– 6 – 2016-05-12 – main –

Softw

aretech

nik

/Softw

are-E

ngin

eering

Lectu

re6:

Req

uirem

ents

Engin

eering

2016-0

5-1

2

Pro

f.Dr.A

nd

reas

Po

de

lski,Dr.B

ern

dW

estp

hal

Alb

ert-Lu

dw

igs-Un

iversität

Freib

urg,G

erm

any

Yo

uA

reH

ere.

– 6 – 2016-05-12 – main –

2/

37

Intro

du

ction

L1:

18.4

.,Mo

n

L2

:2

1.4.,

Th

uS

cales,M

etrics,

Co

stsL

3:

25

.4.,M

on

T1:

28

.4.,

Th

u

De

velo

pm

en

tL

4:

2.5

.,Mo

n

-5

.5.,

Th

u

Pro

cess

L5

:9

.5.,M

on

L6

:12

.5.,

Th

u

-16

.5.,M

on

-19

.5.,

Th

u

T2

:2

3.5

.,Mo

n

-2

6.5

.,T

hu

L7:

30

.5.,M

on

L8

:2

.6.,

Th

uR

eq

uire

me

nts

En

gine

erin

gL

9:

6.6

.,Mo

n

T3

:9

.6.,

Th

u

L10:

13.6

.,Mo

n

L11:

16.6

.,T

hu

Arch

itectu

re&

De

signL

12:

20

.6.,M

on

T4

:2

3.6

.,T

hu

L13

:2

7.6.,M

on

So

ftware

Mo

nd

ellin

gL

14:

30

.6.,

Th

u

L15

:4

.7.,Mo

n

T5

:7.7.,

Th

u

L16

:11.7.,M

on

L17:

14.7.,

Th

uQ

uality

Assu

rance

(Testin

g,Form

alV

erificatio

n)

L18

:18

.7.,Mo

nW

rap-U

pL

19:

21.7.,

Th

u

To

pic

Area

Req

uirem

ents

En

gin

eering

:C

on

tent

– 6 – 2016-05-12 – Sblockcontent –

3/

37

•In

trod

uctio

n

•R

eq

uire

me

nts

Sp

ecificatio

n

•D

esire

dP

rop

ertie

s

•K

ind

so

fR

eq

uire

me

nts

•A

nalysis

Tech

niq

ue

s

•D

ocu

me

nts

•D

iction

ary,Sp

ecificatio

n

•S

pe

cification

Lan

gu

ages

•N

aturalL

angu

age

•W

orkin

gD

efin

ition

:So

ftware

•D

ecisio

nTab

les

•S

yn

tax,Se

man

tics

•C

on

sisten

cy,Co

mp

lete

ne

ss,...

•S

cen

arios

•U

ser

Sto

ries,U

seC

ases

•Live

Se

qu

en

ceC

harts

•S

yn

tax,Se

man

tics

•D

iscussio

n

VL

6

...

VL

7

...

VL

8...

VL

9...

Reca

ll:S

tructu

reo

fTo

pic

Area

s

– 6 – 2016-05-12 – Sblockstruct –

4/

37

Exam

ple

:Re

qu

irem

en

tsE

ngin

ee

ringVo

cabu

larye

.g.con

sisten

t,co

mp

lete

,tacit,etc.

Tech

niq

ue

s

info

rmal

sem

i-form

al

form

al

Co

nten

t

– 6 – 2016-05-12 – Scontent –

5/

37

•In

trod

uctio

n

•V

ocab

ulary

:Re

qu

irem

en

ts(A

nalysis)

•U

sages

of

Re

qu

irem

en

tsS

pe

cification

s

•R

eq

uire

me

nts

Sp

ecificatio

n

•D

esire

dP

rop

ertie

s

•K

ind

so

fR

eq

uire

me

nts

•A

nalysis

Tech

niq

ue

s

•D

ocu

me

nts

•D

iction

ary

•S

pe

cification

•S

pe

cification

Lan

gu

ages

•N

aturalL

angu

age

Intro

du

ction

– 6 – 2016-05-12 – main –

6/

37

– 6 – 2016-05-12 – Sreintro –

8/

37

Th

eh

ard

estsin

glep

art

of

build

ing

aso

ftwa

resystem

isd

ecidin

gp

reciselyw

ha

tto

build

.

No

oth

erp

art

of

the

con

ceptua

lwo

rkis

as

difficult

as

estab

lishin

gth

ed

etailed

techn

ical

requirem

ents

...

No

oth

erp

art

of

the

wo

rkso

cripp

lesth

eresultin

gsystem

ifd

on

ew

ron

g.

No

oth

erp

art

isa

sd

ifficultto

rectifyla

ter.F.P.B

roo

ks(B

roo

ks,199

5)

Req

uirem

ents

Sp

ecifica

tion

s

– 6 – 2016-05-12 – main –

10/

37

Req

uirem

ents

An

alysis...

– 6 – 2016-05-12 – Sre –

11/3

7

...in

the

sen

seo

f“fin

din

go

ut

wh

atth

ee

xactre

qu

irem

en

tsare”.

“An

alysing

ane

xisting

req

uire

me

nts/

featu

resp

ecificatio

n”→

later.

Inth

efo

llow

ing

we

shalld

iscuss:

(i)d

esire

dp

rop

ertie

so

f

•re

qu

irem

en

tssp

ecificatio

ns,

•re

qu

irem

en

tssp

ecificatio

nd

ocu

me

nts,

(ii)kin

ds

of

req

uire

me

nts

•h

ardan

dso

ft,

•o

pe

nan

dtacit,

•fu

nctio

nalan

dn

on

-fun

ction

al.

(iii)(a

sele

ction

of)an

alysis

tech

niq

ue

s

(iv)d

ocu

me

nts

of

the

req

uire

me

nts

analysis:

•d

iction

ary,

•re

qu

irem

en

tssp

ecificatio

n(‘L

asten

he

ft’),

•fe

ature

spe

cification

(‘Pflich

ten

he

ft’).

