Requirements Documentation 2005

8/18/2019 Requirements Documentation 2005

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%rob(ems in #e-e(o'ing com'uterbase# systems since 1./0s

&oo many systems are (ate or o-er bu#get

Systems #ont #o what the users rea((y want orne-er use# to the effecti-eness

there are rare(y a sing(e reason for these 'rob(emsbut a ma,or contributory factor is #ifficu(ties withsystem requirements2


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hat are requirements4

A s'ecification of what shou(# be im'(emente#

Define# at ear(y stages of a system #e-e(o'ment

"nc(u#e5

how the system shou(# beha-e

a''(ication #omain information

constraints on the systems o'eration

s'ecification of a system 'ro'erty or attribute6


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hat is requirements engineering4

A re(ati-e(y new term in-ente# to co-er a(( of theacti-ities in-o(-e# in #isco-ering #ocumenting an#maintaining a set of requirements for a com'uter*base# system6

8se of the term engineering im'(ies thatsystematic an# re'eatab(e techniques shou(# be

use# to ensure that system requirements arecom'(ete consistent an# re(e-ant6


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9ow much #oes requirementsengineering cost4

De'en#s on the ty'e an# size of the system being#e-e(o'e#

"n a sur-ey for (arge har#ware:software systemsabout 1!; of the tota( bu#get is ta


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Common requirements 'rob(ems

Dont ref(ect the rea( nee#s of the customers

"nconsistent an# incom'(ete

$='ensi-e to maisun#erstan#ings between customers those#e-e(o'ing the system requirements an# softwareengineers


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hat is a requirements engineering'rocess4

Requirements engineering 'rocess is a structure# setof acti-ities which are fo((owe# to #eri-e -a(i#ate an#maintain a systems requirements #ocument6 &heacti-ities inc(u#e5

Requirements e(icitation

Requirements ana(ysis an# negotiation

Requirements #ocumentation

Requirements -a(i#ation


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Requirements e(icitation techniques

&he system requirements are #isco-ere# throughconsu(tation with sta


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"nter-iews

C(ose# (oo'5 inter-iewer (oo


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Scenarios

Stories of how the system wi(( be use#

$n#*users an# other sta


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An e=am'(e scenario

Scenario of or#ering a re'ort from a (ibrary5

&he user (ogs on the system

&he or#er #ocument is issue#

&he reference number of the #ocument is entere#

A #e(i-ery o'tion is se(ecte#

&he user (ogs out6

$=ce'tion5 if the reference number is incorrect the user isoffere# to enter the #ocument reference or in-o


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Requirements Reuse

A goo# 'ractice to reuse as much


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%rototy'ing

An initia( -ersion of the system which is a-ai(ab(eear(y in the #e-e(o'ment 'rocess

9e('s e(icit an# -a(i#ate the system requirements

throw*away 'rototy'es use# to he(' e(icit an#ana(yze the requirements are often ca((e#

"n contrast e-o(utionary 'rototy'es are inten#e# to#e(i-er a wor


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%rototy'ing – cont@#

%rototy'es he(' to estab(ish the o-era(( feasibi(ityan# usefu(ness of the system

&he on(y effecti-e way of #e-e(o'ing system userinterface6

>ay be 'ossib(e to be use# in system tests (ater in

the -a(i#ation 'rocess


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Requirements ana(ysis an#negotiation

Aim at #isco-ering 'rob(ems with the systemrequirements an# reach agreement on changes tosatisfy a(( system sta


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Ana(ysis chec


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"nteraction matrices

8se# to #isco-er the interactions betweenrequirements an# to high(ight requirementsconf(icts an# o-er(a's

"f we can not assume that conf(icts #o not e=ist weshou(# assume that there is a 'otentia( conf(ict

8n#etecte# conf(icts are much more e='ensi-e toreso(-e


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$=am'(e – "nteraction matrices

+5 +)$RA%

C5 C+?F"C&

Requirement R1 R2 R3 R4 R5 R6

R1 - - O - C C

R2 - - - - - -

R3 O - - O - O

R4 - - O - C C

R5 C - - C - -

R6 C - O C - -


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Requirements negotiation

Discussing conf(icts an# fin#ing some com'romise which a((of the staeetings are most effecti-e way6 >eetings shou(# be

con#ucte# in three stages5

An information stage e='(aining the nature of the 'rob(em

A #iscussion stage in which sta


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Requirements Documentation

&here are many #ifferent ways to structure therequirements #ocuments #e'en#ing on5

