Structured analysis and design technique (SADT) is a diagrammatic notation designed specifically to help people describe and understand systems. It offers building blocks to represent entities and activities, and a variety of arrows to relate boxes. These boxes and arrows have an associated informal semantics. SADT can be used as a functional analysis tool of a given process, using successive levels of details. The SADT method not only allows one to define user needs for IT developments, which is often used in the industrial Information Systems, but also to explain and present an activity’s manufacturing processes and procedures.
SADT uses two types of diagrams: activity models and data models. It uses arrows to build these diagrams. The SADT’s representation is the following:
- A main box where the name of the process or the action is specified
- On the left-hand side of this box, incoming arrows: inputs of the action.
- On the upper part, the incoming arrows: data necessary for the action.
- On the bottom of the box, incoming arrows: means used for the action.
- On the right-hand side of the box, outgoing arrows: outputs of the action.
The semantics of arrows for activities:
- Inputs enter from the left and represent data or consumables that are needed by the activity.
- Outputs exit to the right and represent data or products that are produced by the activity.
- Controls enter from the top and represent commands or conditions which influence the execution of an activity but are not consumed.
- Mechanisms identify the means, components or tools used to accomplish the activity. Represents allocation of activities.
The semantics of arrows for data:
- Inputs are activities that produce the data.
- Outputs consume the data.
- Controls influence the internal state of the data.
SADT is used as diagrammatic notation in conceptual design of software engineering and systems engineering to sketch applications, for more detailed structured analysis, for requirements definition, and structured design.