•N

ote

:Inth

efo

llow

ing

(un

less

oth

erw

isen

ote

d),w

ed

iscuss

the

featu

resp

ecificatio

n,

i.e.th

ed

ocu

me

nt

on

wh

ichth

eso

ftware

de

velo

pm

en

tis

base

d.

Tom

aximise

con

fusio

n,w

em

ayo

ccasion

ally(in

con

sisten

tly)callitre

qu

irem

en

tssp

ecificatio

no

rju

stsp

ecificatio

n—

sho

uld

be

clear

from

con

text...

•R

ecall:o

ne

and

the

same

con

ten

tcan

serve

bo

thp

urp

ose

s;on

lyth

etitle

de

fine

sth

ep

urp

ose

the

n.

Req

uirem

ents

on

Req

uirem

ents

Sp

ecifica

tion

s

– 6 – 2016-05-12 – Sre –

12/

37

Are

qu

irem

en

tssp

ecificatio

nsh

ou

ldb

e

•co

rrect

—it

corre

ctlyre

pre

sen

tsth

ew

ishe

s/n

ee

ds

of

the

custo

me

r,

•co

mp

lete

—allre

qu

irem

en

ts(e

xisting

inso

me

bo

dy’s

he

ad,o

ra

do

cum

en

t,or

...)sh

ou

ldb

ep

rese

nt,

•re

levan

t—

thin

gsw

hich

aren

ot

rele

vant

toth

ep

roje

ctsh

ou

ldn

ot

be

con

straine

d,

•co

nsiste

nt,fre

eo

fco

ntrad

iction

s—

each

req

uire

me

nt

isco

mp

atible

with

alloth

er

req

uire

me

nts;o

the

rwise

the

req

uire

me

nts

aren

ot

realisab

le,

•n

eu

tral,abstract

—a

req

uire

me

nts

spe

cification

do

es

no

tco

nstrain

the

realisatio

nm

ore

than

ne

cessary,

•trace

able

,com

pre

he

nsib

le—

the

sou

rces

of

req

uire

me

nts

ared

ocu

me

nte

d,

req

uire

me

nts

areu

niq

ue

lyid

en

tifiable

,

•te

stable

,ob

jective

—th

efin

alpro

du

ctcan

ob

jective

lyb

ech

ecke

dfo

rsatisfy

ing

are

qu

irem

en

t.

•C

orre

ctne

ssan

dco

mp

lete

ne

ssare

de

fine

dre

lativeto

som

eth

ing

wh

ichis

usu

allyo

nly

inth

ecu

stom

er’s

he

ad.

→is

isd

ifficult

tob

esu

reo

fco

rrectn

ess

and

com

ple

ten

ess.

•“D

ear

custo

me

r,ple

asete

llme

wh

atis

iny

ou

rh

ead

!”is

inalm

ost

allcases

no

ta

solu

tion

!

It’sn

ot

un

usu

althat

eve

nth

ecu

stom

er

do

es

no

tp

recise

lykn

ow

...!

For

exam

ple

,the

custo

me

rm

ayn

ot

be

aware

of

con

tradictio

ns

du

eto

tech

nicallim

itation

s.

Req

uirem

ents

on

Req

uirem

ents

Sp

ecifica

tion

Do

cum

ents

– 6 – 2016-05-12 – Sre –

13/

37

Th

ere

pre

sen

tation

and

form

of

are

qu

irem

en

tssp

ecificatio

nsh

ou

ldb

e:

•e

asilyu

nd

erstan

dab

le,

no

tu

nn

ece

ssarilyco

mp

licated

—allaffe

cted

pe

op

lesh

ou

ldb

eab

leto

un

de

rstand

the

req

uire

me

nts

spe

cification

,

•p

recise

—th

ere

qu

irem

en

tssp

ecificatio

nsh

ou

ldn

ot

intro

du

cen

ew

un

clarities

or

roo

ms

for

inte

rpre

tation

(→te

stable

,ob

jective),

•e

asilym

aintain

able

—cre

ating

and

main

tainin

gth

ere

qu

irem

en

tssp

ecificatio

nsh

ou

ldb

ee

asyan

dsh

ou

ldn

ot

ne

ed

un

ne

cessary

effo

rt,

•e

asilyu

sable

—sto

rageo

fan

dacce

ssto

the

req

uire

me

nts

spe

cification

sho

uld

no

tn

ee

dsign

ificant

effo

rt.

No

te:O

nce

again,it’s

abo

ut

com

pro

mise

s.

•A

very

pre

ciseo

bje

ctivere

qu

irem

en

tssp

ecificatio

nm

ayn

ot

be

easily

un

de

rstand

able

by

eve

ryaffe

cted

pe

rson

.

→p

rovid

ere

du

nd

ant

exp

lanatio

ns.

•It

isn

ot

trivialtoh

aveb

oth

,low

main

ten

ance

effo

rtan

dlo

wacce

sse

ffort.

→valu

elo

wacce

sse

ffort

hig

he

r,a

req

uire

me

nts

spe

cification

do

cum

en

tis

mu

chm

ore

ofte

nre

adth

anch

ange

do

rw

ritten

(and

mo

stch

ange

sre

qu

irere

adin

gb

efo

reh

and

).

Pitfa

ll:Vag

uen

essvs.

Ab

stractio

n

– 6 – 2016-05-12 – Sre –

14/

37

Co

nsid

er

the

follo

win

ge

xamp

les:

•V

agu

e(n

ot

pre

cise):

“the

listo

fp

articipan

tssh

ou

ldb

eso

rted

con

ven

ien

tly”

•P

recise

,abstract:

“the

listo

fp

articipan

tssh

ou

ldb

eso

rted

by

imm

atriculatio

nn

um

be

r,low

est

nu

mb

er

first”

•P

recise

,no

n-ab

stract:“th

elist

of

particip

ants

sho

uld

be

sorte

db

y

publicstatic<T>voidCollections::sort(List<T>list,Comparatorc

);

wh

ere

Tis

the

typ

eo

fp

articipan

tre

cord

s,cco

mp

ares

imm

atriculatio

nn

um

be

rn

um

erically.”

