Format for an influence diagram
An influence diagram represents the main structural features
of a situation and the important relationships that exist among them. It presents
an overview of areas of activity or organizational and other groupings and their
main interrelationships. It is used either to explore those interrelationships,
perhaps leading to a regrouping and redefinition of the system and its components,
or to express a broad view of how things are in the territory you are considering.
Influence diagrams can be developed from a systems map by adding arrows and
can be used as the starting point for a multiple cause diagram by clearer definition
of the type of influence.
- blobs of varying sizes;
- assorted arrows;
- words labelling blobs and possibly also labelling
- key for arrows;
- As in
systems maps, blob lines represent component boundaries. Inclusion of blobs and
a system boundary is optional but highly recommended.
arrow (e.g. 1 or 2 in the figure above) joining component aaa to component bbb or ccc
shows that aaa can or does influence bbb or ccc.
double-headed arrow (e.g. 3) should never be used to denote a two-way
influence unless the influence is identical. Two separate arrows (e.g. 4) are
preferable (see guideline 5).
(e.g. aaa, bbb, ccc, ddd, etc.) label components and system (if shown). They
may also label arrows, if the nature of the influence is not obvious from the
context. Alternatively, different influence can be represented by dotted (e.g.
5) or bold (e.g. 6) lines as long as a key is given.
- Arrows do not show material flows.
- An influence diagram, like a systems map, is a snapshot.
- Arrows denote capacity to influence, not a sequence in time.
- A title defining the system of interest is essential.
using arrows from features in the environment to the system boundary. By
definition factors in the environment affect the system, so such arrows are
superfluous. Arrows from environmental factors should terminate at a specific
system component where possible. Arrows to the system boundary carry
information only if they distinguish different types of influence (see
guideline 3 below).
thicknesses of lines can indicate different strengths of influence. Thus in
the figure above, 6 denotes a stronger influence than 1.
- It is
possible to distinguish different types of influence (e.g. influence via
finance, information, supply of materials). Do so only if such distinctions are
important and not self-evident, by the use of different lines (colour, dashing)
to show this, and a key to explain them.
the temptation to overload the diagram with information. It may be helpful to
you to put down all influences you can think of at first, but for communication
to others, select the significant ones.
the temptation to use double headed arrows. Use them only when the influence is
truly reciprocal and of the same type. If you are not careful the use of a
double headed arrow can obscure important differences in the types of influence
and their magnitude, which is seldom, if ever, equal. Use two arrows pointing
in opposite directions instead.
and relative distance can also be used to suggest things about the nature of
the relationships shown, e.g. an important but remote relationship.