Introduction to Activity Networks

Activity Networks: These are visual representations used to organise and manage complex projects encompassing multiple activities. Each node or vertex within the network represents a distinct task/activity.
Dependencies: These are relationships between tasks that dictate the order in which activities must be completed. Dependent tasks must be completed in the correct sequence.
Critical path: This is the longest path from start to finish in the network, identifying the key activities which must be completed on time to meet the project deadline.

Structure of Activity Networks

Arcs: These represent the activities to be undertaken in a project. The duration of each activity is represented by the weight on its arc.
Nodes: Nodes in the network can represent several things, such as points in time (like the start or finish of an activity). Nodes can also denote events within the project.
Dummy activities: These are activities with zero duration that are added to maintain the dependencies between tasks. They are often necessary when completing complex activity network diagrams.

Earliest Start Time (EST) and Latest Finish Time (LFT): These are important calculations in project management. EST is calculated by moving from the start towards the end of the network, and LFT is calculated by moving from the end towards the start.
Total Float: This specifies the amount of time that you can delay a task without delaying the project. More slack or total float means that the project schedule is more flexible.