•A

req

uire

me

nts

spe

cification

sho

uld

always

be

asp

recise

asp

ossib

le(→

testab

le,o

bje

ctive).

Itn

ee

dn

ot

de

no

tee

xactlyo

ne

solu

tion

;p

recise

lych

aracterisin

gacce

ptab

leso

lutio

ns

iso

ften

mo

reap

pro

priate

.

•B

ein

gto

spe

cific,may

limit

the

de

signd

ecisio

ns

of

the

de

velo

pe

rs,wh

ichm

aycau

seu

nn

ece

ssaryco

sts.

•Id

ealise

dvie

ws

advo

catea

strictse

paratio

nb

etw

ee

nre

qu

irem

en

ts(“w

hat

isto

be

do

ne?”)

and

de

sign

(“ho

ware

thin

gsto

be

do

ne?”).

Kin

ds

of

Req

uirem

ents

– 6 – 2016-05-12 – Sre –

15/

37

Kin

ds

of

Req

uirem

ents:

Fu

nctio

na

la

nd

No

n-F

un

ction

al

– 6 – 2016-05-12 – Sre –

16/

37

•P

rop

osal:V

iew

softw

areS

asa

fun

ction

S:i1,i2,i3,···

7→o0,o1,o2,...

wh

ichm

aps

seq

ue

nce

so

fin

pu

tsto

seq

ue

nce

so

fo

utp

uts.

Exam

ple

s:

•S

oftw

are“co

mp

ute

ship

pin

gco

sts”:

•o0

:initialstate

,

•i1

:ship

pin

gp

arame

ters

(we

ight,size

,de

stinatio

n,...),

•o1

:ship

pin

gco

sts

An

dn

om

ore

inp

uts,S

:i17→

o1

.

•S

oftw

are“traffic

lights

con

trolle

r”:

•o0

:initialstate

,

•i1

:pe

de

strianp

resse

sb

utto

n,

•o1,o2,...

:stop

traffic,givegre

en

top

ed

estrian

s,

•in

:bu

tton

pu

she

dagain

•...

•E

very

con

straint

on

thin

gsw

hich

areo

bse

rvable

inth

ese

qu

en

ces

isa

fun

ction

alre

qu

irem

en

t(b

ecau

seit

req

uire

sso

me

thin

gfo

rth

efu

nctio

nS

).

Th

us

timin

g,e

ne

rgy

con

sum

ptio

n,e

tc.may

be

sub

ject

tofu

nctio

nalre

qu

irem

en

ts.

•C

learly

no

n-fu

nctio

nal

req

uire

me

nts:

pro

gramm

ing

langu

age,co

din

gco

nve

ntio

ns,p

roce

ssm

od

elre

qu

irem

en

ts,po

rtability

...

Kin

ds

of

Req

uirem

ents:

Ha

rda

nd

So

ftR

equ

iremen

ts

– 6 – 2016-05-12 – Sre –

17/

37

•E

xamp

leo

fa

hard

req

uire

me

nt:

•C

ashin

ga

che

qu

eo

verNe

mu

stre

sult

ina

ne

wb

alance

de

crease

db

yN

;th

ere

isn

ot

am

icro-ce

nt

of

tole

rance

.

•E

xamp

les

of

soft

req

uire

me

nts:

•If

ave

nd

ing

mach

ine

disp

en

ses

the

sele

cted

item

with

in1

s,it’scle

arlyfin

e;if

ittake

s5

min

.,it’scle

arlyw

ron

g—

wh

ere’s

the

bo

un

dary?

•A

care

nte

rtainm

en

tsyste

mw

hich

pro

du

ces

“no

ise”(d

ue

tolim

ited

bu

sb

and

wid

tho

rC

PU

po

we

r)in

average

on

cep

er

ho

ur

isacce

ptab

le,o

nce

pe

rm

inu

teis

no

tacce

ptab

le.

Th

eb

ord

er

be

twe

en

hard

/so

ftis

difficu

ltto

draw

,and

•as

de

velo

pe

r,we

wan

tre

qu

irem

en

tssp

ecificatio

ns

tob

e“as

hard

asp

ossib

le”,

i.e.w

ew

ant

acle

arrigh

t/w

ron

g.

•as

custo

me

r,we

ofte

ncan

no

tp

rovid

eth

isclarity

;w

ekn

ow

wh

atis

“ clearly

wro

ng

”an

dw

ekn

ow

wh

atis

“clearly

righ

t”,bu

tw

ed

on’t

have

ash

arpb

ou

nd

ary.

→in

tervals,rate

s,etc.can

serve

asp

recise

spe

cification

so

fso

ftre

qu

irem

en

ts.

Kin

ds

of

Req

uirem

ents:

Op

ena

nd

Ta

cit

– 6 – 2016-05-12 – Sre –

18/

37

•o

pe

n:cu

stom

er

isaw

areo

fan

dab

leto

exp

licitlyco

mm

un

icateth

ere

qu

irem

en

t,

•(se

mi-)tacit:

custo

me

rn

ot

aware

of

som

eth

ing

be

ing

are

qu

irem

en

t(o

bvio

us

toth

ecu

stom

er

bu

tn

ot

con

side

red

rele

vant

by

the

custo

me

r,no

tkn

ow

nto

be

rele

vant).

Exam

ple

s:

•b

utto

ns

and

scree

no

fa

mo

bile

ph

on

esh

ou

ldb

eo

nth

esam

esid

e,

•im

po

rtant

we

b-sh

op

item

ssh

ou

ldb

eo

nth

erigh

th

and

side

be

cause

the

main

use

rsare

socialise

dw

ithrigh

t-to-le

ftre

adin

gd

irectio

n,

•th

eE

CU

(em

be

dd

ed

con

trolu

nit)m

ayo

nly

be

allow

ed

use

ace

rtainam

ou

nt

of

bu

scap

acity.

