Sequencing activities in a work breakdown structure (WBS) involves identifying and documenting relationships among them, including task dependencies and which ones should have priority. These relationships are logical and are known as ‘network logic’. The key deliverable from this sequencing is a network diagram, also called a ‘network chart’.
The benefit of defining the logical sequence of work is to achieve the greatest efficiency for the work within the project’s constraints.
By the end of this topic, you will understand:
- Network logic (types of activity relationships)
- Types of activity dependencies
- Dependency Logs
- Network diagram.
Sequencing activities is the first step toward developing a project schedule.
Sequencing activities begin with deciding on the method or software to use. Many project managers use sticky notes to begin this process and then use software to create the network diagram. (We looked at project management software in section 2.3.)
Input is needed from key team members and relevant experts who have experience with the work involved.
Watch
Watch the following video to learn about the process of sequencing activities:
‘Drawn Out Project Management: Sequence Activities Process’ by The Crowd Training on YouTube.
The set of relationships between activities is called ‘network logic’. Within a WBS, some activities depend on others and cannot start until those activities are finished. Some activities can start together and finish together.
Relationships between activities are known as ‘dependencies’. These can vary with the nature of the work and the industry. However, there are four relationship (or dependency) types that are commonly used:
- Finish to start (FS)
- Finish to finish (FF)
- Start to start (SS)
- Start to finish (SF)
Resource
These relationships are described in the following article:
Types of Tasks
When you have defined the type of relationship or dependency (also called network logic) between two activities, you can then define the type of each task involved in a relationship.
There are two commonly used types of tasks:
- Predecessor task – A task that comes before another task.
- Successor task – A task that comes after another task.
Lag and Lead Time
Some related tasks need a time gap between them, or they can overlap.
- Lag time – is a required delay between two tasks with a dependency. For example, if you need to paint a window (predecessor task) and hang blinds (successor task), you may need to wait one day for the paint to dry (the lag time) before you can install the blinds.
- Lead time – is the overlapping time between tasks with a dependency. For example, a successor task can begin anytime after its predecessor task has started. Still, you will need to calculate or estimate a lead time for the successor task and enter this lead time as a negative value in the schedule.
For painting a window and hanging blinds, painting the window is the predecessor task and hanging the blinds is the successor task, with one day’s lag time in between. It is also a ‘finish-to-start’ task.
There are four types of dependencies found in projects:
| Type | Description |
|---|---|
| Mandatory | Required due to the nature of the work or an area of compliance, for example, checking equipment and completing documentation before starting a task to meet safety requirements |
| Optional or discretionary | Tasks that are scheduled based on industry best practice or an organisation’s preference, for example, doing plumbing and electrical work separately instead of in parallel |
| External | Tasks that have involvement with parties, events, etc. external to the project or business, for example, having to wait for a supplier to send raw materials |
| Internal |
|
Watch
Watch the following video to learn about external dependencies:
‘What Are External Dependencies in Your Project?’ by Online PM Courses - Mike Clayton on YouTube.
Watch
Watch the following video to learn more about task dependencies:
‘What are Task Dependencies in Project Management?’ by Online PM Courses - Mike Clayton on YouTube.
Dependency log
Dependencies should be documented in a log, which can be created using word processing software or a tool within project management software.
A dependency log may include the following for each dependency:
- Unique identification reference.
- Dependency description.
- Project or subproject name.
- Task description.
- Delivery date of dependency.
- Probability of dependency not being completed on time.
- Impact of dependency not being completed on time.
- Status of dependency, which is updated as the project progresses.
- Owner of the dependency.
- Date raised.
As project manager, you may hold a dependency awareness workshop, where all key stakeholders, team members and relevant experts are brought together to walk through the proposed project to identify the dependencies.
The project manager's recording, monitoring and managing dependencies are critical duties. If they are not appropriately managed, dependencies can cause project failure.
Resource
Learn more about dependencies and how to handle them at the following links:
‘How to Handle Dependencies in Your Projects’ from BrightWork
‘The Ultimate Guide to Project Dependencies and Constraints’ from Rebel’s Guide to PM
The most popular method for sequencing activities is the precedence diagramming method (PDM). The outcome of this method is a network diagram, also known as a ‘project schedule network diagram’ or ‘network chart’.
A network diagram shows the sequence of activities required from the start to the end of a project. Some may be sequenced in parallel or with overlap. Boxes or nodes describe the activities, and arrows show their relationships.
Developing a network diagram will help you to:
- Visually represent the project’s progress for stakeholders
- Establish project workflows
- Track dependencies and potential bottlenecks as the work progresses.
Resource
Read the following article to see an example of a network diagram and its breakdown:
‘How to Sequence Activities in a Project? A Handy Guide’ from Master of Project Academy
The precedence diagramming method (PDM) is also called activity-on-node (AON) because of the boxes/ nodes and arrows used.
A network diagram is an important input for determining the critical path of a project, especially if activity durations are added to the activity nodes/boxes in the diagram.
Watch
Watch the following video about sequencing activities. The video shows how activities are sequenced and how a network diagram can be created using sticky notes:
‘Sequence Activities Demonstration’ by Andy Kaufman on YouTube.
Other tools and methods for developing network diagrams include the arrow diagramming method (ADM) and the Graphical Evaluation and Review Technique (GERT). However, the most commonly used method is PDM.
Resource
Learn about ADM and PDM by reading the following article:
‘What Is a Network Diagram in Project Management?’ from Wrike
Activity 3A: Sequencing activities for FF
Case study
Families First Relocation Project – Part 3
You are now ready to sequence the activities you identified and documented earlier in the WBS for this project. The Families First (FF) administration manager has given you contact details for the removal company hired for this work. The removal company agrees that, if needed, separate crews and trucks could pack and transport furniture, equipment, etc., from all four sites in parallel. However, FF would need to confirm this request as quickly as possible to ensure crew/truck assignments.
You discuss this parallel packing/transport plan with the FF director. She tells you that because their counselling service is a crisis service, a minimum group of three counsellors must be on duty at each of the two branches at all times. During the move, three counsellors will be rostered at the main office – but one of the new locations must be open and working also. This means the packing and transport will need to be staggered.
Read the case study ‘Families First Relocation Project – Part 3’ and determine the relationships and dependencies for the tasks in the WBS to allow for the FF director’s requirements.
In a separate document or on a piece of paper, develop a network diagram to discuss with the FF director and administration manager.
Activity 3B: Sequencing activities for your project
Review your previously developed WBS and identify the types of activity relationships and activity dependencies required for your project.
In a separate document or on a piece of paper, develop a network diagram for the execution of your project.