&he ty'e of the system being #e-e(o'e#

&he (e-e( of #etai( inc(u#e#

+rganizationa( 'ractice

Bu#get

Sche#u(e


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Stan#ar# &em'(ates

$nsures that a(( the essentia( information is inc(u#e#

A number of #ifferent (arge organizations such as the 8S De'artmentof Defense an# "$$$ ha-e #efine# stan#ar#s for requirements#ocuments

%robab(y the most acce'tab(e of these stan#ar#s is the "$$$:A?S" 30*1..3

&he stan#ar# recognizes #ifferences between systems an# a((ows forsome -ariations in the structure6

&here is a (ist of stab(e an# -ariant 'arts5

Stab(e 'arts

)ariant 'arts


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"$$$:A?S" 30 * 1..3 Introduction:

%ur'ose of the requirements #ocument

Sco'e of 'ro#uct

Definitions acronyms an# abbre-iations

References

+-er-iew of the remain#er of the #ocument

General Description: %ro#uct 'ers'ecti-e

%ro#uct functions

8ser characteristics

enera( constraints

Assum'tions an# #e'en#encies


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"$$$:A?S" 30 – 1..3 – cont@#

S'ecific requirements

Co-ering functiona( non*functiona( an# interfacerequirements6 &hese shou(# inc(u#e e=terna(

interfaces functiona(ity 'erformance requirements(ogica( requirements #esign constraints systemattributes an# qua(ity characteristics

A''en#ices

"n#e=


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A tem'(ate base# on "$$$:A?S"30 – 1..3

%reface

"ntro#uction Definition of the 'ro#uct its e='ecte# usage an# an

o-er-iew of its functiona(ity

(ossary Definition of technica( terms an# abbre-iations use#

enera( user requirements &he systems requirements from the 'ers'ecti-e of the user

System architecture A high*(e-e( o-er-iew of the antici'ate# system architecture

showing the #istribution of functions across system mo#u(es


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$=am'(e – cont@#

9ar#ware s'ecification +'tiona( 'art for s'ecifying of the har#ware that the software system is

to e='ecte# contro(

Detai(e# software s'ecification Detai(e# #escri'tion of the e='ecte# system functiona(ity

Re(iabi(ity an# 'erformance requirements Describes the re(iabi(ity an# 'erformance e='ecte#6

A''en#ices for 9ar#ware interface s'ecification

Software com'onents Data structures s'ecification Data*f(ow mo#e(s of the software system Detai(e# ob,ect mo#e(s of the software system

"n#e=


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Requirements -a(i#ation

&he 'rocess out'uts are as fo((ows5

A (ist of 'rob(ems

Agree# so(ution

&echniques for requirements -a(i#ation5

Requirements re-iews5 "n-o(-es a grou' of 'eo'(e who rea#an# ana(yze the requirements

%re*re-iew chec


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8ser manua( #e-e(o'ment 8ser manua( #e-e(o'ment5

Rewriting the requirements in a #ifferent way is a -ery effecti-e -a(i#ationtechnique6

&o rewrite the #ocument you must un#erstan# the requirements an# there(ationshi's6

De-e(o'ing this un#erstan#ing re-ea(s conf(icts omissions an#inconsistencies6

A user manua( shou(# inc(u#e the fo((owing information5

A #escri'tion of the functiona(ity an# how to access the functiona(ity throughthe user interface

A #escri'tion of how to reco-er from #ifficu(ties

"nsta((ation instructions for users


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Actors in requirements engineering'rocess

Domain e='ert5 'ro-i#e information about the a''(ication#omain an# the s'ecific 'rob(em in that #omain which is to beso(-e#

System en#*user5 wi(( use the system after #e(i-ery

Requirements engineer5 e(iciting an# s'ecifying therequirements

Software engineer5 res'onsib(e for #e-e(o'ing the software

system

%ro,ect manager5 '(anning an# estimating the 'rototy'ing'ro,ect


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Structure# Ana(ysis an# Design&echnique SAD&2

De-e(o'e# in the (ate 1.70s by Ross

Base# on #ata*f(ow mo#e(s that -iew the system as aset of interacting acti-ities

Decom'oses the 'rob(em into a set of hierarchica(#iagram each com'ose# of a set of bo=es an# arrows

$ach (ower (e-e( is #ocumente# se'arate(y an#re'resents the refinement to the 're-ious (e-e(

&he most abstract (e-e( is the conte=t #iagramre'resenting the systems acti-ities with a set ofin'ut:out'uts6


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SAD& -iew'oints

SAD& #oes not ha-e an e='(icit notion of-iew'oints -iew'oints are an intuiti-e e=tension