An

alyst

kno

ws

do

main

ne

wto

do

main

Customer/Clientexplicit

req

uire

me

nts

disco

vere

dre

qu

irem

en

tsd

iscove

rable

semi-tacit

req

uire

me

nts

disco

verab

le

req

uire

me

nts

disco

verab

lew

ithd

ifficultie

s

tacit

hard

/im

po

ssible

tod

iscove

r

(Gacitu

ae

tal.,2

00

9)

•d

istingu

ishd

on

’tcare

:

inte

ntio

nally

left

op

en

tob

ed

ecid

ed

by

de

velo

pe

r.

Req

uirem

ents

An

alysis

Tech

niq

ues

– 6 – 2016-05-12 – main –

19/

37

(AS

election

of)

An

alysis

Tech

niq

ues

– 6 – 2016-05-12 – Sreana –

20

/3

7

Focu

scu

rren

td

esire

din

no

vation

An

alysis

Tech

niq

ue

situatio

nsitu

ation

con

seq

ue

nce

s

An

alysiso

fe

xisting

data

and

do

cum

en

ts

Ob

servatio

n

Qu

estio

nn

ing

with

(

close

dstru

cture

do

pe

n

)

qu

estio

ns

Inte

rview

Mo

de

lling

Exp

erim

en

ts

Pro

toty

pin

g

Particip

atived

eve

lop

me

nt

(Lud

ew

igan

dLich

ter,2

013

)

Req

uirem

ents

Elicita

tion

– 6 – 2016-05-12 – Sreana –

21/

37

•O

bse

rvation

:

Cu

stom

ers

cann

ot

be

assum

ed

tob

etrain

ed

instatin

g/co

mm

un

icating

req

uire

me

nts.

•It

isth

etask

of

the

analy

stto

:

•ask

wh

atis

wan

ted

,ask

wh

atis

no

tw

ante

d,

•e

stablish

pre

cision

,lo

ok

ou

tfo

rco

ntrad

iction

s,

•an

ticipate

exce

ptio

ns,d

ifficultie

s,co

rne

r-cases,

•h

avete

chn

icalbackgro

un

dto

kno

wte

chn

icaldifficu

lties,

•co

mm

un

icate(fo

rmal)sp

ecificatio

nto

custo

me

r,

•“te

st”o

wn

un

de

rstand

ing

by

asking

mo

req

ue

stion

s.

→i.e

.toe

licitth

ere

qu

irem

en

ts.

Go

al:au

tom

ateo

pe

nin

g/clo

sing

of

am

aind

oo

rw

itha

ne

wso

ftware

.

Am

ade

up

dialo

gue

...

An

aly

st:S

oin

the

mo

rnin

g,yo

uo

pen

the

do

or

at

the

ma

inen

tran

ce?

Cu

stom

er:Yes,as

Itold

you.

A:E

verym

orn

ing?

C:O

fco

urse.

A:A

lsoo

nth

ew

eekend

s?

C:N

o,o

nw

eekend

s,the

entra

nce

stays

closed

.

A:A

nd

durin

gco

mp

an

yh

olid

ays?

C:T

hen

ita

lsorem

ain

sclo

sedo

fco

urse.

A:A

nd

ifyo

ua

reillo

ro

nva

catio

n?

C:T

hen

Mr.M

op

ens

the

do

or.

A:A

nd

ifM

r.Mis

no

ta

vaila

ble,to

o?

C:T

hen

the

firstclien

tw

illkno

cko

nth

ew

ind

ow

.

A:O

kay.N

ow

wh

at

exactly

do

es“m

orn

ing”

mea

n?

...(Lud

ewig

an

dLichter,20

13)

Ho

wC

an

Req

uirem

ents

En

gin

eering

Lo

ok

InP

ractice?

– 6 – 2016-05-12 – Sreana –

22

/3

7

•S

et

up

aco

rete

amfo

ran

alysis(3

to4

pe

op

le),in

clud

ee

xpe

rtsfro

mth

ed

om

ainan

dd

eve

lop

ers.A

nalysis

be

ne

fitsfro

mh

igh

est

skillsan

dstro

ng

exp

erie

nce

.

•D

urin

gan

alysis,talkto

de

cision

make

rs(m

anage

rs),do

main

exp

erts,an

du

sers.

Use

rscan

be

inte

rview

ed

by

ate

amo

f2

analysts,ca.9

0m

in.

•T

he

resu

lting

“rawm

aterial”

isso

rted

and

assesse

din

half-

or

full-d

ayw

orksh

op

sin

ate

amo

f6

-10p

eo

ple

.

Se

archfo

r,e.g., co

ntrad

iction

sb

etw

ee

ncu

stom

er

wish

es,an

dfo

rp

riorisatio

n.

No

te:T

he

custo

me

rd

ecid

es.A

nalysts

may

make

pro

po

sals(d

iffere

nt

op

tion

sto

cho

ose

from

),bu

tth

ecu

stom

er

cho

ose

s.(An

dth

ech

oice

isd

ocu

me

nte

d.)

•T

he

“rawm

aterial”

isb

asiso

fa

pre

limin

aryre

qu

irem

en

tssp

ecificatio

n(au

die

nce

:the

de

velo

pe

rs)with

op

en

qu

estio

ns.

An

alystsn

ee

dto

com

mu

nicate

the

req

uire

me

nts

spe

cification

app

rop

riately

(exp

lain,give

exam

ple

s,po

int

ou

tp

articular

corn

er-case

s).

Cu

stom

ers

with

ou

tstro

ng

math

s/com

pu

ter

scien

ceb

ackgrou

nd

areo

ften

ove

rstraine

dw

he

n“le

ftalo

ne”

with

afo

rmalre

qu

irem

en

tssp

ecificatio

n.

•R

esu

lt:dictio

nary

,spe

cified

req

uire

me

nts.

•M

any

custo

me

rsd

on

ot

wan

t(rad

ical)ch

ange

,bu

tim

pro

vem

en

t.

•G

oo

dq

ue

stion

s:Ho

ware

thin

gsd

on

eto

day?

