The Software Process • What? A software process – as a framework for the

tasks that are required to build high-quality software.

• Who does? Managers, software engineers, and customers.

• Why? Provides stability, control, and organization otherwise chaotic(disorder) activity.

• Steps? General activities are common to all software processes, details vary.

• Work product? Programs, documents, and data.

What is software Engg.?• Definition :

– (1) The application of systematic, disciplined, quantifiable approach to the development, operation, and maintenance of software; that is, the application of engineering to software.

– (2) The study of approaches as in (1) above• Its a discipline that is concerned with all aspects of software production.

• Software engineers should adopt – Systematic and organized approach to their work – Use appropriate tools and techniques depending on the problem

to be solved– The development constraints and the resources available

• Apply Engineering Concepts to developing Software

• Challenge for Software Engineers is to produce high quality software with finite amount of resources & within a predicted schedule

Software Engineering – Layered Technology

Layered Technology

A quality focus: the A quality focus: the ““bedrockbedrock””

Process model: the Process model: the ““frameworkframework””

Methods: technical Methods: technical ““how tohow to’’ss””

Tools: CASE preferredTools: CASE preferred

Layered TechnologyA quality Focus• Every organization is rest on its commitment to quality.• Total quality management, Six Sigma, or similar continuous

improvement culture and it is this culture ultimately leads to development of increasingly more effective approaches to software engineering.

• The bedrock(foundation) that supports software engineering is a quality focus.

Process:• It’s a foundation layer for software engineering.• It’s define framework for a set of key process areas (KPA) for effectively

manage and deliver quality software in a cost effective manner • The processes define the tasks to be performed and the order in which

they are to be performed • Provides the glue that holds the layers together;

Layered Technology

Methods:• It provide the technical how-to's for building software.• Methods encompass a broad array of tasks that include requirements analysis,

design, program construction, testing, and support.• There could be more than one technique to perform a task and different

techniques could be used in different situations.

Tools:• Provide automated or semi-automated support for the process, methods and

quality control. • When tools are integrated so that information created by one tool can be used

by another, a system for the support of software development, called computer-aided software engineering (CASE)

Generic Process Framework

• A process framework establishes the foundation for a complete software process by identifying a small number of framework activities.

• Frame work activities are applicable to all software projects.

Generic Process Model

A generic process framework for software engineering defines five framework activities-communication, planning, modeling, construction, and deployment.

In addition, a set of umbrella activities- project tracking and control, risk management, quality assurance, configuration management, technical reviews, and others are applied throughout the process.

Next question is: how the framework activities and the actions and tasks that occur within each activity are organized with respect to sequence and time?

Process frameworkWhy process :

A process defines who is doing what, when and how to reach a certain goal to build complete software process.

• Identified a small number of framework activities that are applicable to all software projects, regardless of their size or complexity.

• It encompasses a set of umbrella activities that are applicable across the entire software process.

Process Framework•Each framework activities is populated by a set for software engineering actions – a collection of related tasks.• Each action has individual work task.

Generic Process Framework Activities

• Communication: – Heavy communication with customers, stakeholders, team– Encompasses requirements gathering and related activities

• Planning: – Workflow that is to follow– Describe technical task, likely risk, resources will require,

work products to be produced and a work schedule.• Modeling:

– Help developer and customer to understand requirements (Analysis of requirements) & Design of software

• Construction:– Code generation: either manual or automated or both– Testing – to uncover error in the code.

• Deployment:– Delivery to the customer for evaluation– Customer provide feedback

Umbrella Activities• Software project Management or tracking and control

– Assessing progress against the project plan.– Take adequate action(Sufficient) to maintain schedule.

• Formal technical reviews– Assessing software work products in an effort to uncover and remove

errors before goes into next action or activity. • Software quality assurance

– Define and conducts the activities required to ensure software quality. • Software configuration management

– Manages the effects of change. • Document preparation and production

– Help to create work products such as models, documents, logs, form and list. • Reusability management

– Define criteria for work product reuse– Mechanisms to achieve reusable components.

• Measurement– Define and collects process, project, and product measures– Assist the team in delivering software that meets customer’s needs.

• Risk management– Assesses risks that may effect that outcome of project or quality of product (i.e.

software)

Capability Maturity Model Integration (CMMI)

• The Software Engineering Institute (SEI) has developed process meta-model to measure organization different level of process capability and maturity.

