# Precedence diagram method

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{{Short description|Project management technique}}
The '''precedence diagram method (PDM)''' is a tool for [scheduling](/source/Schedule_(project_management)) activities in a [project plan](/source/project_plan). It is a method of constructing a project schedule network diagram that uses boxes, referred to as nodes, to represent activities and connects them with arrows that show the [dependencies](/source/Dependency_(project_management)).  It is also called the activity-on-node (AON) method.
* Critical [tasks](/source/Task_(project_management)), noncritical tasks, and slack time
* Shows the relationship of the tasks to each other
* Allows for what-if, worst-case, best-case and most likely scenario

Key elements include determining predecessors and defining attributes such as 
* early start date
* late start date
* early finish date
* late finish date
* duration
* activity name
* [WBS](/source/Work_breakdown_structure) reference

Slack/[Float](/source/Float_(project_management)): Determines the duration of activity delay that the project can tolerate before the project comes in late. The difference between the earliest and the latest start time.{{sfn|Kerzner|2009}}{{rp|502}}{{sfn|Sanghera|2019}}{{rp|183}} i.e. Slack = latest start date - earliest start day or Slack = latest finish time - earliest finish time.

Any activities which have a slack of 0, they are on the [critical path](/source/Critical_path_method).

thumbnail|right|solving the PDM, with: BS is an early start date. BM is a late start date. KS is an early finish date. KM is a late finish date.

Different Precedence diagram Methods
* [Arrow diagramming method](/source/Arrow_diagramming_method)
* [Project network](/source/Project_network)
* [Critical-path method](/source/Critical-path_method)
* [Gantt chart](/source/Gantt_chart)
* [Program evaluation and review technique](/source/Program_evaluation_and_review_technique)

==References==
{{Reflist}}

== Further reading ==
*{{cite book | author = Kerzner, Harold | year = 2009 | title = Project Management: A Systems Approach to Planning, Scheduling, and Controlling |edition = 10th | publisher = Wiley | isbn = 978-0-470-27870-3| author-link = Harold Kerzner }}
* {{cite book | last = Sanghera| first = Paul | year = 2019| title=PMP in Depth |edition = Third | publisher = Apress | isbn = 978-1-4842-3910-0 | doi=10.1007/978-1-4842-3910-0 | language=en-US}}

==External links==
* [http://www.betterprojects.net/2005/10/pdms-precedence-diagram-method.html Precedence Diagram Method] at Better Projects

{{Authority control}}

Category:Project management techniques
Category:Schedule (project management)

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