undefined | unit 1 introduction software processes

UNIT 1

Introduction & Software Processes

Q1) What is Software Process Model? Elaborate?

A1)

A software process model is a specified definition of a software process, which is presented from a particular perspective. Models, by their nature, are a simplification, so a software process model is an abstraction of the actual process, which is being described. Process models may contain activities, which are part of the software process, software product, and the roles of people involved in software engineering. Some examples of the types of software process models that may be produced are:

A workflow model: This shows the series of activities in the process along with their inputs, outputs and dependencies. The activities in this model perform human actions.

2. A dataflow or activity model: This represents the process as a set of activities, each of which carries out some data transformations. It shows how the input to the process, such as a specification is converted to an output such as a design. The activities here may be at a lower level than activities in a workflow model. They may perform transformations carried out by people or by computers.

3. A role/action model: This means the roles of the people involved in the software process and the activities for which they are responsible.

There are several various general models or paradigms of software development:

The waterfall approach: This takes the above activities and produces them as separate process phases such as requirements specification, software design, implementation, testing, and so on. After each stage is defined, it is "signed off" and development goes onto the following stage.

Evolutionary development: This method interleaves the activities of specification, development, and validation. An initial system is rapidly developed from a very abstract specification.

Formal transformation: This method is based on producing a formal mathematical system specification and transforming this specification, using mathematical methods to a program. These transformations are 'correctness preserving.' This means that you can be sure that the developed programs meet its specification.

System assembly from reusable components: This method assumes the parts of the system already exist. The system development process target on integrating these parts rather than developing them from scratch.

Q2) Give advantages and disadvantages of Prototyping model?

A2)

ADVANTAGES

Provides a working model to the user early in the process, enabling early assessment and increasing user confidence.
Developer gains experience and insight by developing a prototype, thereby resulting in better implementation of requirements.
Prototyping model serves to clarify requirements,
which are not clear, hence reducing ambiguity and
Improving communication between developer and user.
There is a great involvement of users in software development. Hence, the requirements of the users are met to the greatest extent.
Helps in reducing risks associated with the project

DISADVANTAGES

If the user is not satisfied by the developed prototype, then a new prototype is developed.
This process goes on until a perfect prototype is developed. Thus, this model is time consuming and expensive.
Developer loses focus of the real purpose of prototype and compromise with the quality of the product. For example, they apply some of the inefficient algorithms or inappropriate programming languages used in developing the prototype.
Prototyping can lead to false expectations. It often creates a situation where user believes that the development of the system is finished when it is not.
The primary goal of prototyping is rapid development, thus, the design of system can suffer as it is built in a series of layers without considering integration of all the other

components

Q3) Explain software along with its characteristics?

A3)

Software is a collection of programs, documentation and operating procedures. The Institute of Electrical and Electronic Engineers (IEEE) defines software as a ‘collection of computer programs, procedures, rules and associated documentation and data.’ It possesses no mass, no volume, and no colour, which makes it a non-degradable entity over a long period.

Software Characteristics

Software characteristics are classified into six major components.

• Functionality: Refers to the degree of performance of the software against its intended purpose.

• Reliability: Refers to the ability of the software to provide desired functionality under the given conditions.

• Usability: Refers to the extent to which the software can be used with ease.

• Efficiency: Refers to the ability of the software to use system resources in the most effective and efficient manner.

Maintainability: Refers to the ease with which the modifications can be made in a software system to extend its functionality, improve its performance, or correct errors.

• Portability: Refers to the ease with which software developers can transfer software from one platform to another, without (or with minimum) changes. In simple terms, it refers to the ability of software to function properly on different hardware and software platforms without making any changes in it.

Robustness and integrity are also important. Robustness refers to the degree to which the software can keep on functioning in spite of being provided with invalid data while integrity refers to the degree to which unauthorized access to the software or data can be prevented

Q4) Explain more about the waterfall model?

A4)

This method is very old and fashionable which is often used because simplicity is the key to the success of this method. In this way all the steps taken are pre-programmed in the software development process. For small size projects the waterfall method is very convenient.

The uniqueness of this method is that each section has a sequence. After the end of one phase, the next phase begins at that point and the result of each phase is changed to include in all subsequent steps. So for this reason the second name of this model is Sequence Model. With systematic research the first phase began and after this analysis, design, coding, testing and control took place one by one. All the sections are completed one by one in a water-like sequence so this is the reason for the name.

