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Software Process1. Software Process Model

2. Process Iteration

3. Software Specifications

4. Software design and implementation

5. Software validation

6. Software evolution

Satya Prakash Joshi (012BIM31)

Bipin Thapa (012BIM11)

Harish Chand (012BIM15)

Ganesh Pant (012BIM14)

2 Software Process Models

Software process model is organizing a structured set of activities to develop a software systems. [i.e. known as life cycle]

Specification

Design and implementation

Validation

Evolution

A software process model is an abstract representation of process. It presents a description of a process from particular perspective.

3 Generic Process Models

The waterfall model

Defines specification, development, validation and evolution and represent separate process phases requirement specifications, software design, implementation, testing etc…

Evolutionary development

Initial system is developed from abstract specifications. Refined with customer input to produce a system that satisfies the customers needs.

Component-based software engineering

The system is assembled from existing components rather then developing them developing from scratch.

4 Waterfall Model

First published model of the software development process.

System development method that is linear and sequential.

Once a phase of development is competed, the development proceeds to the next phase and never turns back.

5 Figure of Waterfall Model

6 Advantage and Disadvantage

The advantages of the waterfall model are that documentation is produced at each phase and that it fits with other engineering process models.

Easy to understand and use.

It’s major problem is it’s inflexible portioning of the project into distinct stages.

Difficult to change customers requirement at the middle of the software development process.

7 Conclusion of Waterfall

The waterfall model should only be used when the requirements are well understood and unlikely to change radically during system development.

8 Evolutionary Development

Evolutionary development is based on the idea of developing an initial implementation, exposing this to user comment and refining it through many version until an adequate system has been developed.

An Evolutionary approach to software development is often more effective than the waterfall approach in producing system that meet the immediate needs of customer.

The advantage of a software process that is based on an evolutionary approach is that the specification can be developed incrementally.

9 Figure of Evolutionary Development

10 Type of Evolutionary Development

Exploratory development :

Explores the customers requirement and develop the final system for customer.

Developer will know the parts of system and add new features proposed by the customer.

Throwaway prototyping

Process is to understand the customers requirement and develop.

Concentrates on experimenting with the customer requirement that are poorly understood.

11 Problems with Evolutionary Approach

The process is not visible

Managers need regular deliverables to measure progress. If systems are developed quickly, it is not cost-effective to produce documents that reflect every version of the system.

Systems are often poorly structured

Continual changes tends to corrupt the software structure. Incorporating software changes becomes increasingly difficult and costly.

12 Component-based software engineering

Majority of software projects, there is some software reuse.

When people working on the project known of the designs or code which is similar to that required. They look for these, modify them as needed and incorporated them into their system.

This information reuse takes place irrespective of the development process that is used. [increasingly used.]

Reuse oriented approach relies on a large base of reusable software components and some integrating framework for these components. [they claim their own rights i.e. COTS – Commercial off –the shelf systems]

13 Figure of CBSE

14 Advantage of CBSE

ROSE (Reuse-Oriented Software Engineering) has the obvious advantages of reduces software development complexity

Reduce cost and risks.

Easy to develop and modify.

Faster delivery of software.

Easy to maintenance and code reusability.

15 Process Iteration

Iterative development is a way of breaking down the software development of a large application into smaller chunks.

In iterative development,  feature code is designed, developed and tested in repeated cycles.

With each iteration, additional features can be designed, developed and tested until there is a fully functional software application ready to be deployed to customers.

Iterative and incremental development are key practices in Agile development methodologies.

16 Incremental Delivery

The software specifications, design and implementation are broken down into a series of increments that are each developed in turn.

Incremental delivery process will combine the advantages of waterfall, evolutionary and CBSE.

In an incremental development process, customer identify the services to be provided by the system.

They identify which of the services are most important and which are least important to them.

17 Figure of Incremental Delivery

18 Advantages of Incremental Delivery

Customers do not have to wait until the entire system is delivered before they can gain value from it. The first incremental satisfies their most critical requirements so they can use the software immediately.

Customers can use the early increments as prototypes and gain experiences that information for later system increments.

There is a lower risk of overall project failure. Although problems may be encountered in some increments.

As the highest priority services are delivered first.

19 Spiral Development

Represent the software process as a sequence of activities with some backtracking one activity to another, the process is represented as a spiral.

This model is risk oriented and comprises the features of the prototype and waterfall model.

This model is used for larger projects, expensive and complicated projects because of where proper risk assessment is essential.

Users can see the system earl because of rapid prototyping features. Risk evaluation may take longer time in the system development process.

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21 Process Activities

Specifications

Development

Validation

Evolution

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System Requirement Specification (SRS)

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Definitions:

A software requirements specification (SRS) is a description of a software system to be developed, laying out functional and non-functional requirements, and may include a set of use cases that describe interactions the users will have with the software.

Software specifications, or specs, are documents which define the functionality and technical details of a software application or system.

A software requirements specification (SRS) is a comprehensive description of the intended purpose and environment for software under development.

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The SRS fully describes what the software will do and how it will be expected to perform.

A good SRS defines how an application will interact with system hardware, other programs and human users in a wide variety of real-world situations.

The basic purpose of SRS is to bridge the communication gap between the parties involved in the development of the software.

It provides feedback to the customer.

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Characteristics of SRS

Correct

Unambiguous

Complete

Consistent

Ranked Importance

Verifiable

Modifiable

Traceable

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Advantages of SRS

It establishes the basis of agreement between the client and the supplier on what the software product will do.

An SRS minimizes the time and effort required by developers to achieve desired goals and also minimizes the development cost.

It provides a reference for validation of the final product.

