srs presenation by group 6

Software Requirements:Are They Really A Problem?

Author:Author:

T. E. Bell and T. A. ThayerT. E. Bell and T. A. Thayer

TRW Defense and Space Systems, Group Redondo Beach, California

Presented by Group 5

Humayun Kayesh ShamolHumayun Kayesh Shamol BIT-0114BIT-0114 Md. Iftekharul Alam EfatMd. Iftekharul Alam Efat BIT-0115BIT-0115 Mohammad IbrahimMohammad Ibrahim BIT-0117BIT-0117 Asif Imran AnikAsif Imran Anik BIT-0119BIT-0119 Amit Seal AmiAmit Seal Ami BIT-0122BIT-0122 Mirza Rehnuma TabassumMirza Rehnuma Tabassum BIT-0129BIT-0129

January 29, 2015 2Software Requirement Specification

& Analysis

Outline:

IntroductionIntroduction Software RequirementsSoftware Requirements Characteristics of RequirementsCharacteristics of Requirements

Empirical DataEmpirical Data Data LimitationsData Limitations Small System CaseSmall System Case Large System CaseLarge System Case


& Analysis

Definition:

Software requirements are requirements or Software requirements are requirements or required activities which are essential for software required activities which are essential for software project development.project development.

To derive the requirements we need to have clear To derive the requirements we need to have clear and thorough understanding of the products to be and thorough understanding of the products to be developed. This is prepared after detailed developed. This is prepared after detailed communications with project team and the communications with project team and the customer.customer.


& Analysis

Characteristics of Requirements


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Why software requirements are needed:

Effective requirements are very essential Effective requirements are very essential for effective software project.for effective software project.

The problems caused by incorrect software The problems caused by incorrect software requirement are often not identified at all.requirement are often not identified at all.


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Approaches of software requirement process:


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Development Phases of the SystemDevelopment Cycle


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Empirical Data:

Derived from experiment and observation Derived from experiment and observation

rather than theoryrather than theory

Information documented during the projectInformation documented during the project

Data collected during the project through Data collected during the project through

observationobservation


& Analysis

Problem Report:

Requirement deficiencies are written in the Requirement deficiencies are written in the problem reportsproblem reports

They are used to record the results of They are used to record the results of reviews or to request changesreviews or to request changes

Problem reports do not generally document Problem reports do not generally document the correction of deficiencies but they do the correction of deficiencies but they do record the symptoms of the problemrecord the symptoms of the problem


& Analysis

Sources of Problem Reports


& Analysis

Sources of Problem Reports:

Most of the problem reports are generated Most of the problem reports are generated during reviews, during design and during during reviews, during design and during implementationimplementation

The same software requirements deficiency The same software requirements deficiency may be identified at any of several points in may be identified at any of several points in the project life the project life


& Analysis

Data Limitation


& Analysis

Data Limitations

in

Software Requirement Problems report


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Limitations:

Develop project in undisciplined manner Develop project in undisciplined manner

Need for interpretation of textual materialsNeed for interpretation of textual materials

Insufficient information about the problems Insufficient information about the problems causescauses


& Analysis

Apparently no problem in Apparently no problem in requirement existsrequirement exists


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Can't interpret problems into a Can't interpret problems into a general classified schemegeneral classified scheme


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Abstracting from unspecified Abstracting from unspecified problem statementproblem statement““Something is wrong”Something is wrong”


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The Main ProblemThe Main Problem

Not concerned about reason of problems Not concerned about reason of problems in requirementin requirement


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Small System Case

Chosen because:Chosen because: Environment can be controlledEnvironment can be controlled Observation of outcomes is possibleObservation of outcomes is possible Easily understandable system decisionsEasily understandable system decisions


& Analysis

The Small System Case

A class divided to two teams by Dr. BoehmA class divided to two teams by Dr. Boehm Requirements TeamRequirements Team Design TeamDesign Team

All students received same All students received same

““Needs Statement”.Needs Statement”.


& Analysis


& Analysis

Small System Case

Student Employment Information SystemStudent Employment Information System accept and store information about accept and store information about

students' job qualifications and students' job qualifications and interestsinterests

employers' available openingemployers' available opening provide timely responses to students' provide timely responses to students'

or employers' job-matching queriesor employers' job-matching queries


& Analysis

Small System Case

• Student Employment Information SystemStudent Employment Information System– track the progress of outstanding job track the progress of outstanding job

offersoffers– provide summary information on the provide summary information on the

job market to appropriate UCLA job market to appropriate UCLA administratorsadministrators


& Analysis

The progress

Both teams met their time limits.Both teams met their time limits. Both Both informalinformal and formal meetings took and formal meetings took

place between themplace between them Record the problems by form (RPR)Record the problems by form (RPR)


& Analysis


& Analysis

What happened in Observation…

• Design team prepared Design team prepared – two designstwo designs

– Manual methodManual method• Batch data processing systemBatch data processing system

