Sadt - AbsoluteAstronomy.com

Structured Analysis and Design Technique (SADT) is a software engineering methodology for describing system

System

System is a set of interacting or interdependent components forming an integrated whole....

s as a hierarchy of functions.

Overview

Structured Analysis and Design Technique (SADT) is a diagram

Diagram

A diagram is a two-dimensional geometric symbolic representation of information according to some visualization technique. Sometimes, the technique uses a three-dimensional visualization which is then projected onto the two-dimensional surface...

matic notation designed specifically to help people describe and understand system

System

System is a set of interacting or interdependent components forming an integrated whole....

s. 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

Semantics

Semantics is the study of meaning. It focuses on the relation between signifiers, such as words, phrases, signs and symbols, and what they stand for, their denotata....

. SADT can be used as a functional analysis tool of a given process, using successive levels of details. The SADT method allows to define user needs for IT developments, which is very used in the industrial Information Systems, but also to explain and to present an activity’s manufacturing processes, procedures.

The SADT supplies a specific functional view of any enterprise by describing the functions and their relationships in a company. These functions fulfill the objectives of a company, such as sales, order planning, product design, part manufacturing, and human resource management. The SADT can depict simple functional relationships here and can reflect data and control flow relationships between different functions.

History

SADT has been developed and field-tested during the period of 1969 to 1973 by Douglas T. Ross

Douglas T. Ross

Douglas Taylor Ross was an American computer scientist pioneer, and Chairman of SofTech, Inc.. He is most famous for originating the term CAD for computer-aided design, and is consider to be the father of Automatically Programmed Tools a language to drive numerically controlled manufacturing.-...

and SofTech, Inc.

SofTech, Inc.

SofTech, Inc., , developer of ProductCenter, the company's PDM/PLM solution. WTC was one of the earliest PDM/PLM providers in the industry, having delivered PLM software products beginning with its first software product CMS in the early 1990s, along with many technology firsts, including the...

. 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) "it 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

COBOL

COBOL is one of the oldest programming languages. Its name is an acronym for COmmon Business-Oriented Language, defining its primary domain in business, finance, and administrative systems for companies and governments....

and Fortran

Fortran

Fortran is a general-purpose, procedural, imperative programming language that is especially suited to numeric computation and scientific computing...

, then C

C (programming language)

C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....

and BASIC

BASIC

BASIC is a family of general-purpose, high-level programming languages whose design philosophy emphasizes ease of use - the name is an acronym from Beginner's All-purpose Symbolic Instruction Code....

. There was little guidance on “good” design and programming techniques, and there were no standard techniques for documenting requirements and designs. Systems where 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. Since the end 1960 multiple Structured Methods emerged".

Structured programming
Structured programming
Structured programming is a programming paradigm aimed on improving the clarity, quality, and development time of a computer program by making extensive use of subroutines, block structures and for and while loops - in contrast to using simple tests and jumps such as the goto statement which could...

in circa 1967 with Edsger W. Dijkstra.
Structured Design around 1975 with Larry Constantine
Larry Constantine
Larry LeRoy Constantine is an American software engineer and professor in the Mathematics and Engineering Department at the University of Madeira Portugal, who is considered one of the pioneers of computing...

and Ed Yourdon
Structured Analysis
Structured analysis
Structured Analysis in software engineering and its allied technique, Structured Design , are methods for analyzing and converting business requirements into specifications and ultimately, computer programs, hardware configurations and related manual procedures.Structured analysis and design...

in circa 1978 with Tom DeMarco
Tom DeMarco
Tom DeMarco is an American software engineer, author, teacher and speaker on software engineering topics. He is known as one of the developers of Structured analysis in the 1980s.- Biography :...

, Yourdon, Gane & Sarson, McMenamin & Palmer.
Information Engineering
Information engineering
Information engineering or information engineering methodology in software engineering is an approach to designing and developing information systems.-Overview:...

in circa 1990 with James Martin
James Martin (author)
James Martin is a British Information Technology consultant and author, who was nominated for a Pulitzer prize for his book, The Wired Society: A Challenge for Tomorrow .- Biography :...

.

In 1981 the IDEF0

IDEF0

IDEF0 is a function modeling methodology for describing manufacturing functions, which offers a functional modeling language for the analysis, development, reengineering, and integration of information systems; business processes; or software engineering analysis.IDEF0 is part of the IDEF family...

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

Top-down and bottom-up design

Top–down and bottom–up are strategies of information processing and knowledge ordering, mostly involving software, but also other humanistic and scientific theories . In practice, they can be seen as a style of thinking and teaching...

. This decomposition is conducted only in the physical domain from an axiomatic design viewpoint. Because of this nonzigzagging process, there is no guarantee of functionality or productivity. Therefore, those methods faded away as the requirements for software systems increased and the object-oriented method was introduced.

Diagrams

SADT uses two types of diagrams: activity models and data model

Data model

A data model in software engineering is an abstract model, that documents and organizes the business data for communication between team members and is used as a plan for developing applications, specifically how data is stored and accessed....

s. 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 from the right and represent data or products that are produced by the activity.
Controls enter from the top and represent commands 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.

External links

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