27System Design

the process of defining the architecture, components, modules, interfaces, and data for a system to satisfy specified requirements

seen as the application of systems theory to product development

design implies a systematic approach to the design of a system

the process is systematic wherein it takes into account all related variables of the system that needs to be created—from the architecture, to the required hardware and software, right down to the data and how it travels and transforms throughout its travel through the system

28Things to be aware of

What is the system?

What is the environment?

What goal does the system have in relation to its environment?

What is the feedback loop by which the system corrects its actions?

How does the system measure whether it has achieved its goal?

Who defines the system, environment, goal, etc.—and monitors it?

What resources does the system have for maintaining the relationship it desires?

Are its resources sufficient to meet its purpose?

29 System design steps

Define project goal and objectives Develop the project system requirements Identify the major system components that satisfy

the system requirements Identify the major system interfaces Refine the system design

Define subsystems making up each component Specify interfaces between subsystems

Establish management controls for the system interfaces

30 Types of design

1) Architectural design:- The architectural design of a system emphasizes on the design of the systems architecture which describes the structure, behavior, and more views of that system and analysis.

2) Logical design:- The logical design of a system pertains to an abstract representation of the data flows, inputs and outputs of the system. In the context of systems design are included. Logical design includes ER Diagrams i.e. Entity Relationship Diagrams.

313) Physical design:- The physical design relates to the actual input and output processes of the system. This is laid down in terms of how data is input into a system, how it is verified/authenticated, how it is processed, and how it is displayed as In Physical design, the following requirements about the system are decided.

Input requirement,

Output requirements,

Storage requirements,

Processing Requirements,

System control and backup or recovery.

32System Implementation

This is one of the most vital phase as in this phase the analyst actually gives the system to the customer and expects for a positive feedback.

Is the process of converting the design in a real system through coding.

Implementation phase includes coding and testing.

This Phase will provide users with the documentation and training required to use the system effectively.

Data Conversion will only occur once, but user documentation will be required.

33Coding Phase

In the coding/development phase the individual objects or components of the application are coded from the physical model.

Once the system objects have been developed, they are gathered and connected together (integrated) to create a working application.

The integrated application is placed on a staging server for testing.

Developers have to follow the coding guidelines defined by their organization and programming tools like compilers, interpreters, debuggers etc are used to generate the code

For E.g. C, C++, Pascal, Java, and PHP are used for coding. 

34Testing Phase

Once the engineer is through with the coding stage he tests the systems and sees to it that it is working as per the expectations or not.

He corrects the flaws in the system if any.

Testing is becoming more and more important to ensure customer’s satisfaction, and it requires no knowledge in coding, hardware configuration or design.

35Testing Types

1) Static Testing :- Static testing refers to testing something that’s not running.

It is examining and reviewing it. i.e., to check whether the work done meets the standards of the organization.

Reviews, Inspections and Walk-throughs are static testing methodologies.

Example: The specification is a document and not an executing program. When we read it to find out the issues, it is considered as static testing.

362) Dynamic Testing:-

Dynamic Testing involves working with the software, giving input values and checking if the output is as expected.

These are the Validation activities. Unit Tests, Integration Tests, System Tests and Acceptance

Tests are few of the Dynamic Testing methodologies.

Techniques used are determined by type of testing that must be conducted.

Functional ("black box") testing :- Black box testing involves looking at the specifications and does not require examining the code of a program. Tests that examine the observable behavior of software as evidenced by its outputs without referencing to internal functions is black box testing.

Structural (usually called "white box") testing:- white box testing requires programming knowledge to know the internals of the code. Also it is time consuming. So only a developer can become a white box tester.

37System Documentation

Software documentation is an important part of software process.

A well written document provides a great tool and means of information repository necessary to know about software process.

Software documentation also provides information about how to use the product.

38Requirement documentation

This documentation works as key tool for software designer, developer and the test team to carry out their respective tasks.

This document contains all the functional, non-functional and behavioral description of the intended software.

39Software Design documentation

These documentations contain all the necessary information, which are needed to build the software.

It contains:

(a) High-level software architecture

(b) Software design details

(c) Data flow diagrams

(d) Database design

40Technical documentation

These documentations are maintained by the developers and actual coders.

These documents, as a whole, represent information about the code.

While writing the code, the programmers also mention objective of the code, who wrote it, where will it be required, what it does and how it does, what other resources the code uses, etc.

41User documentation

This documentation is different from all the above explained.

All previous documentations are maintained to provide information about the software and its development process.

But user documentation explains how the software product should work and how it should be used to get the desired results.

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Software Validation

43 Software Validation is the process of checking that a software system meets specifications and that it fulfills its intended purpose.

It may also be referred to as software quality control.

Validation checks that the product design satisfies or fits the intended use (high-level checking), i.e., the software meets the user requirements. This is done through dynamic testing and other forms of review.

It verifies that the software being developed implements all the requirements specified in the SRS document.

Software validation is the process of ensuring that your application meets functional and non-functional requirements before coding and during development.

44Software Evolution Generally, software evolution refers to the study and management of the

process of making changes to software over time. software evolution comprises:

• Development activities:

Sometimes, software evolution is used to refer to the activity of adding new functionality to existing software.

• Maintenance activities:

Maintenance refers to the activity of modifying software after it has been put to use in order to maintain its usefulness.

• Reengineering activities:

Rewriting all or parts of the system to Improve the program structure system performance

45 Importance of Evolution

Organizations have huge investments in their software systems - they are critical business assets.

To maintain the value of these assets to the business, they must be changed and updated.

The majority of the software budget in large companies is devoted to evolving existing software rather than developing new software.

Saves money and Time

Accuracy can be maintained

Flexibility

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