How To Draw Aoa Network Diagram

What is an Arrow Diagram?

Quality Glossary Definition: Arrow diagram

Also called: activity on pointer diagram, action network diagram, network diagram, activity chart, node diagram, CPM (critical path method) chart

Variation: PERT (program evaluation and review technique) chart

An arrow diagram is divers every bit a process diagramming tool used to make up one's mind optimal sequence of events, and their interconnectivity. It is used for scheduling and to make up one's mind the critical path through nodes. The arrow diagramming method shows the required order of tasks in a project or process, the best schedule for the entire project, and potential scheduling and resources issues and their solutions. The arrow diagram lets you calculate the "disquisitional path" of the projection—the menses of critical steps where delays tin bear upon the timing of the entire project and where addition of resource can speed upward the project.

When to Use an Arrow Diagram

When scheduling and monitoring tasks within a complex project or process with interrelated tasks and resources
When you know the steps of the projection or procedure, their sequence, and how long each pace takes
When project schedule is critical, with serious consequences for completing the project belatedly or significant advantage to completing the project early on

Arrow Diagram Process

Materials needed: Sticky notes or cards, marking pens, and large writing surface (newsprint or flipchart pages).

Drawing the Network

List all the necessary tasks in the projection or process. 1 method is to write each task on the elevation half of a card or pasty note. Across the middle of the card, depict a horizontal arrow pointing correct.
Determine the correct sequence of the tasks. Practice this by request three questions for each task:
- Which tasks must happen before this one tin begin?
- Which tasks tin can be washed at the aforementioned fourth dimension equally this 1?
- Which tasks should happen immediately later this ane?
  Tip: Create a table with 4 columns: prior tasks, this task, simultaneous tasks, following tasks for ease of utilize.
Diagram the network of tasks. If you are using notes or cards, suit them in sequence on a large piece of paper. Time should flow from left to right and concurrent tasks should be vertically aligned. Exit space between the cards.
Betwixt each two tasks, draw circles for "events." An upshot marks the outset or end of a job and can help visually divide tasks.
Wait for the three common problem situations below and redraw them using "dummies" (not real tasks) or actress events. A dummy is an pointer drawn with dotted lines used to separate tasks that would otherwise start and cease with the aforementioned events or to bear witness logical sequence.
- 2 simultaneous tasks start and end at the same events.
  - Solution: Use a dummy and an actress upshot to dissever them. In Effigy i, event 2 and the dummy betwixt 2 and 3 take been added to separate tasks A and B.
- Task C cannot start until both tasks A and B are complete; a fourth job, D, cannot start until A is consummate, but need not look for B. (See Effigy ii.)
  - Solution: Utilise a dummy between the stop of task A and the offset of task C.
- A second task tin can be started before part of a kickoff task is done.
  - Solution: Add an actress event where the 2d task can brainstorm and utilize multiple arrows to break the first task into two subtasks. In Figure 3, event 2 was added, splitting task A.
    Effigy 1: Dummy separating simultaneous tasks
    
    Figure 2: Dummy keeping sequence correct
    
    Effigy iii: Using an extra event
When the network is correct, label all events in sequence with event numbers in the circles. It may exist helpful to label all tasks in sequence, using letters.

Scheduling: Disquisitional Path Method (CPM)

Determine task times—the best approximate of the time that each job should crave. Utilise one measuring unit (hours, days, or weeks) throughout, for consistency. Write the fourth dimension on each task'southward arrow.
Determine the "critical path," the longest path from the beginning to the cease of the project. Marker the critical path with a heavy line or color. Summate the length of the critical path(the sum of all the task times on the path).
Calculate the earliest times each task tin can first and finish, based on how long preceding tasks take. These are called earliest outset (ES) and earliest terminate (EF). Commencement with the first task, where ES = 0, and work forward. Describe a foursquare divided into four quadrants, as in Figure 4. Write the ES in the elevation left box and the EF in the height correct.
For each chore:
- Earliest start (ES): the largest EF of the tasks leading into this one
- Earliest end (EF): ES + job fourth dimension for this task
Effigy iv: Pointer diagram fourth dimension box

ES Earliest starting time

EF Earliest terminate

LS Latest start

LF Latest finish
Summate the latest times each task can kickoff and finish without upsetting the project schedule, based on how long later on tasks volition take. These are called latest start (LS) and latest stop (LF). Outset from the last task, where the latest terminate is the project borderline, and work backwards. Write the LS in the lower left box and the LF in the lower right box.
- Latest end (LF): the smallest LS of all tasks immediately following this one
- Latest start (LS): LF – task fourth dimension for this task
Calculate slack times for each task and for the entire project.
Full slack is the time a chore could be postponed without delaying the project schedule.

Total slack: LS -ES = LF -EF

Costless slack is the time a task could be postponed without affecting the early offset of any chore following it.

Gratuitous slack: the earliest ES of all tasks immediately post-obit this one - EF