SADT Diagram Conventions Lay out and number boxes on

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					SADT/IDEF0 Diagram
Conventions

Lay out and number boxes on each diagram
from upper left to lower right. The resulting
pattern suggests a dominance among the
diagram boxes. Write the C-number of the
diagram that decomposes the box below the
lower right hand corner.




All arrows should be drawn along horizontal and
vertical axes. Boxes always have control arrows
but they may or may not have input arrows.
Control arrows constrain and trigger functions.
Without controls, a system cannot function.




Feedback loops to the same box should most
likely be depicted within the decomposed box
rather than at the higher level.




IDemonstrating manner in which output of a box
provides controls for a subsequent process.




J. Heim, Industrial Engineering, University of Washington   page-1
Maximize the distance between boxes and arrow
corners, and between arrow and box
intersections. More white space means easier
reading of the diagram. The arrangement of
arrows connecting boxes should allow the reader
to easily follow each path.




Maximize space between parallel arrows. This
provides room for appropriate labels and helps
the reader distinguish the actual number of
arrows as well as following the arrow paths.




Join open-ended arrows when they represent the
same data. This illustrates in a graphic manner a
single source of similar data items.




Bundle arrows with the same source or
destination if the data is related. You should
develop an aggregate name for the data bundle
to better describe the nature of the data.




J. Heim, Industrial Engineering, University of Washington   page-2
Control feedbacks are drawn “up and over.”
This correctly shows constraint feedback with
minimal crossover of lines and tends to force all
control arrows into the upper right-hand region
of the diagram.




Input feedbacks are drawn “down and under.”
This correctly shows reverse dataflow with the
minimum number of crossovers, and tends to
force all input arrows into the lower left-hand
region of the diagram.




Connect arrows that touch several boxes at the
same relative ICOM (Input, Control, Output,
Mechanism) position whenever possible. This
consistency will simplify the reading and
interpretation of the diagram.




Avoid unnecessary arrow crossings when
interconnecting several boxes on a diagram.
While the simplest and most obvious rule, it
probably has the most influence on reducing
diagram complexity.




J. Heim, Industrial Engineering, University of Washington   page-3
Minimize the number of curves and corners for
each arrow–they should be as clean and direct as
possible to reduce complexity.




J. Heim, Industrial Engineering, University of Washington   page-4

				
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