed to perform an individual activity. If the ideal resource for an activity is unavailable, an alternate resource may be considered, which may or may not affect the activity’s duration.

Sequencing Activities

Once the dependencies are established and all other inputs are assembled for the Activity Sequencing Process, the project events and activities can be represented in a network diagram. An event is defined as the starting or ending point for a group of activities, and an activity is the work required.

This is when strategic decisions can be made about how to sequence the dependencies among activities. Therefore, one should try as many arrangements as possible and analyze the benefits and drawbacks of each one. This will result in the development of the best possible sequence.

Network diagrams provide valuable input for the planning, integration of plans, time and resource management. They mainly aim to eliminate the need for crisis management by providing a pictorial representation of the total program.

Manage Dependencies = Manage Risks

Estimates are things that are accepted as true, but that may not be true. Activity dependencies and constraints may increase or decrease the impact of project risks. They also influence whether a project remains on schedule, on budget, and within the quality standards. However; they remain assumptions in essence and hence should be regarded are potential risks.

Accordingly, major dependencies are to be included in the project risk log, which will form the basis of the risk management plan. In order to minimize risk to the project and to improve accuracy, dependencies should be determined by experts and people who are actually doing the work, whenever feasible, and be based on the work packages identified in the WBS or the activities within those work packages, as well as their attributes.

Dependencies and constraints should be regularly monitored and assessed in order to manage their impacts on a project’s progress. Project team members may be assigned to monitor specific dependencies. They can also be involved in reviewing the overall schedule for missing dependencies and conflicting assumptions. The collective eye will help generate a much more accurate schedule.


Identifying dependencies determines how the activities relate and puts everything in order. This has a direct impact on schedule and resource management. Since they are in essence logical assumptions, major dependencies may be regarded as potential risks and remain monitored through out the project.