Wh

atsh

ou

ldb

eim

pro

ved

?

Req

uirem

ents

Do

cum

ents

– 6 – 2016-05-12 – main –

23

/3

7

Dictio

na

ry

– 6 – 2016-05-12 – Sredocs –

24

/3

7

•R

eq

uire

me

nts

analysis

sho

uld

be

base

do

na

dictio

nary

.

•A

dictio

nary

com

prise

sd

efin

ition

san

dclarificatio

ns

of

term

sth

atare

rele

vant

toth

ep

roje

ctan

do

fw

hich

diffe

ren

tp

eo

ple

(inp

articular

custo

me

ran

dd

eve

lop

er)m

ayh

aved

iffere

nt

un

de

rstand

ings

be

fore

agree

ing

on

the

dictio

nary.

•E

ache

ntry

inth

ed

iction

arysh

ou

ldp

rovid

eth

efo

llow

ing

info

rmatio

n:

•te

rman

dsy

no

ny

ms

(inth

ese

nse

of

the

req

uire

me

nts

spe

cification

),

•m

ean

ing

(de

finitio

n,e

xplan

ation

),

•d

elim

inatio

ns

(wh

ere

no

tto

use

this

term

s),

•valid

ne

ss(in

time

,insp

ace,...),

•d

en

otatio

n,u

niq

ue

ide

ntifie

rs,...,

•o

pe

nq

ue

stion

sn

ot

yet

reso

lved

,

•re

lated

term

s,cross

refe

ren

ces.

No

te:e

ntrie

sfo

rte

rms

that

see

me

d“crystalcle

ar”at

firstsigh

tare

no

tu

nco

mm

on

.

•A

llwo

rko

nre

qu

irem

en

tssh

ou

ld,as

faras

po

ssible

,b

ed

on

eu

sing

term

sfro

mth

ed

iction

aryco

nsiste

ntly

and

con

seq

ue

ntly.

Th

ed

iction

arysh

ou

ldin

particu

larb

en

ego

tiated

with

the

custo

me

ran

du

sed

inco

mm

un

ication

(ifn

ot

po

ssible

,atle

astd

eve

lop

ers

sho

uld

stickto

dictio

nary

term

s).

•N

ote

:do

no

tm

ixu

pre

al-wo

rld/

do

main

term

sw

itho

ne

so

nly

“living”

inth

eso

ftware

.

Dictio

na

ryE

xam

ple

– 6 – 2016-05-12 – Sredocs –

25

/3

7

(Are

nis

et

al.,20

14)

Exam

ple

:Wire

less

Fire

Alarm

Sy

stem

•D

urin

ga

pro

ject

on

de

signin

ga

high

lyre

liable

,EN

-54

-25

con

form

ing

wire

less

com

mu

nicatio

np

roto

col,w

eh

adto

learn

that

the

rele

vant

com

po

ne

nts

of

afire

alarmsyste

mare

•te

rmin

alparticip

ants

(he

at/smo

kese

nso

rsan

dm

anu

alind

icators),

•re

pe

aters

(an

on

-term

inalp

articipan

t),

•an

da

cen

tralun

it(n

ot

ap

articipan

t).

•R

ep

eate

rsan

dce

ntralu

nit

arete

chn

icallyve

rysim

ilar,bu

tn

ee

dto

be

distin

guish

ed

tou

nd

erstan

dre

qu

irem

en

ts.T

he

dictio

nary

exp

lains

the

sete

rms.

Exce

rpt

from

the

dictio

nary

(ca.50

en

tries

into

tal):

Part

Ap

arto

fa

firealarm

syste

mis

eith

er

ap

articipan

to

ra

cen

tralun

it.

Re

pe

ater

Are

pe

ateris

ap

articipan

tw

hich

accep

tsm

essage

sfo

rth

ece

ntralu

nit

from

oth

erp

articipan

ts,o

rm

essage

sfro

mth

ece

ntralu

nit

too

the

rp

articipan

ts.

Ce

ntralU

nit

Ace

ntral

un

itis

ap

artw

hich

rece

ives

me

ssages

from

diffe

ren

tassign

ed

particip

ants,

as-se

sses

the

me

ssages,an

dre

acts,e.g.b

yfo

rward

ing

top

erso

ns

or

op

tical/acustic

signallin

gd

evice

s.

Term

inalP

articipan

tA

term

inalp

articipan

tis

ap

articipan

tw

hich

isn

ot

are

pe

ater.E

achte

rmin

alpartic-

ipan

tco

nsists

of

exactly

on

ew

irele

ssco

mm

un

ication

mo

du

lean

dd

evice

sw

hich

pro

vide

sen

sor

and

/or

signallin

gfu

nctio

nality.

Req

uirem

ents

Sp

ecifica

tion

– 6 – 2016-05-12 – Sredocs –

26

/3

7

spe

cification

—A

do

cum

en

tth

atsp

ecifie

s,

•in

aco

mp

lete

,pre

cise,ve

rifiable

man

ne

r,

the

•re

qu

irem

en

ts,de

sign,b

eh

avior,o

ro

the

rch

aracteristics

of

asyste

mo

rco

mp

on

en

t,

and

,ofte

n,th

ep

roce

du

res

for

de

term

inin

gw

he

the

rth

ese

pro

vision

sh

aveb

ee

nsatis-

fied

.IE

EE

610

.12( 19

90

)

softw

arere

qu

irem

en

tssp

ecificatio

n(S

RS

)—D

ocu

me

ntatio

no

fth

ee

ssen

tialreq

uire

-m

en

ts(fu

nctio

ns,p

erfo

rman

ce,d

esign

con

straints,an

dattrib

ute

s)of

the

softw

arean

dits

exte

rnalin

terface

s.IE

EE

610

.12(19

90

)

– 6 – 2016-05-12 – Sredocs –

27

/3

7

The In

stitu

te o

f Ele

ctric

al a

nd E

lectro

nic

s E

ngin

eers

, Inc.

