Software process designing concepts

Introduction to design process

  • The main aim of design engineering is to generate a model which shows firmness, delight and commodity.
  • Software design is an iterative process through which requirements are translated into the blueprint for building the software.

Software quality guidelines

  • A design is generated using the recognizable architectural styles and compose a good design characteristic of components and it is implemented in evolutionary manner for testing.
  • A design of the software must be modular i.e the software must be logically partitioned into elements.
  • In design, the representation of data , architecture, interface and components should be distinct.
  • A design must carry appropriate data structure and recognizable data patterns.
  • Design components must show the independent functional characteristic.
  • A design creates an interface that reduce the complexity of connections between the components.
  • A design must be derived using the repeatable method.
  • The notations should be use in design which can effectively communicates its meaning.

Quality attributes

The attributes of design name as 'FURPS' are as follows:

Functionality:
It evaluates the feature set and capabilities of the program.

Usability:
It is accessed by considering the factors such as human factor, overall aesthetics, consistency and documentation.

Reliability:
It is evaluated by measuring parameters like frequency and security of failure, output result accuracy, the mean-time-to-failure(MTTF), recovery from failure and the the program predictability.

Performance:
It is measured by considering processing speed, response time, resource consumption, throughput and efficiency.

Supportability:
  • It combines the ability to extend the program, adaptability, serviceability. These three term defines the maintainability.
  • Testability, compatibility and configurability are the terms using which a system can be easily installed and found the problem easily.
  • Supportability also consists of more attributes such as compatibility, extensibility, fault tolerance, modularity, reusability, robustness, security, portability, scalability.

Design concepts

The set of fundamental software design concepts are as follows:

1. Abstraction
  • A solution is stated in large terms using the language of the problem environment at the highest level abstraction.
  • The lower level of abstraction provides a more detail description of the solution.
  • A sequence of instruction that contain a specific and limited function refers in a procedural abstraction.
  • A collection of data that describes a data object is a data abstraction.
2. Architecture
  • The complete structure of the software is known as software architecture.
  • Structure provides conceptual integrity for a system in a number of ways.
  • The architecture is the structure of program modules where they interact with each other in a specialized way.
  • The components use the structure of data.
  • The aim of the software design is to obtain an architectural framework of a system.
  • The more detailed design activities are conducted from the framework.
3. Patterns
A design pattern describes a design structure and that structure solves a particular design problem in a specified content.

4. Modularity
  • A software is separately divided into name and addressable components. Sometime they are called as modules which integrate to satisfy the problem requirements.
  • Modularity is the single attribute of a software that permits a program to be managed easily.
5. Information hiding
Modules must be specified and designed so that the information like algorithm and data presented in a module is not accessible for other modules not requiring that information.

6. Functional independence
  • The functional independence is the concept of separation and related to the concept of modularity, abstraction and information hiding.
  • The functional independence is accessed using two criteria i.e Cohesion and coupling.
Cohesion
  • Cohesion is an extension of the information hiding concept.
  • A cohesive module performs a single task and it requires a small interaction with the other components in other parts of the program.
Coupling
Coupling is an indication of interconnection between modules in a structure of software.

7. Refinement
  • Refinement is a top-down design approach.
  • It is a process of elaboration.
  • A program is established for refining levels of procedural details.
  • A hierarchy is established by decomposing a statement of  function in a stepwise manner till the programming language statement are reached.
8. Refactoring
  • It is a reorganization technique which simplifies the design of components without changing its function behaviour.
  • Refactoring is the process of changing the software system in a way that it does not change the external behaviour of the code still improves its internal structure.
9. Design classes
  • The model of software is defined as a set of design classes.
  • Every class describes the elements of problem domain and that focus on features of the problem which are user visible.
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