The layout is one of the most important visual attributes of a model. A good layout
is perceived instantly and almost unconsciously. An unclear, cluttered layout is
distracting and hinders perception of more detailed information. Putting the objects
in a diagram in a pattern that is easily recognisable and fitting to the underlying
message is a great aid to the viewer of the diagram. It very much helps in discerning
and remembering which objects there are and which relationships are relevant.
Layout aspects of a diagram include: basic pattern, horizontal and vertical alignment,
above/before positioning, symmetry, distance of objects from the centre and
from other objects, distribution of white space, distribution of connectors, density
of objects and connectors. A basic pattern makes clear to the viewer what strategy is
being followed in positioning objects and what meaning can be derived from the
position of an object. For instance, in a workflow diagram the activities might be
positioned from left to right in the order of execution and having the same vertical
position can mean being executed in the same stage of the process.