Types of diagrams

Diagrams are a fundamental part of communication.

This section covers some common types of diagrams:


Flowcharts show a sequence of steps and decisions for a process, generally linked by  lines or arrows. The aim of a flowchart is to show a process from beginning to end:

Structure of a flowchart

Different types of steps in the process may have a particular shape. Straight paths or arrows are used for direct connections or labelling, and elliptical lines or arrows are used for cycles. Diamonds represent decision points, and dotted lines indicate optional paths:

Rather than drawing these shapes manually, flowcharts are typically created using chart or diagramming software.

There are many forms of flowcharts, including decision trees, workflow diagrams, process maps, swimlane diagrams and dataflow diagrams.

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Relation diagrams

Relation diagrams show connections between items such as areas, factors, issues or processes. Connecting lines between the shapes indicate the relationship. Arrows are often used to represent how one item has an effect on another (see example below).

Relation diagrams help to show cause-and-effect relationships. They are best used when trying to analyse and communicate links between things.

Types of relation diagrams include comparison diagrams, conceptual diagrams, fishbone diagrams, cycle diagrams and cladograms.

Figure 3  Relationship between components of the Tasmanian Pesticides Impact Rating Index

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Venn diagrams

Areas of similarity and difference between items are best depicted by a venn diagram (see example below). The diagram consists of overlapping shapes, usually circles. Common characteristics of items are shown where the shapes overlap.

Forms of venn diagram include discrete sets (where sets are different), and set and subset (where one is a subset of the other).

Figure 3  Elements of sustainable development
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A timeline diagram is very effective for showing events in chronological order. It consists of a horizontal bar representing time, which is marked with event items to indicate when the events happened or will happen (see example below).

It is important to identify the most appropriate segment of time to be illustrated from beginning to end. Long periods of no activity can be depicted by a gap or zigzag. However, too many gaps in the scale of the timeline will make it difficult for readers to understand.

Source: Data sourced from Wikipedia (2015), List of introduced species.

Figure 3  Timeline of the arrival of selected feral animals in Australia from 1750 to 1950

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Illustrative diagrams

Illustrative diagrams may use drawings, 3D modelling, symbols or graphical illustration techniques to communicate complex or essential attributes of a system (also see Illustrations). This type of diagram helps to clarify concepts, show relationships and processes, and synthesise key messages (see example below).

Illustrative diagrams are very useful in depicting aspects of a system by:

  • labelling the components
  • changing the scale of the components to make them easy to see
  • showing where the components are located within the system
  • showing how something works, moves or changes.

Source: Adapted from Department of Industry (2013). Your home: Australia’s guide to environmentally sustainable homes, 5th edn.

Figure 3  Turbulence extends upwards up to 2 times the height of an obstacle and 20 times downwind: turbine sweep area must be clear of turbulence

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