• CMMI – developed by SEI• The CMMI defines each process area in terms of “specific

goals” and the “specific practices” required to achieve these goals.

• Specific goals establish the characteristics that must exist if the activities implied by a process area are to be effective.

• Specific practices refine a goal into a set of process-related activities.

CMMI LevelLevel 1: Initial. The software process is characterized as

ad hoc and occasionally even chaotic.

Few processes are defined, and success depends on individual effort.

Level 2: Repeatable. Basic project management processes are established to track cost, schedule, and functionality.

The necessary process discipline is in place to repeat earlier successes on projects with similar applications.

CMMI Level (cont.)Level 3: Defined. The software process for both management and engineering activities is documented,

standardized, and integrated into an organization wide software process. All projects use a documented and approved version of the organization's process

for developing and supporting software. This level includes all characteristics defined for level 2.

Level 4 (Quantitatively Managed) -– All level 3 criteria have been satisfied.– Software process and products are quantitatively understood– Controlled using detailed measures and assessment.

Level 5 (Optimized) – This level includes all characteristics defined for level 4. – Continuous process improvement is enabled by quantitative feedback from the

process and testing innovative ideas & technology

HemalKumar Rajyaguru

• The process model can be defined as the abstract representation of process.

• Process models prescribe a distinct set of activities, actions, tasks, milestones, and work products required to engineer high quality software.

• Process models are not perfect, but provide roadmap for software engineering work.

• Software models provide stability, control, and organization to a process that if not managed can easily get out of control

• Software process models are adapted to meet the needs of software engineers and managers for a specific project.

Software process model / SDLC

HemalKumar Rajyaguru

Waterfall Model or Classic Life Cycle(CPMCD)

• Requirement Analysis and Definition: The systems services, constraints and goals are defined by customers with system users.

• Scheduling tracking - – Assessing progress against the project plan.– Require action to maintain schedule.

• System and Software Design: How –It establishes and overall system architecture. Software design involves fundamental system abstractions and their relationships.

• Integration and system testing: The individual program unit or programs are integrated and tested as a complete system to ensure that the software requirements have been met. After testing, the software system is delivered to the customer.

• Operation and Maintenance: Normally this is the longest phase of the software life cycle. The system is installed and put into practical use. Maintenance involves correcting errors which were not discovered in earlier stages of the life-cycle.

Waterfall Model or Classic Life Cycle

Limitations of the waterfall model The nature of the requirements will not change very much During development;

during evolution

The model implies that you should attempt to complete a given stage before moving on to the next stage

Does not account for the fact that requirements constantly change. It also means that customers can not use anything until the entire system

is complete. The model implies that once the product is finished, everything else is

maintenance.

Surprises at the end are very expensive

Some teams sit ideal for other teams to finish

Therefore, this model is only appropriate when the requirements are well-understood and changes will be fairly limited during the design process.

• Problems:1. Real projects are rarely follow the sequential

model.

2. Difficult for the customer to state all the requirement in advance.

3. Assumes patience from customer - working version of program will not available until programs not getting change fully.

Problem

When to use waterfall model• Requirements are very well known, clear and

fixed• Product definition is stable• Technology is understood• There are no ambiguous requirements• Ample resources with required expertise are

available freely• The project is short

Pros Cons•Simple and easy to understand and use•Easy to manage due to the rigidity of the model . •Each phase has specific deliverables and a review process.•Phases are processed and completed one at a time.•Works well for smaller projects where requirements are very well understood.•Clearly defined stages.•Well understood milestones.•Easy to arrange tasks.•Process and results are well documented.

•No working software is produced until late during the life cycle.•High amounts of risk and uncertainty.•Not a good model for complex and object-oriented projects.•Poor model for long and ongoing projects.•Not suitable for the projects where requirements are at a moderate to high risk of changing. So risk and uncertainty is high with this process model.•It is difficult to measure progress within stages.•Cannot accommodate changing requirements.•No working software is produced until late in the life cycle.•Adjusting scope during the life cycle can end a project.•Integration is done as a "big-bang. at the very end, which doesn't allow identifying any technological or business bottleneck or challenges early.

Waterfall Model with Feedback(Diagram)

CommunicationProject initiation

Requirements gathering

PlanningEstimatingSchedulingTracking Modeling

AnalysisDesign Construction

CodeTest Deployment

DeliverySupport

Feedback

Incremental Process Model

C- CommunicationP - PlanningM – ModelingC - ConstructionD - Deployment

Delivers software in small but usable pieces, each piece builds on pieces already delivered

• Rather than deliver the system as a single delivery, the development and delivery is broken down into increments with each increment delivering part of the required functionality.

