structure design in software engineering - Csmates.com

structure design in software engineering

structure design

The structured design was proposed by many creators like Stevens, Myers, and Constantine to provide means for dealing with the complexity that was overwhelming developers as programs grew larger. These ideas were immediately popular and the approach was extended to analysis.

Aim of Structured Design

The aim of the structured design is to specify modules that can be developed, written, tested, modified, and reuse independently, and combined to form the final program. Good Modularisation is thus a primary goal.

Module quality depends mainly on two factors:
  • Coupling
  • Cohesion

Coupling is the strength of interconnection between pairs of modules. Good modules are as loosely coupled to other modules as possible. 

Cohesion is how tightly bound or related a module's actions are to one another. Good modules have high cohesion.

Tools for structured design.

Key tools that are used for structured design.

  • Structure Charts.
  • Modules Identification and Specification Techniques
Structure Charts
The central theme in SASD is the concept of the "black-box" i.e. a system is broken down, decomposed, or otherwise partitioned into well-defined processing modules.

A structure chart is a graphical representation of the program's organization. Flowcharts illustrate how the program will create the desired output.

A structured chart is used to show the programmers of a system how the system is partitioned into modules, what the modules calling organization is, and identify the parameters or information passes between modules.

This modularized view means that the structure chart is used more to identify the "external functions, inputs, and outputs of modules rather than their internal procedures and data." 

A structure chart shows what tasks the program must perform, while the flowchart shows how the program will perform these tasks.

The development of the structure chart must precede the development of the flowchart.

structural design program

Structure chart of a simple program having mainly three steps, namely, initialization, process, and End-of-Job.

Modules Identification and Specification Techniques

When developing the implementation model, and specifically the structure charts, arguably the largest task is the identification and specification of the modules within the system. As with most methodologies and techniques, there are a few guidelines to be used when developing individual modules as well as when considering the relationship between modules.

Module Specification Methods
 Several methods can be used to specify a module. Two possible methods are:
  • Interface/Fucntional
  • Pseudocode
This specification provides a good balance of specification details and is in line with the "black box" spirit of SASD. The interface, or rather, the input and output of the module, provides the detail of what the module needs and produces, while the functional specification provides good documentation as to what, exactly, the module is supposed to do.

Pseudocode is not a programming language. It is a mixture of English, mathematics, and programming constructs, formatted so that a human can easily determine what is going on.

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