• Noticeable factor:Noticeable factor:– Design team estimated a cost which is Design team estimated a cost which is

about half the original costabout half the original cost


& Analysis

Impressive (?) Requirements Document According to some senior TRW personnelAccording to some senior TRW personnel

Superior to most documentsSuperior to most documents More problem specificMore problem specific DirectDirect CompleteComplete


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Analyzing Document in Detail

20 RPR used by design team20 RPR used by design team 32 Problems in reality32 Problems in reality

Estimated number of problems: 50 (by Estimated number of problems: 50 (by Boehm)Boehm)

Still an underestimationStill an underestimation


& Analysis


& Analysis

Classification of Found Problems

Design team made 23 classificationsDesign team made 23 classifications Authors made 32 classificationsAuthors made 32 classifications Different definitions of classification by Different definitions of classification by

author and design teamauthor and design team Inconsistency-ambiguityInconsistency-ambiguity Design constraining – Incorrect Design constraining – Incorrect

requirementrequirement


& Analysis

Analyzing the Case

Most common problems are:Most common problems are: AmbiguousAmbiguous Design constrainingDesign constraining

Statistically total number of problems seems Statistically total number of problems seems to be in excess of one (and probably in to be in excess of one (and probably in excess of two) times the number of pages in excess of two) times the number of pages in the requirements document.the requirements document.


& Analysis

Large System Case


& Analysis

Ballistic Missile Defense(BMD)


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Requirement Review:

1 million machine instructions1 million machine instructions

B-5 DocumentB-5 Document

Configuration Control Board (CCB)Configuration Control Board (CCB)

Classification of software error traceabilityClassification of software error traceability

STP development techniquesSTP development techniques


& Analysis

Comparison:

Software Requirements Problems Early STP Experience (1973)

Software Requirements Problems Recent STP Experience (1975)


& Analysis

Sample Requirement:


& Analysis

January 29, 2015Software Requirement Specification

& Analysis38

Problem Strategy:

Categories 1-000 & 6-000Categories 1-000 & 6-000: register acceptable : register acceptable changeschanges

Category 2-000Category 2-000: violates technical & contractual : violates technical & contractual boundariesboundaries

Total of 722 problems reports & 972 unique Total of 722 problems reports & 972 unique requirements out of 8248 general requirement requirements out of 8248 general requirement (support paragraphs in the 2500 pages)(support paragraphs in the 2500 pages)


& Analysis

Findings:

A huge number of requirementsA huge number of requirements

Details requirement for proper developmentDetails requirement for proper development

Change of requirement during project Change of requirement during project

lifetimelifetime

Good planning helps to reduce requirementGood planning helps to reduce requirement


& Analysis

Requirement Challenges:

Difficult to control development environmentDifficult to control development environment Long development timeLong development time Large number of participantsLarge number of participants Complex requirement specifications & analysis Complex requirement specifications & analysis

phasephase Large number of variables & control functionLarge number of variables & control function Less supporting documentsLess supporting documents


& Analysis

Reasons for Changing Requirements:

External reasonsExternal reasons Social & political factorsSocial & political factors Change in business & technological Change in business & technological

environmentenvironment Internal reasonsInternal reasons

Better understanding of functionalityBetter understanding of functionality Marketing & other business viewpointsMarketing & other business viewpoints


& Analysis

Categories of Requirement Problems:

MissingMissing InadequateInadequate UnclearUnclear IncompleteIncomplete AccuracyAccuracy Criteria absentCriteria absent


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Quantity of Problems:

Sheer volume of problems encounteredSheer volume of problems encountered

Difficult to prioritize requirements due to large sizeDifficult to prioritize requirements due to large size

Unclearness in classification & organizationUnclearness in classification & organization

Difficult to document & keep track of the Difficult to document & keep track of the

requirementsrequirements

Failure to identify critical problemsFailure to identify critical problems


& Analysis

Ways to Solve Problems:

Good understandabilityGood understandability

Better organization & classificationBetter organization & classification

Resolving conflicts timelyResolving conflicts timely

Documenting requirementsDocumenting requirements

Use of requirement management software toolsUse of requirement management software tools


& Analysis

Critical Review Certain methods are outdated that have already been dealt Certain methods are outdated that have already been dealt

withwith Modules of data collection techniques deemed Modules of data collection techniques deemed

replaceablereplaceable Negligible use of Requirements Management ToolsNegligible use of Requirements Management Tools Requirement gathering methods like RPR replaceableRequirement gathering methods like RPR replaceable Manual documentation replaced by automated toolsManual documentation replaced by automated tools No mentioned use of case toolsNo mentioned use of case tools RMT has already replaced CCB mentioned hereRMT has already replaced CCB mentioned here Instant Retrieval of information have become automatedInstant Retrieval of information have become automated

Critical Review(continued)

Requirements traceability is automatedRequirements traceability is automated Change management process has become Change management process has become

automatedautomated Manual storage of data is outdatedManual storage of data is outdated Identification of critical requirements have Identification of critical requirements have

become automated as wellbecome automated as well


& Analysis

srs presenation by group 6

Technology