Software Engineering

Developing a solution strategy
A solution strategy concerning the nature of possible
solutions.
The selected strategy provides a framework for
design and implementation of the software product.
Various strategies are there from that the best is done
by a group of people who have been trained in the
techniques of brain storming.
A solution strategy is feasible if the project goal and
requirements can be satisfied within the constraints of
available time ,resources and technology using that
strategy.

planning the development process:
software life cycle activities
 define
 develop
 test
 deliver
 operate
 maintain.

lifecycle activities are given above. These activities
are change
 no single life cycle models is used.
 Different models are used for various software
product.
 A life cycle model that is understood and accepted
by all concerned parties improves project
communications and project manageability , resource
allocations, cost control and product quality

The phased lifecycle model:
 Series of successive activities.
 Requires well defined input, process and results in
well defined output.
 Resources is required to complete each phase.
 Application of explicit methods, tools and techniques

Analysis consist of two sub phases
 Planning
 Requirements definition.
This phase includes
Understanding the customer problem.
 Performing a feasibility study.
 Developing solution stragedy
 Acceptance criteria
 Planning the development process.

The products of planning are
 System definitions.
 Project plan.
System definitions:
 Expressed in English or some other language.
 It includes charts, figures, graphs, tables, and
equations.

Project plan:
 Contains lifecycle model to be used.
 Organitational structure.
 Basic development schedule, resource estimate,
staffing requirements, tools and techniques to be used.
 Time and cost are basically calculated because it is
not possible to estimate exactly without doing basic
design.

Requirements definitions:
 It includes basic functions of software components
in hardware, software, and people subsystem.
The product of requirements definition:
 The product of requirements definition is a
specification that describes
 The processing environment
 The required software functions.
 Performance constraints on the software.
 Exception handling
 Acceptance criteria.

Design phase:
 In the phased model, software design follows analysis
 Design phase identified software components
I. Functions.
II. Data streams
III. Data stores
 It specifies relationship among components.
 It specifies software structures.
 Maintaines a record of design decision.
 Blueprint for the implementation phase.
 Design phase consist of
 Architectural design
 Detailed design

Architectural design:
 It involves identifying the software components
dividing them into software modules and conceptual
data structures, specifying interconnection among
components.
Detailed design
 It is concerned with the details of “how to”
 Package the processing modules.
 Implement the processing, algorithm, data structures
and interconnection among modules.

Implemention phase:
 It involves translation of design specification into
source code and debugging, documentation and unit
testing of source code.
Errors:
Implementation phase may include errors in routines,
functions, logical errors, and algorithm, errors in data
structure layout.

System testing:
It involves 2 kinds of activities
 Integration testing
 Acceptance testing
Integration testing:
Developing a stratedy for intergrating the software
components into a function requires careful planning
so that modules are available for integration when
needed.

Acceptance testing:
It involves planning an execution of various type of test
that software system satisfied requirements documents.
After getting the acceptance from the customer software
system of released for production work and mainteance
phase.
Mainteance Phase:
 It Includes
 the enchancement of capabilities.
 Adaptation of software to new processing environment.
 correction of software bugs.

Milestones, documents and reviews:
 Another view of the software lifecycle g softwareive
importance to the milestones, documents and reviews.
 Ask the software products evolves through the
development phase it is difficult for themanager and
team members to determine resources extended to
predict schedule delays extra.
 Establishing milestones, reviews points, documents
and management sign offs can improve project
visibility.
.

The development process becomes more public
activity and tangible.
 This result is improved
 Product quality
 Increased programmer productivity.
 Better moralae among team members

A system definition and project plan:
Product fesability review(PFR)
 PFR is held to determine the feasibility to project
continuation.
 The outcome of review may be
 Termination of the project.
 Redirection of the proect.
 Or continuation of the project as planned.

A primilarly version of the user’s manual is
prepared:
It involves a vehicle of communication between
customer and developer.
It is prepared using information from the system
definition and result of prototype studies and mock
ups of user displays and reports.

A software requirements specification is prepared:
 It defines each essential requirements for software
Product.
 External interface to software ,hardware, firm ware,
people subsystem.
 Each requirements should be define show that it can
be verified by a methods such as
 Inspection
 Demonstration
 Analysis or testing

primilarly version of the software verification of
the plan is prepared
 It states the methods to be used
 Results to be obtained.
A software requirements reviews(SRR)
 Is held to make sure the adequacy of
 system definition
 project plan
 software requirements specification
 software verification plan
 preliminary user’s manual.