345 E

ast 4

7th

Stre

et, N

ew

York

, NY

10017-2

394, U

SA

Copyrig

ht ©

1998 b

y th

e In

stitu

te o

f Ele

ctric

al a

nd E

lectro

nic

s E

ngin

eers

, Inc.

All rig

hts

reserve

d. P

ublis

hed 1

998. P

rinte

d in

the U

nite

d S

tate

s o

f Am

eric

a.

ISB

N 0

-7381-0

332-2

No p

art o

f this

public

atio

n m

ay b

e re

pro

duced in

any fo

rm, in

an e

lectro

nic

retrie

val s

yste

m o

r oth

erw

ise, w

ithout th

e p

rior

writte

n p

erm

issio

n o

f the p

ublis

her.

IEE

E S

td 8

30-1

998

(Revis

ion o

f

IEE

E S

td 8

30-1

993)

IEE

E R

eco

mm

en

ded

Pra

ctic

e fo

r S

oftw

are

Req

uire

men

ts

Sp

eciÞ

catio

ns

Sponsor

So

ftware

En

gin

eerin

g S

tan

dard

s C

om

mitte

eo

f the

IEE

E C

om

pu

ter S

ocie

ty

Appro

ved 2

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une 1

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A S

tan

dard

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stra

ct:

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e c

on

ten

t an

d q

ua

lities o

f a g

oo

d s

oftw

are

req

uire

me

nts

sp

ecific

atio

n (S

RS

) are

de

-

scrib

ed

an

d s

eve

ral s

am

ple

SR

S o

utlin

es a

re p

rese

nte

d. T

his

reco

mm

en

de

d p

ractic

e is

aim

ed

at

sp

ecify

ing

req

uire

me

nts

of s

oftw

are

to b

e d

eve

lop

ed

bu

t als

o c

an

be

ap

plie

d to

assis

t in th

e s

ele

c-

tion

o

f in

-ho

use

a

nd

co

mm

erc

ial

so

ftwa

re p

rod

ucts

. G

uid

elin

es fo

r co

mp

lian

ce

w

ith IE

EE

/EIA

12

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7.1

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97

are

als

o p

rovid

ed

.

Ke

yw

ord

s:

co

ntra

ct, c

usto

me

r, pro

toty

pin

g, s

oftw

are

req

uire

me

nts

sp

ecific

atio

n, s

up

plie

r, syste

m

req

uire

me

nts

sp

ecific

atio

ns

Stru

cture

of

aR

equ

iremen

tsD

ocu

men

t:E

xam

ple

– 6 – 2016-05-12 – Sredocs –

28

/3

7

1IN

TR

OD

UC

TIO

N

1.1P

urp

ose

1.2A

cron

ym

san

dD

efin

ition

s1.3

Re

fere

nce

s1.4

Use

rC

haracte

ristics

2F

UN

CT

ION

AL

RE

QU

IRE

ME

NT

S

2.1

Fun

ction

Se

t1

2.2

etc.

3R

EQ

UIR

EM

EN

TS

TO

EX

TE

RN

AL

INT

ER

FAC

ES

3.1

Use

rIn

terface

s3

.2In

terface

sto

Hard

ware

3.3

Inte

rfaces

toS

oftw

areP

rod

ucts

/S

oftw

are/

Firm

ware

3.4

Co

mm

un

ication

Inte

rfaces

4R

EQ

UIR

EM

EN

TS

RE

GA

RD

ING

TE

CH

NIC

AL

DA

TA

4.1

Vo

lum

eR

eq

uire

me

nts

4.2

Pe

rform

ance

4.3

etc.

5G

EN

ER

AL

CO

NS

TR

AIN

TS

AN

DR

EQ

UIR

EM

EN

TS

5.1

Stan

dard

san

dR

egu

lation

s5

.2S

trategic

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nstrain

ts5

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ardw

are5

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oftw

are5

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om

patib

ility5

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ost

Co

nstrain

ts5

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ime

Co

nstrain

ts5

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tc.

6P

RO

DU

CT

QU

AL

ITY

RE

QU

IRE

ME

NT

S

6.1

Availab

ility,Re

liability,R

ob

ustn

ess

6.2

Se

curity

6.3

Main

tainab

ility6

.4P

ortab

ility6

.5e

tc.

7F

UR

TH

ER

RE

QU

IRE

ME

NT

S

7.1S

ystem

Op

eratio

n7.2

Cu

stom

isation

7.3R

eq

uire

me

nts

of

Inte

rnalU

sers

( Lud

ew

igan

dL

ichte

r,20

13)b

ased

on

(IEE

E,19

98

)

Co

nten

t

– 6 – 2016-05-12 – Scontent –

29

/3

7

•In

trod

uctio

n

•V

ocab

ulary

:Re

qu

irem

en

ts(A

nalysis)

•U

sages

of

Re

qu

irem

en

tsS

pe

cification

s

•R

eq

uire

me

nts

Sp

ecificatio

n

•D

esire

dP

rop

ertie

s

•K

ind

so

fR

eq

uire

me

nts

•A

nalysis

Tech

niq

ue

s

•D

ocu

me

nts

•D

iction

ary

•S

pe

cification

•S

pe

cification

Lan

gu

ages

•N

aturalL

angu

age

Sp

ecifica

tion

La

ng

uages

– 6 – 2016-05-12 – main –

30

/3

7

Req

uirem

ents

Sp

ecifica

tion

La

ng

uage

– 6 – 2016-05-12 – Sspeclang –

31/

37

spe

cification

lang

uage

—A

langu

age,o

ften

am

achin

e-p

roce

ssible

com

bin

ation

of

nat-

uralan

dfo

rmallan

guage

,use

dto

exp

ress

the

req

uire

me

nts,d

esign

,be

havio

r,or

oth

er

characte

risticso

fa

system

or

com

po

ne

nt.

For

exam

ple

,ad

esign

langu

ageo

rre

qu

irem

en

tssp

ecificatio

nlan

guage

.Co

ntrast

with

:p

rogram

min

glan

guage

;qu

ery

langu

age.

