A schedule or diagram is a converted version of the project action plan into an operational timetable in which every stakeholder can work from. It is a powerful tool to managing the project as it charts out the plan, budget, check pints and controls of the overall project. The schedule is a working diagram which is created from the various documents that contribute to the overall project planning phases. For instance, the responsibility matrix, the scope statement, and project charter. Scheduling enables the development of the WBS whilst providing additional clarity and understanding around the works to be completed.
Project scheduling is a system used to link specific activities to their event relationships. It charts the relationship between the tasks that must precede or follow other tasks for the project to complete successfully. It clearly defines the required tasks (according to type and time required to complete) so that the critical path can be identified.
There are two techniques that can be used either singularly or combined to map this network diagram.
Program Evaluation and Review Technique (PERT)
Critical Path Method (CPM)
The below elements are identified, defined, and used to create these networks.
There are two types of Network Diagrams:
Activity-on-Arrow (AOA)
This diagram reflects the finish to start dependencies between activities. On the diagram the activities are represented by arrows in which they are connected by nodes, back of arrow indicating the start of the activity. The arrow length indicates the duration of each activity (Lopez, 2014)
@projectmanager.com
Activity-on-Nodes (AON)
This diagram reflects all four dependencies (finish to start, start to start, finish to finish, start to finish). On the diagram the activities are represented by nodes and then each node is connected to each other by arrows. The arrows reflect the relationship between activities.
@projectmanager.com
The Critical Path Method (CPM) is used to keep project on track, and this is generated out of either one of the network diagrams. The Critical Path method uses four main elements:
Critical Path Analysis
Float Determination
Early Start & Early Finish Calculation
Late Start & Late Finish Calculation
The critical path can:
Identify activities that must be completed on time so that the whole project is completed on time
Provides an insight into which tasks can be delayed and for how long so that they don’t impact the whole project
Calculate the minimum amount of time it will take to complete the project
Calculates the earliest and latest dates that each activity can start (PROJECT-MANAGEMENT-SKILLS.COM (2010-2021)
The critical path is highlighted in the below diagram by the red line
@(PROJECT-MANAGEMENT-SKILLS.COM (2010-2021)
Float Determination
The float (which is the amount of time an activity can be delayed before it causes the whole project to be delayed) can then be determined once the critical path has been established. The float is based on the longest path.
The critical path is indicated by the red line in the below diagram.
@PROJECT-MANAGEMENT-SKILLS.COM (2010-2021)
Forward and Backward Pass
According to Tiemchart 2021, “Forward pass is a technique to move forward through network diagram to determining project duration and finding the critical path or Free Float of the project. Whereas backward pass represents moving backward to the end result to calculate late start or to find if there is any slack in the activity”.
In the below video, the forward and backward pass methods are described.
References
Lopez, A, (2021). Arrow Diagrams for Projects: Activity on Node & Activity on Arrow. URL: Arrow Diagrams for Projects: Activity on Node & Activity on Arrow (projectmanager.com) [Accessed on 12.11.2021]
Project Management Skills, (2021). The Critical Path Method (CPM). URL: The Critical Path Method (CPM) | Critical Path Analysis Examples (project-management-skills.com) [Accessed on 12.11.2021]
Tiemchart, (2021). Forward Pass and Backward Pass in Project Scheduling. URL: Forward pass and backward pass in project scheduling | Early Start (ES) (tiemchart.com) [Accessed on 12.11.2021]
Hi Kerry, your post about project scheduling is very well describing the whole process. I like especially the graphy you used for clarifying Acitivity on Node and Arrow. Best wishes, Michaela.