Software design specification:
 The design team creates this specification in two stages
 Architectural design document is created.
 Following that the preliminary design review is held
then the detailed design specification is generated.
A preliminary design review(PDR)
 Is held to evaluate of adequacy of the architectural
design insatisfying the SPS(software Product
specification)
 Another reviews may be required to resolve problems
under format sign offs is required of the project manager.

Critical design review:
 Is held
 CDR is used determine the acceptablility of the software
design specification.
 A format sign offs is required.
During the design phase , the software verification
plan is expanned to include method:
 To verify that the design is complete and consistent with
respect to the requirements.
 To verify that the source code is complete and consistent
with respect to the requirements and design specification.

A software verification review is held to evaluate
the adequacy and completeness of the verification
plan:
 To review the primilinary acceptance test plan(ATP)
 ATP includes
 Actual test cases
 Expected result.
 Capabilities to be demonstrated by each test.
 The acceptance plan is initiated during the design
phase and completed during the implementation.

During the implementation phased:
 Source code is written.
 Debug.
 Unit tested.
 Standard parcties in the following area
 Logical structure
 Coading style
 Data layout
 Comments
 Debugging
 Unit testing

Source code reviews are held during
implementation:
 This is to ensure that all the code has been reviewed
by atleast one person other than programmer.
 Inspection are conducted during product evaluation
to verify the completeness, consistency and suitability
of the work products.
 The users manual the installations and training plans
and the software maintenance plans are completed
during the implementation phase.
A final acceptance review is performed prior to
product delivery’.

Software verification summary is prepared.
 It describes the results of all the reviews,
audits,inspection and test throughout the development
cycle.
A project legancy is written:
 The legancy summarises the project and provides a
record of what went well and what went wrong during
the project.

The cost model:
 This model is used specify the cost of performing
various activities in a Software project.
 The cost of conducting a Software project is the sum
of the cost involved in conducting each phase of the
project.
The cost involved each phase include:
 The cost of performing the process
 Preparing the products of the phase.
 Plus the cost of verifying the product of the present
phase are complete and consistent with the previous
phase.

Cost of producing system definition and project plan
=performing planning functions and preparing
documents+ cost of verifying the system definition and
project plan.
 Cost of SRS= Cost of requirements definition and
document + Cost of modifying system definition and
project plan + Cost of verifying SRS is complete and
consistence.
 Cost of design= Cost of preparing design specification
and test plan+ Cost of modifying and correcting the
system definition, project, SRS(Software requirement
specification)+cost of verifying design

Cost of product implementation= Cost of implementing
documenting, debugging and unit tesing of source code+ Cost
of users manual, verification plan, maintenance procedure,
instalization and tranning instructions+ Cost of modifying and
correcting system definition, project plan,SRS, design
specification, verification plan+the Cost of verifying the
implementation is complete and consistent.
 Cost of system test= Cost of planning and conducting the
test+ Cost of modifying and correcting the source code+ Cost
of verifying the test.
Cost of maintenance Software= Cost of performing product
enhancement +making adaptation to new processing
requirements and fixing bugs.

The prototype lifecycle model:
 Importance to the sources of product request , go/no go
decisions points and the use of the prototypes.
 Prototype is a mock up or model of the Software product.
 A prototype incorporates components of the actual model.
 There are several reasons for developing a prototype.
Important reason:
 It illustrates input data formats, messages, reports and
interactive dialogues for the customer.
 To explore technical problems in the proposed system.
 In situations where phased model of analysis, design,
implementation is not appropriate.

Successive version:
 Product development by the mothod of successive
versions is an extension of prototyping.
 In which an initial products skeleton is refined in to
increasing the level of capabilities
 It illustrates the analysis phase followed by
interactive design, implementation and assessment of
successive version.
 The dashed line indicates that the assessment of
version I may indicate the need for the further analysis
before designing version I+1.