• First Increment is often core product– Includes basic requirement– Many supplementary features (known & unknown) remain

undelivered• A plan of next increment is prepared

– Modifications of the first increment– Additional features of the first increment

• It is particularly useful when enough staffing is not available for the whole project

• Increment can be planned to manage technical risks.• Incremental model focus more on delivery of operation product

with each increment.

The Incremental Model

• User requirements are prioritised and the highest priority requirements are included in early increments.

• Once the development of an increment is started, the requirements are frozen though requirements for later increments can continue to evolve.

• Customer value can be delivered with each increment so system functionality is available earlier.

• Early increments act as a prototype to help obtain requirements for later increments.

• Lower risk of overall project failure.• The highest priority system services tend to receive the most

testing.

The Incremental Model

• Generates working software quickly and early during the software life cycle.

• This model is more flexible – less costly to change scope and requirements.

• It is easier to test and debug during a smaller iteration.

• In this model customer can respond to each built.• Lowers initial delivery cost.• Easier to manage risk because risky pieces are

identified and handled during iteration

Advantages Incremental Model

• Needs good planning and design.• Needs a clear and complete definition of the whole

system before it can be broken down and built incrementally.

• Total cost is higher than waterfall.

Disadvantages Incremental Model

• This model can be used when the requirements of the complete system are clearly defined and understood.

• Major requirements must be defined; however, some details can evolve with time.

• There is a need to get a product to the market early.• A new technology is being used• Resources with needed skill set are not available• There are some high risk features and goals.

When to use Incremental Model ?

Rapid Application Development (RAD) Model

Makes heavy use of reusable software components with an extremely short development cycle

RAD model• Communication – to understand business problem.• Planning – multiple s/w teams works in parallel on diff. system.• Modeling –

– Business modeling – Information flow among business is working.Ex. What kind of information drives? Who is going to generate information? From where information comes and goes? – Data modeling – Information refine into set of data objects that are

needed to support business.– Process modeling – Data object transforms to information flow

necessary to implement business.

RAD model• Construction – it highlighting the use of pre-existing software

component.

• Deployment – Deliver to customer basis for subsequent iteration.

• RAD model emphasize a short development cycle.• “High speed” edition of linear sequential model.• If requirement are well understood and project scope is

constrained then it enable development team to create “ fully functional system” within a very short time period.

RAD ModelDrawback:• For large but scalable projects

– RAD requires sufficient human resources• Projects fail if developers and customers are not

committed in a much shortened time-frame• Problematic if system can not be modularized• Not appropriate when technical risks are high

( heavy use of new technology)

Evolutionary Process Model

• Produce an increasingly more complete version of the software with each iteration.

• Evolutionary Models are iterative. • Evolutionary models are:

– Prototyping– Spiral Model– Concurrent Development Model

Evolutionary Process Models : Prototyping

Prototyping Model • Best approach when:

– Objectives defines by customer are general.– Developer may be unsure of the efficiency of an algorithm,

O.S., etc.• It assist engineer and customer to better understand what is to

be built when requirement are fuzzy.• Planned quickly and modeling (software layout visible to the

customers/end-user) occurs.• Feedback from customer/end user will refine requirement.

Prototyping (cont..)

Prototype can be serve as “the first system”.

Both customers and developers like the prototyping paradigm. Customer/End user gets a feel for the actual

system Developer get to build something immediately.

Prototyping (cont..)Problem Areas:Customer demand that “a few fixes” be applied

to make the prototype a working product, due to that software quality suffers as a result.

Developer often makes implementation in order to get a prototype working quickly without considering other factors in mind like OS, Programming language, etc.

Advantages Prototype Model• Users are actively involved in the development• Since in this methodology a working model of the system is

provided, the users get a better understanding of the system being developed.

• Errors can be detected much earlier.• Quicker user feedback is available leading to better solutions.• Missing functionality can be identified easily• Confusing or difficult functions can be identified

Requirements validation, Quick implementation of, incomplete, butfunctional, application.

Disadvantages Prototype Model• Leads to implementing and then repairing way of building systems.• Practically, this methodology may increase the complexity of the

system as scope of the system may expand beyond original plans.• Incomplete application may cause application not to be used as

thefull system was designedIncomplete or inadequate problem analysis.