Advantages of a waterfall

Due to the simplicity and sequencing. it is very easy to use.

The user can understand it quickly because it is simple.

It explains the full details of every step.

This model is very helpful in planning and organizing projects.

Reduce the cost of error with accuracy.

it increases the chances of the system meeting the needs of the customers.

Waterfall Limitations

Expectations become very fast in this wrong process.

Risk factors not involved in this model which is a much needed component in every model.

This way user training times are not required.

We cannot detect any errors until the software testing period is not performed.

Between user and developer the communication gap is low.

Q5) Why we need software Configuration Management?

A5)

Multiple people are working on software which is consistently updating. It may be a method where multiple version, branches, authors are involved in a software project, and the team is geographically distributed and works concurrently. It changes in user requirements, and policy, budget, schedules need to be accommodated.

Importance of SCM

It is practical in controlling and managing the access to various SCIs e.g., by preventing the two members of a team for checking out the same component for modification at the same time.

It provides the tool to ensure that changes are being properly implemented.

It has the capability of describing and storing the various constituent of software.

SCM is used in keeping a system in a consistent state by automatically producing derived version upon modification of the same component.

Q6) Elaborate Phases in software engineering?

A6)

Software engineering is an engineering disciplines where steps or phases occur in software development and primary aim of software engineering is to develop high quality software reasonable cost and less time, it is essential to perform software development in phases. This phased development is referred to as software development life cycle (SDLC) or software life cycle.

A software development process comprises of different phases. These phases work in top to bottom approach, implying that the phases take inputs from the previous phases, add features, and then produce outputs. The outputs from different phases are referred to as intermediate product, work product, or derivable. The various phases involved in the systematic development of software are shown in Figure below.

FIGURE 1: Software development process

Preliminary Investigation

Preliminary investigation verifies the problem and understands the need for required system. It considers whether the proposed system will be cost effective from business point of view and whether it can be developed within existing budgetary constraints. In addition, time factor, which determines the duration of the project, is also considered. Preliminary investigation should be quick and cost effective.

The output of preliminary investigation decides whether the new system should be developed or not.

There are three deciding constraints:

• Technical: it evaluates determines whether technology needed for proposed system is available or not and if it is available then how can it be integrated within the organization.it also determines whether the existing system can be upgraded to use new technology and whether the organization has the expertise to use it or not.

• Time: it determines the time needed to complete a project. Time is an important issue in software development as cost increases with an increase in the time period of a project.

• Budgetary: it examines the financial aspect of the project. Budgetary

Evaluation determines whether the investment needed to implement the system will be recovered at later stages or not.

(a) Software Analysis: analysis of requirements is done in detail. Analysing the requirements of the user is documented in software requirement specification (SRS) is developed, planning for the project begins after it.

(b) Software Design: In this phase the requirements are ‘defined’ as a plan and Designing begins with deciding information structures, in terms of efficiency, flexibility, and reusability. During this phase, strategic and tactical decisions are made to meet the required functional and quality requirements of a system. Software design serves as the blueprint for the implementation of requirement in the software system.

(c) Software Coding: This phase can be defined as a process of translating the software requirements into a programming language using tools that are available. Writing a software code requires a thorough knowledge of programming language and its tools. Therefore, it is important to choose the appropriate programming language according to the user requirements.

(c) Software Testing: This testing is performed to assure that software is free from errors. Efficient testing improves the quality of software. To achieve this, software testing requires a thorough analysis of the software in a systematic manner. Test plan is created to test software in a planned and systematic manner. In addition, software testing is performed to ensure that software produces the correct outputs. This implies that outputs produced should be according to user requirements.

(d) Software Maintenance: This phase comprises of a set of software engineering activities that occur after software is delivered to the user. The objective of software maintenance is to make software operational according to user requirements. The need of software maintenance is to provide continuity of service. This implies that software maintenance focuses on fixing errors, recovering from failures, such as hardware failures, or incompatibility of hardware with software. In addition, it facilitates future maintenance work by modifying the software code and databases used in the software.

Q7) Define Product and Process?

A7)

Product: What is delivered to the customer, is called a product. It may include source code, specification document, manuals, documentation etc. Basically, it is nothing but a set of deliverables only.

Process: Process is the way in which we produce software. It is the collection of activities that leads to (a part of) a product. An efficient process is required to produce good quality products.

