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CIAT I Answer KeyCS6403 Software Engineering

Common to B.E CSE/ B.Tech IT (II/IV Semester) PART A 1. Define software engineering.

Software engineering: The application of a systematic, disciplined, quantifiable approach to the development, operation, and maintenance of software: that is, the application of engineering to software

2. What are the various categories of software?

* System software

* Application software

* Engineering/Scientific software

* Embedded software

3. What are the prescriptive and specialized process models?

Prescriptive process models:

The water fall model, Incremental process model, Evolutionary process model, and The spiral model

Specialized process models:

Component-based development, The formal methods model and Aspect-oriented software development

4. What are the merits of incremental model?

i) The incremental model can be adopted when there is less number of people involved in the project.

ii) Technical risks can be managed with each increment.

iii) For a very small time span, at least core product can be delivered to the customer.

5. What is COCOMO model?

COnstructive COst MOdel is a cost model, which gives the estimate of number of man-months it will take to develop the software product.

6. What is the difference between the Known Risks and Predictable Risks ?

Known Risks :-

That can be uncovered after careful evaluation of the project plan, the business, and technical environment in which the product is being developed

Example : Unrealistic delivery rate

Predictable Risks :-

Extrapolated from past project experience

Example : Staff turnover

7. What is EVA?

Earned Value Analysis is a technique of performing quantitative analysis of the software project.

It provides a common value scale for every task of software project. It acts as a measure for software project progress.

8. What is RMMM?

RMMM - Risk Mitigation Monitoring and Management. Its an effective strategy to assist the project team for dealing with risk

9. How is the risk exposure RE computed?

RE = p x c Where p = probability of occurrence for a risk

c = cost of the project10. What are the umbrella activities of a software process?

* Software project tracking and control.

* Risk management.

* Software Quality Assurance.

* Formal Technical Reviews.

* Software Configuration Management.

* Work product preparation and production.

* Reusability management.

* Measurement.

PART B (3 x 16 = 48 marks)1. a Explain about the evolutionary process model (16) Evolutionary models are iterative. They are characterized in a manner that enables you to develop increasingly more complete versions of the software Prototyping Follows an evolutionary and iterative approach Used when requirements are not well understood Serves as a mechanism for identifying software requirements Focuses on those aspects of the software that are visible to the customer/user Feedback is used to refine the prototypeProblems The customer sees a "working version" of the software, wants to stop all development and then buy the prototype after a "few fixes" are made Developers often make implementation compromises to get the software running quickly (e.g., language choice, user interface, operating system choice, inefficient algorithms) Define the rules up front on the final disposition of the prototype before it is built In most circumstances, plan to discard the prototype and engineer the actual production software with a goal toward quality Spiral Model

Invented by Dr. Barry Boehm in 1988 while working at TRW

Follows an evolutionary approach

Used when requirements are not well understood and risks are high

Inner spirals focus on identifying software requirements and project risks; may also incorporate prototyping

Outer spirals take on a classical waterfall approach after requirements have been defined, but permit iterative growth of the software

Operates as a risk-driven modela go/no-go decision occurs after each complete spiral in order to react to risk determinations

Requires considerable expertise in risk assessment Serves as a realistic model for large-scale software development

(or) b. Explain the iterative waterfall and the incremental model for software life cycle

and various activities in each phase (16) Oldest software lifecycle model and best understood by upper management Used when requirements are well understood and risk is low Work flow is in a linear (i.e., sequential) fashion Used often with well-defined adaptations or enhancements to current softwareProblems Doesn't support iteration, so changes can cause confusion Difficult for customers to state all requirements explicitly and up front Requires customer patience because a working version of the program doesn't occur until the final phase Problems can be somewhat alleviated in the model through the addition of feedback loops

Used when requirements are well understood Multiple independent deliveries are identified Work flow is in a linear (i.e., sequential) fashion within an increment and is staggered between increments Iterative in nature; focuses on an operational product with each increment Provides a needed set of functionality sooner while delivering optional components later Useful also when staffing is too short for a full-scale development2. a Explain project scheduling and scheduling process. Basic Principles Of Software Project Scheduling :-

Compartmentalization

Interdependency

Time Allocation

Effort Validation

Defined Responsibilities

Defined Outcomes

Scheduling of a software project does not differ greatly from scheduling of any multitask engineering effort.

Program evaluation and review technique (PERT)

critical path method (CPM)

Tasks, sometimes called the project work breakdown structure (WBS), are defined for the product as a whole or for individual functions.

quantitative tools

(1) determine the critical paththe chain of tasks that determines the duration of the project

(2) establish most likely time estimates for individual tasks by applying statistical models

(3) calculate boundary times that define a time window for a particular task.

