Network diagrams, crucial for project management and planning, follow specific rules to ensure clarity and accurate representation of project activities. The primary rules focus on logical flow, avoiding ambiguity, and ensuring all activities are correctly linked.
Key Rules for Drawing Network Diagrams:
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Avoid Arrow Crossings: Minimize the crossing of arrows representing activities. If crossings are unavoidable, use bridging techniques (small curves in one arrow) to clearly show that the activities don't intersect. This enhances readability.
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Events Define Activities: Every activity must be bounded by two events: a start event and an end event. This means each activity begins at one event and ends at another, clearly defining its place in the sequence.
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No Dangling Events: Every event in the network must be connected to at least one activity. An event should not "hang loosely" without leading to any subsequent activities or arising from any prior activities (except possibly the very first and very last events in the project).
Additional Considerations:
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Uniqueness of Activity Representation: Each activity is represented by one, and only one, arrow in the network diagram.
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Logical Sequence: Arrows generally flow from left to right, indicating the progression of time and activity sequence. This helps to visually represent the project timeline.
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Consistent Direction: While the diagram as a whole may snake or curl for legibility, the activities within must flow in a consistent direction of time. Avoid activities with arrows pointing backwards.
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Minimize Loops: Aim to design a diagram where loops are not present. Circular dependencies indicate logical errors in the project plan.
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Start and End Events: The network usually has one start event (representing the project beginning) and one end event (representing project completion). If a project has multiple starting or ending points, these can be represented, but strive for a single terminal point if possible.
Following these rules leads to a network diagram that accurately reflects the project plan, facilitates communication, and enables effective scheduling and resource allocation.