Q8) Write a short note on Software Design Principles?

A8)

Software design should correspond to the analysis model: Often a design element corresponds to many requirements, therefore, we must know how the design model satisfies all the requirements represented by the analysis model.

Choose the right programming paradigm: A programming paradigm describes the structure of the software system. Depending on the nature and type of application, different programming paradigms such as procedure oriented, object-oriented, and prototyping paradigms can be used. The paradigm should be chosen keeping constraints in mind such as time, availability of resources and nature of user’s requirements.

Software design should be uniform and integrated: Software design is considered uniform and integrated, if the interfaces are properly defined among the design components. For this, rules, format, and styles are established before the design team starts designing the software.

Software design should be flexible: Software design should be flexible enough to adapt changes easily. It is done by basic design concepts such as abstraction, refinement, and modularity.

Software design should ensure minimal conceptual (semantic) errors: The design team must ensure that major conceptual errors of design such as ambiguousness and inconsistency are addressed in advance before dealing with the syntactical errors present in the design model.

Software design should be structured to degrade gently: Software should be designed to handle unusual changes and circumstances, and if the need arises for termination, it must do so in a proper manner so that functionality of the software is not affected.

Software design should represent correspondence between the software and real-world problem: The software design should be structured in such a way that it always relates with the real-world problem.

Software reuse: Software engineers believe on the phrase: ‘do not reinvent the wheel’. Therefore, software components should be designed in such a way that they can be effectively reused to increase the productivity.

Designing for testability:first the software is developed (designed and implemented) and then handed over to the testers who subsequently determine whether the software is fit for distribution and subsequent use by the customer. However, the process of separating testing is seriously flawed, as if any type of design or implementation errors are found after implementation, then the entire or a substantial part of the software requires to be redone. Thus, the test engineers should be involved from the initial stages

Prototyping: Prototyping should be used when the requirements are not completely defined in the beginning. The user interacts with the developer to expand and refine the requirements as the development proceeds. Using prototyping, a quick ‘mock-up’ of the system can be developed.

Q9) Write a short note on Spiral model?

A9)

IEEE defines spiral model as “a model of the software development process in which the constituent activities, typically requirements analysis, preliminary and detailed design, coding, integration, and testing, are performed iteratively until the software is complete.”

The objective of spiral model is to emphasise management to evaluate and resolve risks in the software project. This model combines the features of prototyping model and waterfall model and is advantageous for large, complex and expensive projects. The spiral model determines requirement problems in developing the prototypes. In addition, spiral model guides and measures the need of risk management in each cycle of the spiral model.

Advantages	Disadvantages
Avoids the problems resulting in risk-driven approach in the software.	Assessment of project risks and its resolution is not an easy task.
Specifies a mechanism for software quality assurance activities.	Difficult to estimate budget and schedule in the beginning, as some of the analysis is not done until the design of the software is developed.
Spiral model is utilised by complex and dynamic projects.
Re-evaluation after each step allows changes in user perspectives, technology advances or financial Perspectives.
Estimation of budget and schedule gets realistic as the work progresses.

Q10) Explain Process Management and Product Engineering Process?

A10)

The process management processes (PMP) aims at improving software processes so that a cost effective and a high quality product is developed. To achieve a high quality product, the existing processes of the completed project are examined. The process of comprehending the existing process, analysing its properties, determining how to improve it, and then affecting the improvement is carried out by PMP. A group known as software engineering process group (SEPG) performs the activities of process management.

Based on the analysis stated above, the product engineering processes are improved, thereby improving the software process. The aim of product engineering processes is to develop the product according to user requirements. The product engineering process comprises of three major components, which are listed below:

• Development process: Implies the process, which is used during the development of software. It specifies the development and quality assurance activities that are to be performed. Programmers, designers, testing personnel, and others perform these processes.

• Project management process: Provides means to plan, organise and control the allocated resources to accomplish project costs, time and performance objectives. For this, various processes, techniques and tools are used to achieve the objectives of the project. Project management performs the activities of this process. Also, project management process is concerned with the set of activities or tasks, which are used to successfully accomplish a set of goals.

• Configuration control process: Manages changes that occur as a result of modifying the requirements. In addition, it maintains integrity of the products with the changedrequirements. The activities in configuration control process are performed by a group called configuration control board (CCB).

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