When to Use Prototype Model?• Prototype model should be used when the desired system needs

to have a lot of interaction with the end users.• Typically, online systems, web interfaces have a very high amount

of interaction with end users, are best suited for Prototype model. • Prototyping ensures that the end users constantly work with the

system and provide a feedback which is incorporated in the prototype to result in a useable system.

Evolutionary Model: Spiral Model

Spiral Model Couples iterative nature of prototyping with the

controlled and systematic aspects.• Using spiral, software developed in as series of

evolutionary release.– Early iteration, release might be on paper

or prototype.– Later iteration, more complete version of

software.• Divided into framework activities (C,P,M,C,D). Each

activity represent one segment. • Unlike other process models that end when software

is delivered.

Spiral Model

Spiral Model

Advantages of Spiral Model• High amount of risk analysis hence, avoidance of Risk is enhanced.• Good for large and mission-critical projects.• Strong approval and documentation control.• Additional Functionality can be added at a later date.• Software is produced early in the software life cycle.

Disadvantages of Spiral Model• Can be a costly model to use.• Risk analysis requires highly specific expertise.• Project’s success is highly dependent on the risk analysis phase.• Doesn’t work well for smaller projects.

When to use Spiral Model• When costs and risk evaluation is important• For medium to high-risk projects• Long-term project commitment unwise because of potential

changes to economic priorities• Users are unsure of their needs• Requirements are complex• New product line• Significant changes are expected (research and exploration)

Selection of a Life Cycle Model

Selection of a model is based on:a) Requirements

b) Development team

c) Users

d) Project type and associated risk

50

Based On Characteristics Of RequirementsRequirements Waterfall Prototype Iterative

enhancementEvolutionary development

Spiral RAD

Are requirements easily understandable and defined?

Do we change requirements quite often?

Can we define requirements early in the cycle?

Requirements are indicating a complex system to be built

Yes Yes

Yes Yes

Yes Yes Yes Yes

Yes Yes Yes Yes

No

No

No

No

No

No No

No

No

No

No

No

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Development Team

Waterfall Prototype Iterative enhancement

Evolutionary development

Spiral RAD

Based On Status Of Development Team

Less experience on similar projects?

Less domain knowledge (new to the technology)

Less experience on tools to be used

Availability of training if required

Yes

Yes

Yes

Yes

Yes

Yes Yes

Yes

Yes

Yes

Yes

No

No

No

NoNo

No No No

No

No

No

NoNo

52

Based On User’s Participation

53

Concurrent Model• Allow a software team to represent iterative and concurrent

elements of any of the process models. • The Figure shows modeling may be in any one of the states at any

given time. • For example, communication activity has completed its first iteration

and in the awaiting changes state. The modeling activity was in inactive state, now makes a transition into the under development state.

• Concurrent modeling is applicable to all types of software development and provides an accurate picture of the current state of a project.

• Each activity, action or task on the network exists simultaneously with other activities, actions or tasks.

Concurrent Model

Agile Process Model• Agile SDLC model is a combination of iterative and

incremental process models with focus on process adaptability and customer satisfaction by rapid delivery of working software product.

Agile Process Model• Agile Methods break the product into small

incremental builds.• Every iteration involves cross functional teams

working simultaneously on various areas like planning, requirements analysis, design, coding, unit testing, and acceptance testing.

Advantages Agile Process Model• Customer satisfaction by rapid, continuous delivery of

useful software.• Customers, developers and testers constantly interact

with each other.• Close, daily cooperation between business people and

developers.• Continuous attention to technical excellence and good

design.• Regular adaptation to changing circumstances.• Even late changes in requirements are welcomed

Disadvantages Agile Process Model• In case of some software, it is difficult to assess the effort

required at the beginning of the software development life cycle.

• There is lack of emphasis on necessary designing and documentation.

• The project can easily get taken off track if the customer representative is not clear what final outcome that they want.

• Only senior programmers are capable of taking the kind of decisions required during the development process.

Component-based Development Model• Consists of the following process steps

– Available component-based products are researched and evaluated for the application domain in question

– Component integration issues are considered– A software architecture is designed to accommodate the

components– Comprehensive testing is conducted to ensure proper

functionality• Relies on a robust component library• Capitalizes on software reuse, which leads to documented

savings in project cost and time