AC&")"&E

Contro(

>echanism

+ut'ut"n'ut


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$=am'(e

"ssue (ibraryitem

ibrary car#

Return Date

Requeste# "tem

"ssue# item ibrary 8serG"ssue c(er


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$=am'(e – cont@#

8ser #atabase

ibrary Car#

"tem #atabase

Chec< user

Chec< item

"ssue item

Requeste# item

Return #ate

8ser #etai(

8ser status

8'#ate #etai(s

"ssue# item

"tema-ai(abi(ity

"tem status

Chec


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)iew'oint*oriente# System$ngineering )+S$2

De-e(o'e# in "m'eria( Co((ege on#on in ear(y1./0s

)+S$ is a framewor< that a##resses the entiresystem #e-e(o'ment cyc(e

8ses #ata*f(ow an# state transition scheme tomo#e( the system wor(#

Requires further e=amination of consistencybetween #ifferent -iew'oints


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$=am'(e – a )+S$ state transition

+ff*#es<

Chec


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8se cases

8se# in ++ Ana(ysis

Definition

Describes the sequence of e-ents of some ty'es of usersactors2 using some 'art of system functiona(ity tocom'(ete a 'rocess

Actors5 A 'erson organization or e=terna( system'(aying a ro(e in some interactions with the system

Associations5 interactions between actors an# use cases


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8se cases – e=am'(e

Actor action System response16 &his use case begins when a Customer

arri-es at a %+S& chec


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8se cases – e=am'(e – cont@#

/6 &he Cashier te((s the Customer the

tota(6

76 &he Customer gi-es a cash 'ayment'ossib(y greater than the sa(e tota(6

6 &he Cashier recor#s the cash recei-e#

amount6

.6 Shows the ba(ance #ue bac< to the

Customer6 enerate a recei't6106 &he Cashier #e'osits the cash

recei-e# an# e=tracts the ba(ance owing6

116 ogs the com'(ete# sa(e6 &he Cashier

gi-es the ba(ance owing an# the 'rinte#recei't to the Customer6

16 &he Customer (ea-es with the items

'urchase#6

Alternative Courses I ine 75 Customer #i#n@t ha-e enough cash6 Cance( sa(es

transaction


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8se Cases Diagrams in 8>

8se cases – horizonta( e((i'ses

Actors – stic< figures

Associations – (ines the arrowhea# in#icates the#irection of initia( in-ocation2

System boun#ary bo= o'tiona(2


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A sim'(e use case #iagram


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Common 'rob(ems in writingrequirements

Requirements are written in com'(e= con#itiona(c(auses which are confusing

&ermino(ogy is use# in a s(o''y an# inconsistentway

&he writers of the requirement assume that the

rea#er has s'ecific


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&hings that the writer shou(# bearin min#

Requirements are rea# more often than they arewritten6 "n-est more effort to write #ocuments thatare easy to rea# an# un#erstan#

Rea#ers of requirements come from #i-ersebac


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ui#e(ines

Define stan#ar# tem'(ates for #escribingrequirements

8se (anguage sim'(y concise(y an# consistent(y6 8seshort sentences an# 'aragra'hs

8se #iagrams a''ro'riate(y to 'resent o-er-iews an#re(ationshi's between entities

S'ecify requirements quantitati-e(y number of usersres'onse time requirements etc62


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Juestions

J1 – "#entify 10 functiona( system requirementsfor an on(ine uni-ersity (ibrary system6

J – rite use cases for the (ibrary system in J1an# #raw the use case #iagrams6

J3 – Draw state transition an# #ata*f(ow #iagramsfor the (ibrary system6


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References

Bahati Sanga Assessing an# im'ro-ing the qua(ity of softwarerequirements s'ecification #ocuments >c>aster 8ni-ersity 003

6 Kotonya Requirements $ngineering 'rocesses an# techniquesi(ey 1..7

R6S6 %ressman Software $ngineering a 'ractitioners a''roachFifth e#ition >craw*9i((

D6>6 Berry 8sers manua(s as a requirements s'ecification 003

Lhiming iu +b,ect*+riente# Software De-e(o'ment with

8> &he 8nite# ?ations 8ni-ersity Mu(y 00

9ow to Draw 8> 8se Case Diagrams by Scott 6 Amb(era-ai(ab(e on(ine athtt'5::www6agi(emo#e(ing6com:artifacts:useCaseDiagram6htm
http://www.agilemodeling.com/artifacts/useCaseDiagram.htmhttp://www.agilemodeling.com/artifacts/useCaseDiagram.htm

Documents

Requirements Documentation 2005