Live Network Diagram
About this app
Forward and backward pass run as a wave through the network of project Lumen, in sync with the Gantt chart. Change durations and see when float runs out and the critical path jumps.
With explain mode: an AI tutor walks you through the app, points out what matters in the scene and answers your questions.
Forward and backward pass
Network scheduling computes the earliest and latest start and finish of each activity from durations and dependencies. The forward pass gives early start and early finish: an activity starts once its last predecessor is done. The backward pass works from the project end and gives late start and late finish. The difference is the total float. Activities with zero float form the critical path, so any delay there moves the project end. Activities with float may slip until the float is used up.
What the app shows
The case project Lumen (fictional) has ten activities A to J with durations of three to nine weeks. The calculation runs through the network as a wave. The project ends in week 28, the critical path is A-B-E-F-G-H-I, and the float is two weeks for C, four for D and two for J. A list shows all six paths with their length. The network and the Gantt chart can be shown separately or together, and a line marks the trade fair in week 30.
Things to try
Extend activity D by five weeks and watch its four weeks of float run out while the critical path jumps to A-D-G-H-I. Delay C by two and D by four weeks: now three paths are equally long and no single activity is critical. Shorten activity E by three weeks and check whether the project really ends earlier. This shows why speeding up only helps on the critical path.
Frequently asked questions
- What is the critical path?
- The critical path is the longest chain of dependent activities from project start to project end. Its activities have no total float. A delay on this path moves the project end by the same amount. A network can have several critical paths.
- How is total float calculated?
- Total float is the difference between late start and early start, or between late finish and early finish. It states how many time units an activity may slip without moving the project end.
- Why does speeding up an activity with float not help?
- The longest chain sets the project end. An activity with float lies on a shorter path. If it gets faster, only its float grows and the end stays the same. Crashing makes sense on the critical path, until a second path becomes equally long.
- What does the app model?
- The app uses an invented case project with ten activities, simple finish-to-start relations and durations in weeks. Lags, overlaps and resource limits are not modelled. The calculation follows the classic critical path method.
Subject: Projektmanagement
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