engineering

Structured analysis and design technique

Structured analysis and design technique is a engineering topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Structured analysis and design technique rather than just read about it. In short: Structured analysis and design technique (SADT) is a systems engineering and software engineering methodology for describing systems as a hierarchy of functions. SADT is a structured analysis modelling language, which uses two types of diagrams: activity models and data models.

Key takeaways

Structured analysis and design technique belongs to engineering; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Structured analysis and design technique to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Structured analysis and design technique from memory before moving on to harder problems.

Reference excerpt

Structured analysis and design technique (SADT) is a systems engineering and software engineering methodology for describing systems as a hierarchy of functions. SADT is a structured analysis modelling language, which uses two types of diagrams: activity models and data models. It was developed in the late 1960s by Douglas T. Ross, and was formalized and published as IDEF0 in 1981. It is often contrasted with Object-oriented analysis and design.

Overview 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.

History SADT was developed and field-tested during the period of 1969 to 1973 by Douglas T. Ross and SofTech, Inc. The methodology was used in the MIT Automatic Programming Tool (APT) project. It received extensive use starting in 1973 by the US Air Force Integrated Computer Aided Manufacturing program. According to Levitt (2000) SADT is "part of a series of structured methods, that represent a collection of analysis, design, and programming techniques that were developed in response to the problems facing the software world from the 1960s to the 1980s. In this timeframe most commercial programming was done in COBOL and Fortran, then C and BASIC. There was little guidance on "good" design and programming techniques, and there were no standard techniques for documenting requirements and designs. Systems were getting larger and more complex, and the information system development became harder and harder to do so. As a way to help manage large and complex software. SADT was among a series of similar structured methods, which had emerged since the 1960 such as:

Structured programming in circa 1967 with Edsger W. Dijkstra. Structured design around 1975 with Larry Constantine and Ed Yourdon Structured analysis in circa 1978 with Tom DeMarco, Yourdon, Gane & Sarson, McMenamin & Palmer. Information technology engineering in circa 1990 with James Martin. In 1981 the IDEF0 formalism was published, based on SADT.

SADT topics

Top-down approach The structured analysis and design technique uses a decomposition with the top-down approach. This decomposition is conducted only in the physical domain from an axiomatic design viewpoint.

Diagrams 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.

Roles According to Mylopoulos (2004) in the software development process multiple roles can or should be distinguished:

Author or developer of the SADT models Commenters, who review the author's work Readers or users of the SADT models Experts, who can advise the authors Technical committee or reviewers of the SADT models in detail Project librarian, who govern the project documentation Project manager, who governs the system analysis and design. Monitor or chief analyst to assists SADT developers and users Instructor to train SADT developers and users

Usage 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.

See also IDEF0 Jackson structured programming Structure chart Structured systems analysis and design method Systems analysis

References

Further reading William S. Davis (1992). Tools and Techniques for Structured Systems Analysis and Design. Addison-Wesley. ISBN 0-201-10274-9 Marca, D.A., and C.L. McGowan. (1988). SADT: structured analysis and design technique. McGraw-Hill Book Co., Inc.: New York, NY. Jerry FitzGerald and Ardra F. FitzGerald (1987). Fundamentals of Systems Analysis: Using Structured Analysis and Design Techniques. Wiley. ISBN 0-471-88597-5 David A. Marca and Clement L. McGowan (1988). SADT: Structured Analysis and Design Technique. McGraw-Hill. ISBN 0-07-040235-3 D. Millington (1981). Systems Analysis and Design for Computer Applications. E. Horwood. ISBN 0-85312-249-0 Robertson & Robertson (1999). Mastering the Requirements Process. Addison Wesley. James C. Wetherbe (1984). Systems Analysis and Design: Traditional, Structured, and Advanced Concepts and Techniques. West Pub. Co. ISBN 0-314-77858-6

External links

The IDEF0 method A course about SADT diagrams

Illustrations

Worked examples

Example 1 — a first encounter with Structured analysis and design technique

Start with the simplest possible case. Write down what Structured analysis and design technique claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In engineering, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Structured analysis and design technique before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Structured analysis and design technique ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Structured analysis and design technique

In research: Structured analysis and design technique appears in engineering research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Structured analysis and design technique in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Structured analysis and design technique is common in secondary-school and first-year university syllabi. It links to neighbouring topics Systems analysis, so understanding it makes those chapters shorter.
In everyday life: Look for Structured analysis and design technique outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Structured analysis and design technique in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Structured analysis and design technique means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Structured analysis and design technique out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Structured analysis and design technique in simple terms?

Why does Structured analysis and design technique matter?

Because it connects several engineering ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Structured analysis and design technique?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Structured analysis and design technique.