Time-line chart

Tracking can be accomplished in a number of different ways:

Conducting periodic project status meetings in which each team member reports progress and problems

Evaluating the results of all reviews conducted throughout the software engineering process

Determining whether formal project milestones have been accomplished by the scheduled date

Comparing the actual start date to the planned start date for each project task listed in the resource table

Meeting informally with practitioners to obtain their subjective assessment of progress to date and problems on the horizon

Using earned value analysis to assess progress quantitatively

The time-boxing strategy recognizes that the complete product may not be deliverable by the predefined deadline. The tasks associated with each increment are then time-boxed.

WebApp project scheduling distributes estimated effort across the planned time line (duration) for building each WebApp increment.

seven increments. Each framework action can be adapted in one of four ways

(1) a task is applied as is,

(2) a task is eliminated because it is not necessary for the increment,

(3) a new (custom) task is added, and

(4) a task is refined (elaborated) into a number of named subtasks that each becomes part of the schedule.

(or) b Brief about calculating Earned Value Measures.(16)

a technique for performing quantitative analysis of progress does exist

To determine the earned value

The budgeted cost of work scheduled (BCWS) is determined for each work task represented in the schedule.

The BCWS values for all work tasks are summed to derive the budget at completion (BAC)

BAC = (BCWSk) for all tasks k Next, the value for budgeted cost of work performed (BCWP) is computed.

Schedule performance index, SPI = BCWP / BCWS

Schedule variance, SV = BCWP - BCWS

An SPI value close to 1.0 indicates efficient execution of the project schedule.

SV is simply an absolute indication of variance from the planned schedule.

Percent scheduled for completion = BCWS/BAC

Percent complete = BCWP/BAC

actual cost of work performed (ACWP)

the sum of the effort actually expended on work tasks that have been completed by a point in time on the project schedule

Cost performance index, CPI = BCWP / ACWP

Cost variance, CV = BCWP ACWP

A CPI value close to 1.0 provides a strong indication that the project is within its defined budget.

CV is an absolute indication of cost savings (against planned costs) or shortfall at a particular stage of a project.

Like over-the-horizon radar, earned value analysis illuminates scheduling difficulties before they might otherwise be apparent. This enables you to take corrective action before a project crisis develops.

3. a. Describe LOC and function point estimation with neat example (16)

(or)b. What are the categories of software risks? Give an overview about risk management.(16)two characteristics

Uncertainty

the risk may or may not happen; that is, there are no 100 percent probable risks

Loss

if the risk becomes a reality, unwanted consequences or losses will occur

When risks are analyzed, it is important to quantify the level of uncertainty and the degree of loss associated with each risk.

Project risks threaten the project plan.

the project schedule will slip and that costs will increase

identify potential budgetary, schedule, personnel, resource, stakeholder, and requirements problems and their impact on a software project

Technical risks threaten the quality and timeliness of the software to be produced.

implementation may become difficult or impossible

identify potential design, implementation, interface, verification, and maintenance problems

specification ambiguity, technical uncertainty, technical obsolescence, and leading-edge technology

because the problem is harder to solve than you thought it would be

Business risks threaten the viability of the software to be built and often jeopardize the project or the product

top five business risks are

(1) building an excellent product or system that no one really wants (market risk),

(2) building a product that no longer fits into the overall business strategy for the company (strategic risk),

(3) building a product that the sales force doesnt understand how to sell (sales risk),

(4) losing the support of senior management due to a change in focus or a change in people (management risk), and

(5) losing budgetary or personnel commitment (budget risks).

Known risks can be uncovered after careful evaluation of the project plan,

the business and technical environment in which the project is being developed,

other reliable information sources

Predictable risks are extrapolated from past project experience

Unpredictable risks are the joker in the deck.

They can and do occur, but they are extremely difficult to identify in advance

Risk Projection/Estimation Steps

1) Establish a scale that reflects the perceived likelihood of a risk (e.g., 1-low, 10-high)

2) Delineate the consequences of the risk

3) Estimate the impact of the risk on the project and product

4) Note the overall accuracy of the risk projection so that there will be no misunderstandingsAssessing Risk Factor

Three factors affect the consequences that are likely if a risk does occur

Its nature This indicates the problems that are likely if the risk occurs

Its scope This combines the severity of the risk (how serious was it) with its overall distribution (how much was affected)

Its timing This considers when and for how long the impact will be felt

The overall risk exposure formula is RE = P x C

P = the probability of occurrence for a risk

C = the cost to the project should the risk actually occur