IEE

E6

10.12

(199

0)

req

uire

me

nts

spe

cification

lang

uage

—A

spe

cification

langu

agew

ithsp

ecialco

nstru

ctsan

d,so

me

time

s,verificatio

np

roto

cols,u

sed

tod

eve

lop

,analy

ze,an

dd

ocu

me

nt

hard

-w

areo

rso

ftware

req

uire

me

nts.

IEE

E6

10.12

(199

0)

Na

tura

lL

an

gu

age

Sp

ecifica

tion

(Ludew

igand

Lich

ter,

2013)

base

d

on

(Rupp

and

die

SO

PH

ISTen,2009

)

– 6 – 2016-05-12 – Sspeclang –

32

/3

7

rule

exp

lanatio

n,e

xamp

le

R1

State

each

req

uire

me

nt

inactive

voice

.N

ame

the

actors,in

dicate

wh

eth

er

the

use

ro

rth

esyste

md

oe

sso

me

thin

g.No

t“th

eite

mis

de

lete

d”.

R2

Exp

ress

pro

cesse

sb

yfu

llverb

s.N

ot

“is”,“has”,b

ut

“read

s”,“create

s”;fullve

rbs

req

uire

info

rmatio

nw

hich

de

scribe

the

pro

cess

mo

rep

recise

ly.No

t“w

he

nd

atais

con

sisten

t”b

ut

“after

pro

gramP

has

che

cked

con

sisten

cyo

fth

ed

ata”.

R3

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ver

inco

mp

lete

lyd

efin

ed

verb

s .In

“the

com

po

ne

nt

raises

ane

rror”,

askw

ho

mth

em

essage

isad

dre

ssed

to.

R4

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ver

inco

mp

lete

con

ditio

ns .

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nd

ition

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fth

efo

rm“if-e

lse”n

ee

dd

escrip

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so

fth

eif-

and

the

the

n-case

.

R5

Disco

ver

un

iversal

qu

antifie

rs .A

rese

nte

nce

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ith“n

eve

r”,“always”,“e

ach”,“any”,“all”

really

un

iversally

valid?

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“all”re

allyallo

rare

the

ree

xcep

tion

s.

R6

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eck

no

min

alisation

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ou

ns

like“re

gistration”

ofte

nh

ide

com

ple

xp

roce

sses

that

ne

ed

mo

red

etaile

dd

escrip

tion

s;the

verb

“registe

r”raise

sap

pro

priate

qu

estio

ns:w

ho

,wh

ere

,for

wh

at?

R7

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cogn

isean

dre

fine

un

clear

sub

stantive

s.Is

the

sub

stantive

use

das

age

ne

ricte

rmo

rd

oe

sit

de

no

teso

me

thin

gsp

ecific?

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ser”

gen

eric

or

isa

me

mb

er

of

asp

ecific

classes

me

ant?

R8

Clarify

resp

on

sibilitie

s.If

the

spe

cification

saysth

atso

me

thin

gis

“po

ssible”,“im

po

ssible”,o

r“m

ay”,“sho

uld

”,“mu

st”h

app

en

,clarify

wh

ois

en

forcin

go

rp

roh

ibitin

gth

eb

eh

aviou

r.

R9

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ntify

imp

licitassu

mp

tion

s .Te

rms

(“the

firew

all”)that

aren

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exp

laine

dfu

rthe

ro

ften

hin

tto

imp

licitassu

mp

tion

s(h

ere

:the

rese

em

sto

be

afire

wall).

Na

tura

lL

an

gu

age

Pa

tterns

– 6 – 2016-05-12 – Sspeclang –

33

/3

7

Natu

rallangu

agere

qu

irem

en

tscan

be

(tried

tob

e)writte

nas

anin

stance

of

the

patte

rn“〈A

〉〈B

〉〈C

〉〈D

〉〈E

〉〈F

〉.”(G

erm

angram

mar)w

he

re

Aclarifie

sw

he

nan

du

nd

er

wh

atco

nd

ition

sth

eactivity

takes

place

Bis

MU

ST

(ob

ligation

),SH

OU

LD

(wish

),or

WIL

L(in

ten

tion

);also

:MU

ST

NO

T(fo

rbid

de

n)

Cis

eith

er

“the

system

”o

rth

eco

ncre

ten

ame

of

a(su

b-)syste

m

Do

ne

of

thre

ep

ossib

ilities:

•“d

oe

s”,de

scriptio

no

fa

system

activity,•

“offe

rs”,de

scriptio

no

fa

fun

ction

offe

red

by

the

system

toso

me

bo

dy,

•“is

able

if”,u

sageo

fa

fun

ction

offe

red

by

ath

irdp

arty,un

de

rce

rtainco

nd

ition

s

Ee

xten

sion

s,inp

articular

ano

bje

ct

Fth

eactu

alpro

cess

wo

rd(w

hat

hap

pe

ns)

(Ru

pp

and

die

SO

PH

ISTe

n,2

00

9)

Exam

ple

:

Afte

ro

fficeh

ou

rs(=

A),th

esyste

m(=

C)sh

ou

ld(=

B)

offe

rto

the

op

erato

r(=

D)

ab

ackup

(=F

)of

allne

wre

gistration

sto

ane

xtern

alme

diu

m(=

E).

Oth

erP

attern

Exa

mp

le:R

FC

21

19

– 6 – 2016-05-12 – Sspeclang –

34

/3

7

Network Working Group S. Bradner

Request for Comments: 2119 Harvard University

BCP: 14 March 1997

Category: Best Current Practice

Key words for use in RFCs to Indicate Requirement Levels

Status of this Memo

This document specifies an Internet Best Current Practices for the

Internet Community, and requests discussion and suggestions for

improvements. Distribution of this memo is unlimited.

Abstract

In many standards track documents several words are used to signify

the requirements in the specification. These words are often

capitalized. This document defines these words as they should be

interpreted in IETF documents. Authors who follow these guidelines

should incorporate this phrase near the beginning of their document:

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL

NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and

"OPTIONAL" in this document are to be interpreted as described in

RFC 2119.

