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6.2 Activity Sequencing


Activity sequencing involves identifying and documenting interactivity dependencies. Activities must be sequenced accurately in order to support later development of a realistic and achievable schedule.


6.2.1 Inputs

  1. Activity list
  2. Product description
  3. Mandatory dependencies
  4. Discretionary dependencies
  5. External dependencies
  6. Constraints
  7. Assumptions

6.2.2 Tools & Techniques

  1. Precedence diagramming method
  2. Arrow diagramming method
  3. Conditional diagramming method
  4. Network templates

6.2.3 Outputs

  1. Project network diagram
  2. Activity list updates






6.2.1 Activity Sequencing - Inputs Activity list

Refer to Activity list. Product description

Product characteristics often affect activity sequencing (eg the physical layout of the plant to be constructed) and should be reviewed for accuracy. Refer to Product description. Mandatory dependencies

Mandatory dependencies are those which are inherent in the nature of the work being done. They often involve physical limitations and are also called hard logic. Discretionary dependencies

Discretionary dependencies are those which are defined by the project management team. They are usually defined based on knowledge of:

They are also called preferred logic, preferential logic or soft logic. External dependencies

These involve a relationship between project activities and non-project activities. For example, the testing activity in a software project may be dependent on delivery of hardware from an external source.

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6.2.2 Activity Sequencing - Tools and Techniques Precedence diagramming method(PDM)

This is a method for constructing a project network diagram using nodes to represent the activities and connecting them with arrows that show dependencies. This technique is also called activity-on-node (AON) and is usd by most software packages.

It uses four types of dependencies:

  1. Finish-to-start
  2. Finish-to-finish
  3. Start-to-start
  4. Start-to-finish Arrow diagramming method (ADM)

This is a method of constructing a project network diagram using arrows to represent the activities and connecting them at the nodes to show the dependencies. This technique is also known as activity-on-arrow.

It only uses finish-to-start dependencies and may require use of dummy activities to define all logical relationships correctly. Conditional diagramming methods

Diagramming techniques such as GERT (Graphical Evaluation and Review Technique) and System Dynamics models allow for non-sequential activities such as loops. Neither PDM or ADM allow loops or conditional branches. Network templates

Standardized networks can be used to expedite the preparation of project network diagrams.

Portions of a network are often called subnets or fragnets.


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6.2.3 Activity Sequencing - Outputs Project network diagram

A project network diagram is a schematic display of the project's activities and the logical relationships among them. This is different from PERT (Program Evaluation and Review Technique) which is a specific type of project network diagram seldom used today. Activity list updates

Preparation of a project network diagram may reveal instances where an activity must be divided or otherwise redefined to diagram the correct logical relationships.


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