Version I is the prototype version of the software
product.
 Versions one through N of the product or designed
prior to any implementation activities.
 The dashed line indicates that implementation of the
Ith version may reveal the need for further analysis
snd design before proceeding with implementation of
version I+1

Planning an organizational structure:
 Contains various task
 The task include
 Planning
 Product development
 Services
 Publications
 Quality assurance
 Support and maintenance

Planning task identifiers:
 External cutomers
 Internal product needes
 Conducts feasibility study.
Development Task Identifiers:
 design
 implements debuggs
 test and integrate the product

service task provides:
 automated tools and computer resources for all other
task. Performs configuration.
 Product distribution
Publication task develops:
 Users manual
 Instalization instruction Principles of operation
Supporting documents

Quality assurance task provides:
 Independent evaluvation of source code.
 Publications prior to releasing them to customer.
Support task:
 Promotes the product. Trainers user.
 Installs the product.
Maintenance task provides:
 Error connection Enhancement

Methods for organizing these task include:
 Project format
 Functional format
 Matrix format

Project structures
Project format
 It involes assuming a team of programmers. Project
team members do
 Product definition
 Design the product
 Implement it
 Test it
 Conducts Project review
 Preparing supporting document.

Functional format:
 In this approach a different team of programmers
perform each phase of the Project
 The work products pass from team to team as they
evolved
 Functional format involves 3 teams
 An analysis team.
 A design team and implementation team.
 test formatting and maintenance team.

Matrix format
 In this format each of the functions has its own management
team.
 This format involves a group of specialist personnel
concerned only with that function.
 Each development project has a project manager concerned
only with that Project
 The Project manager generates and reviews documents.
 Each functional group participate in each Project
 Ex: software development team members belongs to the
development function similarly testing belong the testing
function.

Programming team structure:
Every programming team must have an internal
structure.
Team structure depends on the nature of the Project
and the product
Basic team structure includes
Demacratic team
All team members participate in all decisions.

The chief programmer team:
 chief programmer is assited and supported by other
team members.
 Ex: doctors, surgeon
Hierarchical team:
 In combines the aspects of the democratic team and
chief programmer team.
 Each team should be limited to not more than 5 or 17
members for effective coordination and
communication.

Democratic team
 this teams was first described as egoless team.
 Group leadership rotates from member to member
based on the task to be performed and the differing
abilities of the team members.
 A Democratic team differs from an egoless team is
that one team members is designsted as team leader
and occupies the position of first among equals.
 This is because a team fuctions best when one
individual is responsible for coordinationg team
activities and for making final decision.

Advantages:
 Opptunities for each team members to contribute to
decision.
 To learn from one another
 Increased job satisfaction
 Non threatening work environment.
Disadvantages:
 Weeknening of individual and authority.
chief programmer teams:
this teams are highly structured.
 the chief programmer

design the product.
 Implement critical parts of the product
 Makes all the major technical decision.
 Work is allocated to the individual programmer by
the chief programmers.
 A program librarian maintains program listing,
design documents, test plans etc in a central location.
 The chief programmer is assited by an administrative
program manager.

Advantages:
 Centralized decision making.
 Reduced communication paths.
Hierarchical team structure:
 This structure occupies a middle position between the
extremes of Democratic teams and chief programmer
teams.
 The Project needed assigns, task, attends,
reviews,detects problem areas, balances the word load the
participate in technical activities.
 This structure limits the number of communication paths
in the Project

Disadvantages:
 The most technical competetant programmer tend to
be promoted in to management positions.
Promotion of the best programmer have the two
negative effects.
Losing a good programmer.
Creating a poor manager.
Other planning activities:
 Planning for configuration management and quality
assurance.

Configuration management:
Modeof arrangement
Concerned witj controlling changes in the work
products.
Accounting for the status of the work products
Mainteaning the program support library
Quality assurance:
Develops and monitors the Project standars.
Performs audits.
Develop and perfoms acceptance test.

During planning phase:
 The two activities are specified.
 Tools are identified an acquired.
During design phase:
 Requriments and design specification are performed.
 Adherence to project standard is monitor.
During implementation phase:
 Requirements, design specification and source code are
perfomed .
 During testing phase:
 Acceptance and preparation of test results are
performed.

Planning for independent verification and validation:
 An independent organization may provide verification of
work products for some critical software Project
 Veification makes sure that various work products are
complete and consistence.
 An external organization may verify that the design
specification are complete and cosistance.
 Source code is complete.
 Validation involves.
 Planning and execution of text cases.
 Independent verification and validation results in high
quality software product.

Planning phase-dependent tools and technique:
Automated tools,specialized notation and modern
techniques are used to develop software requriments
specification, architectural and detailed design and the
source code.
Management tools such as structures, charts, are used
to track and control progress.

Other planning activities:
 It includes:
 primilinary cost estimate.
 primilinary development schedule
 primilinary staffing levels.
 primilinary estimates of the computing resources and
personnel require to operate and maintain the system.

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