Note that the force of these words is modified by the requirement

level of the document in which they are used.

1. MUST This word, or the terms "REQUIRED" or "SHALL", mean that the

definition is an absolute requirement of the specification.

2. MUST NOT This phrase, or the phrase "SHALL NOT", mean that the

definition is an absolute prohibition of the specification.

3. SHOULD This word, or the adjective "RECOMMENDED", mean that there

may exist valid reasons in particular circumstances to ignore a

particular item, but the full implications must be understood and

carefully weighed before choosing a different course.

4. SHOULD NOT This phrase, or the phrase "NOT RECOMMENDED" mean that

there may exist valid reasons in particular circumstances when the

particular behavior is acceptable or even useful, but the full

implications should be understood and the case carefully weighed

before implementing any behavior described with this label.

Bradner Best Current Practice [Page 1]

RFC 2119 RFC Key Words March 1997

5. MAY This word, or the adjective "OPTIONAL", mean that an item is

truly optional. One vendor may choose to include the item because a

particular marketplace requires it or because the vendor feels that

it enhances the product while another vendor may omit the same item.

An implementation which does not include a particular option MUST be

prepared to interoperate with another implementation which does

include the option, though perhaps with reduced functionality. In the

same vein an implementation which does include a particular option

MUST be prepared to interoperate with another implementation which

does not include the option (except, of course, for the feature the

option provides.)

6. Guidance in the use of these Imperatives

Imperatives of the type defined in this memo must be used with care

and sparingly. In particular, they MUST only be used where it is

actually required for interoperation or to limit behavior which has

potential for causing harm (e.g., limiting retransmisssions) For

example, they must not be used to try to impose a particular method

on implementors where the method is not required for

interoperability.

7. Security Considerations

These terms are frequently used to specify behavior with security

implications. The effects on security of not implementing a MUST or

SHOULD, or doing something the specification says MUST NOT or SHOULD

NOT be done may be very subtle. Document authors should take the time

to elaborate the security implications of not following

recommendations or requirements as most implementors will not have

had the benefit of the experience and discussion that produced the

specification.

8. Acknowledgments

The definitions of these terms are an amalgam of definitions taken

from a number of RFCs. In addition, suggestions have been

incorporated from a number of people including Robert Ullmann, Thomas

Narten, Neal McBurnett, and Robert Elz.

Tell

Th

emW

ha

tYo

u’ve

To

ldT

hem

...

– 6 – 2016-05-12 – Sttwytt –

35

/3

7

•R

eq

uire

me

nts

Do

cum

en

tsare

imp

ortan

t—

e.g.,fo

r

•n

ego

tiation

,de

sign&

imp

lem

en

tation

,do

cum

en

tation

,te

sting,d

elive

ry,re-u

se,re

-imp

lem

en

tation

.

•A

Re

qu

irem

en

tsS

pe

cification

sho

uld

be

•co

rrect,co

mp

lete

,rele

vant,co

nsiste

nt,n

eu

tral,traceab

le,o

bje

ctive.

No

te:vagu

evs.ab

stract.

•R

eq

uire

me

nts

Re

pre

sen

tation

ssh

ou

ldb

e

•e

asilyu

nd

erstan

dab

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recise

,easily

main

tainab

le,e

asilyu

sable

•D

isting

uish

•h

ard/

soft,

•fu

nctio

nal/

no

n-fu

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•o

pe

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tacit.

•It

isth

etask

of

the

analy

stto

elicit

req

uire

me

nts.

•N

aturallan

guage

isin

he

ren

tlyim

pre

cise,co

un

ter-m

easu

res:

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aturallan

guage

patte

rns.

•D

on

ot

un

de

restim

ateth

evalu

eo

fa

goo

dd

iction

ary.

Referen

ces

– 6 – 2016-05-12 – main –

36

/3

7

Referen

ces

– 6 – 2016-05-12 – main –

37

/3

7

Are

nis,S

.F.,We

stph

al,B.,D

ietsch

,D.,M

uñ

iz,M.,an

dA

nd

isha,A

.S.(2

014

).T

he

wire

less

firealarm

system

:E

nsu

ring

con

form

ance

toin

du

strialstand

ards

thro

ugh

form

alverificatio

n.

InJo

ne

s,C.B

.,Pih

lajasaari,P.,and

Su

n,

J.,ed

itors,FM

2014

:Form

alM

etho

ds

-19

thIn

terna

tion

alS

ymp

osium

,Sin

gap

ore,M

ay

12-16,20

14.P

roceed

ings,

volu

me

84

42

of

LNC

S,p

ages

65

8–

67

2.S

prin

ger.

Bro

oks,F.P.(19

95

).Th

eM

ythica

lMa

n-M

on

th:E

ssays

on

So

ftwa

reE

ngin

eering,A

nn

iversary

Editio

n.

Ad

diso

n-W

esle

y.

Gacitu

a,R.,M

a,L.,N

use

ibe

h,B

.,Piw

ek,P.,d

eR

oe

ck,A.,R

ou

nce

field

,M.,S

awye

r,P.,Willis,A

.,and

Yang,H

.(2

00

9).

Makin

gtacit

req

uire

me

nts

exp

licit.talk.

IEE

E(19

90

).IE

EE

Sta

nd

ard

Glo

ssary

of

So

ftwa

reE

ngin

eering

Termin

olo

gy.S

td6

10.12

-199

0.

IEE

E(19

98

).IE

EE

Reco

mm

end

edP

ractice

for

So

ftwa

reR

equirem

ents

Sp

ecificatio

ns.

Std

83

0-19

98

.

Lud

ew

ig,J.and

Lich

ter,H

.(20

13).

So

ftwa

reE

ngin

eering.

dp

un

kt.verlag,3

.ed

ition

.

Ru

pp

,C.an

dd

ieS

OP

HIS

Ten

(20

09

).R

equirem

ents-E

ngin

eering

und

-Ma

na

gemen

t.H

anse

r,5th

ed

ition

.